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1985 1985: Insects and Diseases of Southern Forests Louisiana State University and Agricultural & Mechanical College

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INSECTS AND DISEASES OF FORESTSS O U T H E R N

SCHOOL OF FORESTRY WILDLIFE, AND FISHE R IE S lOUISIANA EXPERIMENTAGRICULTURAL STATION LOUISIANA STATE UNIVERSITY AGRICULTURAL CENTER

34th Annual Forestry Symposium

1985

INSECTS AND DISEASES OF SOUTHERN FORESTS

EDITED BY

RICHARD A. GOYER Professor of Entomology and

JOHN P. JONES Associate Professor of Plant Pathology and Crop Physiology

Published through the academic direction of SCHOOL OF FORESTRY, WILDLIFE, AND FISHERIES

LOUISIANA STATE UNIVERSITY AGRICULTURAL CENTER

In cooperation with

LOUISIANA STATE UNIVERSITY AGRICULTURAL CENTER TABLE OF CONTENTS

Page

iii John P. Jones

Acknowledgments...... iv

SESSION I

How Insect and Disease Problems Manifest Themselves in the Landscape and Urban Forestry Industry...... 2

Managing Forest Insect and Disease Losses...... 5

Impact of Insects and Diseases on Large Industrial 8 and Stephen W. Coleman

Recent Advances in Insect Control 16

Nursing Diseases - Outplanting Survival as Affected by 24

SESSION II

A Decision Support System for 35 Michael C. Saunders, Koushen D. Loh, Edward J. Rykeil, Thomas L. Payne, Paul E. Pulley, and Lorinda C. Hu

A View of Resistance to Fusiform 47

Influence of Forestry Practices on Bark Beetle Populations: 52

Prospects for Oak Wilt Control in 60

i Mechanisms of Tree Resistance to Bark Beetles: 69 T. D. Paine, and M. P. Lih

Recent Advances in Control of 83

SESSION III

Utilization of Pheromones in C. Wayne Berisford, 92 Gary L. DeBarr, and Thomas L. Payne

Biological and Natural Control of Forest Insects — An Update...... 97

Decreasing Losses Due to Wood Deterioration Through Proper Forestry Practices...... Terry L. Amburgey 105

Implementing Forest Pest Management: The Forester's Role...... Ronald F. Billings 111

Making Management Decisions Before Establishing Slash Pine Plantations in Areas Where Fusiform Rust is a Hazard...... 120

ii FOREWORD

The problem of insects in southern forests has not been addressed by this Symposium series since 1965, and diseases never have been so addressed. It was felt that a consideration of both of these subjects would be timely. In the twenty years since insects were discussed in this series a number of advances have been made - both by entomologists and insects.

Insect damage and control are, most immediately, becoming one of the forestry industry's largest concerns as noted in the opening session of the Symposium. The applied chemical control of insects in seed orchards has become very important in the last two decades because of increasing demand for genetically improved pine seedlings for regeneration. Two major research and development programs aimed at pine bark beetles have enhanced our ability to coordinate preventative management with existing control strategies. Recently, host tree resistance, insect pheromones, and natural and biological control organisms have received renewed research efforts. Lastly, the aspect of technology transfer through user-friendly computer systems has vastly improved the ability of the practicing forester to utilize the products of technical research.

Diseases have an important impact on all aspects of the forestry industry. Fusiform rust is easily the single most devastating disease in southern pine forests. Recently some very promising advances in control strategies have been reported, particularly in the genetics of resistance to fusiform rust. Some very useful mathematical models for predicting the impact of fusiform rust in plantations also have been developed. Longleaf pine is a potential alternative to loblolly or slash pine in areas of high fusiform rust hazard, particularly in light of some of the recent advances in control of brown spot needle blight. Equally important to the forest industry, probably, is wood decay. It is quite difficult to assess the loss due to wood decay because it occurs at every step of the forestry industry from standing trees to in-service wood. Some of the steps that can be taken to alleviate losses due to wood decay are discussed here. The problem of oak wilt has taken on a new dimension with the recognition of an oak wilt epidemic in Texas. Oaks are the dominant tree in central Texas and this disease occurs over large areas including urban as well as rural settings. The situation in Texas is unusual in several respects and, we thought, of interest to southern foresters.

It is the intent of this Symposium to present us~able information to the practicing forester. While theoretical or experimental aspects of forest insects and diseases are included as interesting and important, the payoff is in the profitable application of these aspects by practicing foresters. We trust that this volume will be useful in that respect.

Richard A. Goyer

John P. Jones

iii ACKNOWLEDGMENTS

We extend our appreciation to all participants in the Symposium, especially the speakers and moderators. Several companies provided exhibits and/or financial support of the Symposium. These were: Forestry Suppliers, General Supply Co., Ben Meadows Co., Pennwalt Corp., Mobay Co., and Bennett and Peters Co.

Drs. Allen Main and Robert Mills, Louisiana Cooperative Extension Service, were of invaluable assistance in organizing and printing and distribution of the program. Ms. Julie Marotz was instrumental in the typing of the manuscript.

iv SESSION I

Moderator:

Dr. Harvey Toko Staff Director USFS, Forest Insect and Disease Management Atlanta, GA HOW INSECT AND DISEASE PROBLEMS MANIFEST THEMSELVES IN THE LANDSCAPE AND URBAN FORESTRY INDUSTRY

Richard Humphreys Landscape Architect and Arborist 806 W. Roosevelt St. Baton Rouge, LA 70802

This is really quite an honor for me to be asked to address the 34th Annual Louisiana Forestry Symposium, especially since I am not a forester. However, a few aspects of my work are seen in forest environments. I am licensed as a landscape architect and as a arboriculturalist and have an ornamental and turf pesticide license that allows me to treat diseases of landscape plant materials. My work often includes developments on wooded sites, where some of the existing trees will be retained, or correcting prob­ lems that are occurring with landscape plant materials. Unlike forestry situations, where the concern is for the cultivation of a great many trees as cost efficiently as possible. My concern is for only one or a few plants, and cost is less important. Many of the plants that I work with have been cul­ tivated over a long period of time and represent considerable effort and expense. This makes them unreplaceable and precious as a site amenity.

Unfortunately, arboriculture in this urban-suburban context of small lots and intense land use has not kept pace with forestry and horticulture in it's development of new methods. I suspect that this is due in part to the fact that commercial arboriculture is a service industry. Therefore, it does not generate a crop and product/profit from which research funds can be drawn.

Obviously forestry and general horticulture practices have been adapted to arboriculture, and have given us solutions to some of the problems that we see. But what do I do? As an arborist, I am a technician. I take my client's disease problems to one of the forest experts at the extension service, and they recommend a treatment. However, the disease problems are often only the aftermath to environmental conditions that cannot be corrected by the time the damage is apparent. Often I find that I am being asked to correct a problem rather than prevent one, and to treat a symptom rather than a cause. The complex types of environmental stresses that occur today exacerbate the forest and horticulture diseases that we see in the urban context. As a result the arboriculture industry needs a more diverse "tool box" to deal with these problems, and to a certain extent we have found one. The following items are some of the developments that have helped us to expand our capabilities.

P.P.D or People Pressured Diseases.— This concept is the recognition that the stress that occurs to trees as a site is developed can cause their decline. This concept when viewed with a broader scope can open a wide list of potential stresses to consider including such diverse items as: the stresses caused by restricted root zones, as in garage top planters; the effects of air, water or soil pollution; or, the effects of artificial heat and light sources, such as from reflective surfaces, heat pumps and other types of equipment. These are only a few of an endless list of items that our technological culture imposes on the plant world. Notice that these problems are not of a biotic nature. Yet in their milder forms these stresses can weaken a host plant to

2 the point that various biotic disease problems will develop. In this situation treating the pest problem is treating a symptom, not a cause.

This broad concept of P.P.D. points to a possible solution. Now, growers and landscape designers must recognize not only the plants best adapted to a microclimate in the traditional sense of soil, light, temperature and water compatibility but also consider artificial stresses and develop and use species that show superior tolerances to these various stresses.

Pesticide use.— Another change in the industry is the increasing con- cerns for public safety, and the wide spread use of pesticides. Professionals in this industry must be concerned not only with the proper use of chemicals, but also with the potential damage caused by nuisance suits from adjacent property owners, who feel that spray drift may pose a hazard. Defending such a suit can be very costly even if no damages are proven. Recognition of the benefits of frequent site visits and the use of low volumes of pesticides reduces the total amount of pesticides used and prevents unnecessary or exces­ sive spraying. This method is accomplished by frequent site visits for more careful monitoring of potential pests and spot spraying to control localized outbreaks of pests before a large population can develop.

The development of injection techniques for applying chemical directly into the vascular system of the trees has been significant. This method developed over a long time, but most of the current technology was developed in response to dutch elm disease, a fungus that could not be treated until systemic fungicides were developed. The Mauget Company of Burbank, California, is one of the leading developers of injection systems. Currently they offer 2 types of insecticides, 2 fungicides, 1 bacteriacide and 4 micronutrients to correct nutritional problems. These types of products allow us to treat disease that often would not respond to conventional methods of treatment, such as foliar applications of pesticides. They have the added advantage of allowing us to use some very potent chemicals in densely populated areas, because the chemical is in a closed system of application, i.e., it is not released into the environment. Instead it biodegrades gradually in the tissues of the injected tree.

Another tool, the shigometer, developed by Dr. Alex Shigo of the U.S. Forest Service, was introduced in 1968. It is a digital pulse electrical resistance meter introduced as a tool for detecting and monitoring decay in timbers and beams. This tool was quickly adapted to investigating cavities and heartwood rot that could not be visually inspected. This was done to he p identify trees that might pose a safety hazard in area of high use. Almost immediately investigations were started trying to find a correlation between cambium conductivity of various plants and plant vitality. The debate on this type of application has continued ever since. Currently many practitioners believe that this does work and quite a few of these units are being used n the field. I would like to conclude this paper by saying that having been in a dual position in this industry I have had the opportunity to monitor the condition of trees from the beginning of a project's development through the laying of the last brick and for years after. This experience has led me to believe that the arborist or urban forester needs to be assisting designers and engineers in the entire development process. Often, design professionals make decisions

3 about trees based strictly on appearances with no knowledge of soundness, stress tolerance, or potential disease problems. Similarly, they do not set any standards other than minimal ones for developing around trees. This is largely due to ignorance and would change if arboriculturalists would make greater efforts to provide consulting services. I find that I can give my clients the best results when I am able to participate in the project while it's still on the drawing boards, and when I'm available to them at every stage of development, where trees are involved.

4 MANAGING FOREST INSECT AND DISEASE LOSSES

Burton D. Weaver, Jr. Weaver Brothers Land & Timber Company Flora, Louisiana

First I would like to give you an overview of Weaver Bros. Land and Timber Co's, structure, so that I may place our operation in perspective. My Family began our Louisiana operation in 1900. In 1974 we went through a Section 333 liquidation which placed the stockholders in possession of their acreage. This resulted in my personal family owning approximately 5,000 acres and our managing another 11,000 acres, or so, for absentee owners. We live, and our office is in Flora, Louisiana, which is in south Natchitoches Parish. My father lived in Flora all his adult life, and I have lived there all of my life except for my time at Louisiana State University Forestry School, and a tour in the United States Marine Corps. All of the land we own, and manage, is within nine miles of Flora. The timber is primarily loblolly pine, with some longleaf and shortleaf pine. The creek bottoms contain mixed hardwood. We manage for large pine sawlogs, because we feel this is the best use of our land, and for the higher prices these products return on the investment. The increasing market for pine pulpwood and chips has caused us to emphasize pulpwood products more than merely as a product of thinnings. We also sell hardwood pulp, crossties, poles and hardwood logs.

Now as to damage, or impact, from insects and disease. The most damaging, nothing else compares, is southern pine beetle (SPB). I will discuss this a little later. Other agents which cause us harm are beavers and storms.

Beavers have caused a significant degree of damage from their damming streams and the resulting flooding of hardwood areas. We have tried breaking dams, shooting beaver, and extensive trapping of the persistant little crea­ tures. We have eliminated many beavers but the population always re­ establishes itself. In the end they have always prevailed. My recommendation is to use the resulting ponds as duck hunting areas.

On the night of May 19, 1983 our area experienced a phenomena known as a steady state thunderstorm, a super cell, or more precisely a mesoscale cyclone. Natchitoches Parish received much less damage than the area to our east in Winn, Caldwell and La Salle Parishes. But, we did receive extensive, scattered damage to both pine and hardwood timber. The damage was greatest in some recently thinned pine areas. Due to the scattered nature of the blowdown, we had difficulty salvaging the wood. Several of these affected areas developed southern pine beetle build up. I have wondered if there is any relationship between this storm and the build up of southern pine beetle which occurred the next year, and is continuing.

Now to the southern pine beetle. I will not try to tell you how to identify SPB in the forest. This has been covered many times. But I would suggest you obtain a copy of the December, 1984, Forest Landowner, published by the Third Forest Committee of the Louisiana Forestry Association. This news­ letter, in pamphlet form, can serve as a handy, concise guide for reference, or for use by those not familiar with southern pine beetle.

5 We have had small, scattered, infrequent, infestation of SPB in our area for many years. These were usually in the vicinity of a pine tree killed by lightning. The SPB were in association with other organisms which killed pine trees. The severity of these SPB infestation seemed to be related to their build up at the time. Evidently these particular bark beetles are always present in the forest, and assume outbreak proportion due to some factor, or factors, which causes their population to increase.

In August, 1984, we were informed of several SPB spots by the Office of Forestry. These outbreaks have been detected by one of their flights. The first spot we attempted to control was approximately 7-9 acres in size. The timber was mature loblolly pine. We moved in and cut the spot and the recom­ mended buffer zone. The sawlogs and pulp were removed. We returned several times as the SPB spread, using the same control method. To make a long story shorter, in the end the spot spread until the SPB destroyed all the timber on a 100 acre block.

At the present time we are working, or attempting to work, as the weather permits, on approximately 35 spots. These spots range in size from 3 or 4 acres, to one in excess of 200 acres. As you can gather this represents a great deal of loss to the small acreage on which we work. Also, we have found numerous SPB spots on land adjacent to our acreage. We have reported these infestations, and though some have been salvaged, many have been left to spread.

My biggest worry is SPB spots which we have not detected. We are finding new infestations weekly. Most of these areas, when found, have no brown tops, but are being eaten up by SPB. During January and February on warm days after freezing nights, I have found active beetles in the bark.

Most infestations we have found are in mature pine timber. Many of these trees are on land I manage for other people. The management plans I have written for these people recommended the removal of most of these larger trees. They have not followed my recommendations because of no real need for current income, or because they felt timber prices were too low.

We have located and are locating the SPB by a variety of means. Airplane observation of brown top pines, has been, and is, very valuable. Some have been found by us we ride the wood roads, and walk the woods. The most valuable source of information has been local people who spend time in the woods. Due to our good relations with hunters, and other local people, we are informed when they find dead pine timber. I would like to stress the benefits from having friends in the local rural area who hunt, or live near the wooded areas, and can be helpful, or harmful, to our efforts, based on their opinion of the land owner.

After finding SPB spots we have used all means possible to remove the infested timber from the woods. In our area, in the fall of 1984, and so far in 1985, the timber market for sawlogs and plywood has been poor. We have moved most of large logs for crossties. The tops and small material goes for pulpwood.

We know most of the area loggers through years of doing business with them, and being a member of the local community. We have always been fair with

6 these hard working people and treat them with honesty and respect. In return we get extra effort in doing a good job of cutting, logging, and marketing our wood products.

We have used the cut and leave method on some isolated spots. But frank­ ly, it is hard for me to have big green pine trees cut, and left in the woods. I respect this method, but still it goes against the grain, and all my train­ ing.

It would also be desirable to perform a normal harvest cut in the areas adjacent to the infestation. But we have found this, difficult, if not impos­ sible to carry out. We sell our sawlogs on a lump sum bid basis, and no buyer would be inclined to bid on an area with moving infestation.

To sum up, since receiving the invitation to appear at the symposium, I have learned a great deal about SPB. Unfortunately, it has been from personal contact with their damaging effects. We have improved our methods of locating SPB outbreaks, and securing loggers to remove the infested trees. Obviously we have no control over the market for the wood, or of the logging condition.

In retrospect, the best thing we could have done to mitigate the losses would have been to convince our clients to market their mature timber. This would have prevented a substantial loss in timber value because of the low prices we have received for the wood.

7 IMPACT OF INSECTS AND DISEASES ON

LARGE INDUSTRIAL FOREST LANDOWNERS

Richard R. Myers, District Forester, and Stephen W. Coleman, Regeneration Forester Boise Cascade Corporation DeRidder, Louisiana

Large industrial forest landowners generally establish the priorities of insect and disease threats by comparatively evaluating each insect or disease risk and assigning a corresponding economic value to these risks. Transforming insect and disease threats into potential financial costs is not a ruthless way to evaluate which piece of research is most worthy, but is the way which industrial field forestry managers can justify, to their superiors, that the threat is severe enought to allocate cash resources to fund research or control methods. It simply is a matter of trying to consider all the ramifications involved, then quantitatively supporting the risks in the language that finan­ cial officers understand and appreciate.

Generally, I will overview various ways that these problems impact large industrial forestland companies. I will deal principally with problems which inflict the most serious economic consequences in the Gulf Coastal Plain and principally those in commercial loblolly and slash pine forests.

As a managing field forester, I am not an entomologist or pathologist. Hence, I promise that I will not divulge any new scientific brilliance, but hope to give these scientists an idea concerning my impression of where the problem areas are in managing large industrial forestland bases. Most experi­ enced industrial foresters have dealt with these problems - many are recognized as experts, lots have more exposure than I do.

I will classify industrial forestland insect and disease problems into two broad groups. Insects and disease threats, based upon their potential finan­ cial impacts are placed in one of the two classes. Those threats with the most severe potential costs are placed in the first class; one which received considerable financial support from the industrial forestland manager. Into the second classification will go lesser threats and will include many small nuisance-type threats from insects and diseases.

Today, I will talk briefly about two groups of insect pests in my high- risk class. These two, the southern pine beetle (Dendroctonus frontalis Zimmermann) and cone and seed insects, collectively represent a material threat to large industrial forest landowners. Additionally, I will add fusiform rust (Cronartium fusiforme Hedge, and Hunt ex Cumm.) and would conditionally add Fomes annosus (Fr.) root rot to the high-risk classification (Robbins, 1984). The condition under which Fomes annosus would be added is that the landbase be composed of a high percentage of the high-risk soil types in which this fungal pathogen can create a volatile risk situation.

I will restrict my comments to the impact of those three pests: Fusiform rust, cone and seed insects, and the southern pine beetle. The limitation of time and space, and the wealth of more qualified scientific speakers later in

8 the program promise to provide this audience with greater details of these three and many other pests which impact southern forest landowners.

Fusiform Rust (Cronartium fusiforme Hedge, and Hunt ex Cumm.)

More documentation and scientific literature probably exists for fusiform rust than for any other disease common to the slash pine (Pinus elliottii Engel. Var. Elliottii) and loblolly pine (Pinus taeda L.) geographic range. The quantity of research is voluminous and deservedly so. This fungus impacts large industrial landowners' forest in many ways, ranging in severity from the slight destruction of tree form to the lethal infection of nearly every tree in a forest stand.

Fusiform rust attacks several species of southern pine, but is often considered most damaging to slash and loblolly (Phelps and Czabator, 1978). The mortality effect on southern pines is greatest in stands less than ten years old. Gall formations on trees in older stands result in deformities which weaken trees to the extent that economic management alternatives are often severely restricted in stands which are heavily infected.

The life cycle of Cronartium fusiform is complex but well documented. Often two years or longer is required for the rust's life cycle to go from the initial pine host, through the oak intermediate host back to the re-infection of pine. In early spring, enormous numbers of the commonly seen orange aeciospores begin their windborne migration to the surfaces of young oak leaves where they germinate and cause local infections (Phelps and Czabator, 1978). Seven to ten days later, small pustules bearing orange urediospores develop on the undersides of the infected oak leaves. Unusually within a week, brown, hairlike telia form on the undersurfaces of the oak leaves. Each telia consists of several hundred teliospores and may remain viable until early summer. Warm, humid weather promotes the germination of each teliospore which, in turn, releases 3 to 4 sporidia to infect susceptible pine tissue, completing the cycle.

The incidence and geographic distribution of fusiform rust in the early 1970's, is evidenced by the following isogram maps (Squillace, 1976). Loblolly and slash pine rust incidence in 8 to 12-year old stands was highest in Georgia, Alabama, South Carolina, and Mississippi. Louisiana showed a high incidence for slash and a low incidence for loblolly, while Florida showed the inverse. Also, the rust incidence was more severe on slash than on loblolly and Phelps (1976) remarked that his examination showed a higher overall incident rate and wider geographic distribution than a study done in the late 1930's (Phelps, 1976).

Today, efforts to reduce the harmful effects of fusiform rust are well established and wide ranging. Learning about the multitude of factors contributing to the increase in both the range and virulence of fusiform climatology, site, seed provenance, nursery management, and forest management continue to progress.

What does all this mean to large industrial forest managers? His manage­ ment philosophy is equally as difficult as the researchers' approach toward reducing the tightening stranglehold that fusiform rust has on southern for­ ests. Many things the managing forester can do to accelerate early plantation

9 growth amy also promote the infection and impact of fusiform rust on the same stand (Hollis, 1976). Genetics, thinning, fertilization, and other measures employed to enhance growth rate are sometimes reported to singly and/or collec­ tively worsen the stand's rust problem.

Emphasis of rust-free phenotype ortet selection for inclusion into tree improvement programs has made progress in reducing the infection rates in young stands. On the following graphs, Griggs and Schmidt (1976) demonstrate the comparison of susceptible, intermediate, and resistant families of slash pine in two locations - Gulfport, Mississippi, and Bogalusa, Louisiana. Similar graphs, loblolly represent two plantings in Bainbridge, Georgia.

Local seed sources and rust resistant seed are helping to control some rust problems. The common use of the fungicide Bayleton (reg. U.S. trademark) has given the nurseryman a strong tool to use in reducing nursery bed infection rates.

Powers, McClure, Knight, Dutrow (1975) dealt with the financial impact of fusiform rust in the South in their 1975 publication. Their approach was to use a weighted value per unit of fiber lost to fusiform rust. 1 will use their results and apply some simple extrapolation to project their 1972 loss values forward to 1985.

Example of Financial Losses from Fusiform Rust

Assumption:

1. Rust incidence accelerates at 2% per year (Powers, McClure, Knight, and Dutrow, 1975).

2. Nominal financial growth is 5% per year.

3. Thirteen years of time elapses.

4. 1972 "intermediate" loss was $28,000,000.

Projected F.V. of $28 million due to rust incidence increase equals $36.2 million.

Projected F.V. of $36.2 million due to 5% creep of per year equals $68.26 million.

If Powers, McClure, Knight, and Dutrow (1975) "high" loss of $35.5 million is used, and rust incidence rises at 3% per year under the above assump­ tions, the P.V. would be $98.2 million lost per year.

This illustration explains that fusiform rust costs southern forest landowners $68 to $98 million per year. If one uses a $70/cord marginal cost of wood as the unit costs of wood lost, the assumed loss then approaches $130 million. Regardless of which approach the readers selects, the cost to south­ ern forest landowners is formidable and growing.

10 Cone and Seed Insects

It has been estimated that nearly 25% of the annual southwide genetically- improved potential seed crop is lost to insect and disease problems. Recover­ ing this 25% loss in the operating area of the Western Gulf Forest Tree Improve­ ment Program tree improvement cooperative would allow essentially every acre of large industrial forestland to be regenerated with genetically-improved tree seedlings. The converse of this means that we are losing 25% of the genetic gain simply because we are unable to plant 25% of the forest base with improved seedlings.

In the future, state, federal, and private industrial seed orchards will produce enough seed to meet future needs even after losses to insects and disease. We will still lose 25% of our best genotypic material (that from advanced generations) to insect and disease problems unless new pest management technologies are discovered and implemented.

The following illustration shows a basic approach to determine the simple financial impact of losing 25% of the total annual seed orchard crop.

Assumption:

900 million seedlings are produced annually, southwide. 675 million seedlings are from seed orchard seed. (75%) 225 million seedlings are from woods-run seed. (25%) 800 seedlings will plant one acre. 1.3 cords per acre per year from woods-run seed source. 10% volume gain from seed orchard seed. Marginal cost of wood = $100/cord.

675 million seedlings = 843,750 acres planted with 800 trees per acre seed orchard seed.

225 million seedlings = 281, 250 acres planted with 800 trees per acre woods-run seed.

Therefore:

843,750 acres grow 1.43 cd./ac./yr. “ 1207 M cds./yr.

and,

281,250 acres could grow 1.43 cd./ac./yr. = 402 M cds./yr.

Potential = 1609 M cds./yr.

less:

0.13 cd./ac./yr. lost growth due to using non-seed orchard seed = (37) M cds./yr.

Actual = 1572 M cds./yr.

11 It is assumed that the 37 M cords lost due to 25% of the seed orchard seed having been lost to insect and disease problems will be replaced as purchased wood at the marginal cost of wood.

Therefore:

37 M cds. x $100/cd. ■ $3.7 million/year

$3.7 million is assumed to be the value of the 25% of seed orchard seed lost to insects and disease problems will be replaced as purchased wood at the marginal cost of wood.

Therefore:

37 M cds. x SlOO/cd. = $3.7 million/year

$3.7 million is assumed to be the value of the 25% of seed orchard seed lost to insects and disease. Thus, the average cost of the 1572 M cords grown per year is increased by $2.35 per cord.

$3.7 million = $2.35 increased average cost of wood 1572 M cords

This over-simplified illustration assumes that all seed lost to insects and disease is of equal quality. Actually, as orchard production levels exceed demand for seed, the poorest genotypic seed will not be planted, meaning that the 25% seed lost to insect and disease problems will continue to represent increasing quantities of the very best genotypic seed available. This, then, understates the financial impact from losses of seed orchard seed to insect and disease problems.

Southern Pine Beetle (Dendoctronus frontalis Zimmerman)

The southern pine beetle's ability to quickly build its populations and kill large numbers of trees make this pest one of the pine species most serious threats (Thatcher and Barry, 1982). Occurring from Pennsylvania to Texas and from New Mexico and Arizona to Honduras, this beetle cause forest managers to become concerned when even a small outbreak is reported. The forest manager's concern is well-founded. A ten-year average, from 1972 to 1982, shows that the southern pine beetle annually killed more than 200 million board feet of southern pine timber with one 4-year period having a loss as high as 4.5 billion board feet (Thatcher and Barry, 1982).

Southern pine beetle attacks are often accompanied by other risks from allied insects. The two most common pests that often work alongside the southern pine beetle are the numerous Ips bark beetles (Ips sp.) and the black turpentine beetle, Dendroctronus terebrans (Oliver) (Conner and Wilkinson. 1983).

Southern pine beetle populations are usually kept at acceptable levels by natural enemies including disease, parasites, and predators (Thatcher and Barry, 1982). Commonly, this naturally-occurring balance is upset when forest growth has been allowed to lose its vigor (Bennett, 1971). The insect's explosive population dynamics capabilities takes advantage of the low-vigor

12 stand, the beetle population becomes epidemic, and the past is out of its natural check.

Forest managers must design their management plan so that high forest vigor will be maintained. Most stands where outbreaks occur have basal areas which are greater than 150 square feet and often exceed 200 square feet (Bennett, 1971). Overstocking, lightning strikes, drought, fire, or logging damage to residuals all contribute to the encouragement of large beetle popula­ tion buildups. The responsible forest manager must keep their contributory effects in mind when developing both long-range and short-range operation plans. Otherwise, he is inviting the southern pine beetle populations to develop to epidemic levels in and around his managed forest base.

Southern pine beetle attacks have been reported in forest tree seed orchards where they occasionally will attack trees weakened by several means; including, but not limited to, fusiform rust, graft incompatibility, and water stress. These occurrences require swift action to prevent extreme financial losses which can have long-term impact.

The method of controlling southern pine beetle infestations by salvaging affected trees, cutting and leaving affected trees, or by chemical control, is usually determined by the severity of the attack. Obviously, even a small infestation occurring in a forest tree seed orchard deserves the utmost atten­ tion from the controlling manager. Conversely, a small infestation in an isolated timber tract will probably not receive the same acute and immediate attention.

Summary

Now, how do the aforementioned three insect and disease pests add up? The addition of my examples add up thusly:

Fusiform Rust Losses $130 million/yr. Cone & Seed Insect Losses (x 10 yrs.) 37 million/yr. Southern Pine Beetle Losses (@ $140/MBF) 28 milllon/yr. Total Financial Loss $195 million/yr.

The large industrial forest landowner must consider the probabilities of these pests becoming even greater threats to him. He must be aware of the pest, their life cycles, their population or infection dynamics, and current, acute problems which may be moving toward his managed land base. The existence or potential to acquire one or more of these pests alone or collectively, impact the manager's short-term and long-term decisions.

Short term, the large industrial forest manager must make alternative plans contingent on the impact of one or more severe outbreaks. For example, a critical beetle infestation would necessitate both salvaging large volumes of timber, and possibly leaving other stands uncut due to the limitation of local market conditions. In addition, if the market for excess sawtimber did exist, it would be reasonable to assume that the impact of the increased harvest would have a depressing affect on local market prices for timber products.

13 Another short-term effect for the large Industrial forest manager, is that of altering any computerized forest simulators or optimizers which must be adjusted to reflect the effect of the increased pest problem. The myriad of short-term effects is too lengthy to enumerate, but considerations for regeneration, budgeting, out-of-sequence harvesting, etc., will all have their impact.

Perhaps even more important, is the primary long-term effect conceived from the collective short-term impacts from insect and disease problems. Very few incidents of a severe nature or many episodes of a lesser degree of severi­ ty could, have, and will continue to change, major long-range alternatives for large integrated industrial forestland firms. These occasional catastrophic pest problems can be so threatening to the future alternatives of a firm or geographic operating area, that decisions to sell or relocate can become viable.

Literature Cited

Bennett, W.H. 1971. Silvicultural Techniques will help control bark beetles. s Proceedings, 1971 Southern Regional Technical Conference, Society of American Foresters.

Conner, M.D. and R.C. Wilkinson. 1983. Ips bark beetles in the south. U.S. Dept, of Agrlc., U.S. Forest Service. Forest Insect and Disease Leaflet No. 129.

Griggs, M.M. and R.A. Schmidt. 1976. Increase and spread of fusiform rust. Pages 32-38 Iji R.J. Dinus and R.A. Schmidt, eds. Management of fusiform rust in southern pines. Symp. Proc. U. of Fla., Gainesville. 163 p.

Hollis, C.A. 1976. Fusiform rust management strategies in concept: site hazard evaluation. Pages 90-97 in R.J. Dinus and R.A. Schmidt, eds. Management of fusiform rust in southern pines. U. of Fla., Gainesville. 163 p.

Lowe, W.J. 1985. Personal conversation. Texas Forest Service.

Phelps, W.R. and F.L. Czabator. 1978. Fusiform rust of southern pines. U.S. Dept, of Agric., U.S. Forest Service. Forest Insect and Disease Leaflet No. 26.

Powers, H.R. Jr., J.P. McClure, H.A. Knight, and G.F. Dutrow. 1975. Fusiform rust: forest survey incidence data and financial impact in the South. USDA For. Serv. Res. Pap. SE-127, 16 p. S.E. For. Exp. Stn., Asheville, N.C.

Robbins, K. 1984. Annosus root rot in Eastern conifers. USDA, U.S. Forest Service. Forest Insect and Disease Leaflet No. 76.

Squillace, A.E. 1976. Geographic patterns of fusiform rust infection in loblolly and slash pine plantations. USDA Forest Service REs. Note SE-232, 4 p. Asheville, N.C.

14 Thatcher, R.C. and P.J. Barry. 1982. Southern pine beetle. USDA For. Ser. Forest Insect and Disease Leaflet No. 49.

15 RECENT ADVANCES IN INSECT CONTROL IN PINE SEED ORCHARDS

Julie C. Weatherby Entomologist USDA-FS Pineville, LA

The economic benefits of tree improvement became apparent to southern foresters in the 1950's and early 1960's. By 1970, 6,033 acres of southern pine seed orchards had been established in the South. Many of these orchards began producing in the late 1960's or early 1970's. The impacts which insects and diseases were to have upon seed production within these orchards and consequently upon the regeneration efforts across the South was not fully realized until Weir (1975) reported that the loss of seed from seed orchard insects would have a larger impact on the forest economy than the current losses from the southern pine beetle, one of the most destructive pests in the region. During the Twelfth Southern Forest Tree Improvement Conference a questionnaire concerning seed orchard problems and priorities was circulated and respondents indicated that cone and seed insect control was their most pressing concern. These respondents stressed that research should be expanded to (1) develop procedures to efficiently monitor insect impact in seed or­ chards, (2) screen available and new insecticides and to test application methods, (3) submit effective insecticides for registration, and (4) establish biological and behavioral studies involving both pests and their predators. If we polled an similar group of tree improvement specialists about their current management problems and concerns I'm sure we would arrive at a similar list of concerns. If the problems and concerns have remained the same, does that mean that we have made very little progress in attempting to solve these problems. Actually seed orchard pest management strategies are rapidly evolving and several dramatic changes have occurred in the last 10 years.

First Generation Pest Management Strategies — 1955-1970

First generation pest management strategies implemented on southern pine seed orchards consisted of insecticide applications applied to control indirect pests, insects which feed on vegetative structures, and active sanitation practices for suppression of fusiform rust, pitch canker and secondary insect pests such as IPs engraver beetles and deodar weevils. During the early 1960's orchard managers treated their newly grafted trees with chemicals such as BHC, DDT, heptachlor, and azinphosmethyl (Guthion ). Chemical treatments were applied using high volume hydraulic sprayers or low volume airblast sprayers. Because the trees were small, good coverage was assured.

Second Generation Pest Management Strategies — 1970-1980

Second generation pest management strategies began in the 1970's and lasted until the early 1980's. During this period. The Seed Orchard Pest Committee (S-118); consisting of members from USDA - Forest Service, university research, each of the southern forest tree improvement cooperatives, and states without membership in the cooperatives, was formed to spearhead pest management efforts. This committee coordinated pesticide testing efforts particularly the

16 activities resulting in registration of carbofuran (Furadan ) in granular formulation for use on southern pine seed orchards.

Key pests attacking the major species of southern pines were identified and existing information on their biologies was compiled. Life history and impact studies were Installed across the South. In 1974, Yates compiled a list of the potential insect pests which were considered as having significant impact. Of the species mentioned, adequate biological information was avail­ able for 17 percent, basic biology for 44 percent, and little or no biology for 39 percent. Publication of the Seed and Cone Insects of Southern Pines in 1975 gave the seed orchard managers their first field guide to pest identification and biology. A revision of this technical report was published in 1980 and except for a few taxonomic changes for some of the major coneworm species and the addition of the southern cone gall midge the publication remains similar to the first edition.

By the 1970’s many of the orchards were in full production. Demand for seed was high and losses due to insect pests were not acceptable. Without techniques to detect and monitor these pests adequate protection could only be assured by maintaining lethal pesticide residues throughout the summer. Many of the more persistant pesticides were withdrawn from the market and orchard managers were forced to rely upon pest management strategies featuring a February application of carbofuran and monthly applications of less persistant pesticides such as azinphosmethyl. Results were not always satisfactory. Several reasons for these failures were postulated. Spray coverage from hydraulic and airblast sprayers on trees over 50 feet tall was not adequate, particularly in the upper half of the tree crown where 76 - 87 percent of the cones are located (DeBarr, et al. 1975). Composite life histories of the 7-10 key pests indicated that damaging stages of one species of another may be present throughout the summer, and therefore, timing for maximum effectiveness without prior knowledge of pest complexes accurate timing of applications was impossible on large orchards where a full coverage ground spray may take three weeks. These problems prompted the development of third generation pest management strategies.

Third Generation Pest Management Strategies — 1980-Present

Current pest management strategies are gradually moving away from the generalized monthly spray schedule. Individual orchard strategies will be developed which will reflect current conditions. In order to develop these strategies considerable research is needed in the following areas —— pest biologies, alternative insecticides, application methods, pest monitoring techniques, and application timing methods.

Pest Biologies

More recent biological investigations have clarified or filled in existing gaps in our knowledge of pest biologies. The 1979—80 population outbreak of the webbing coneworm (Dioryctria disclusa) throughout the southern Atlantic states provided researchers with an opportunity to document larval feeding in male catkins followed by migration to second year cones as the male catkins dried and fell from the trees. This migration usually occurs within a seven day period after peak pollen flight. Based upon these findings orchard 17 managers who had experienced losses caused by the webbing coneworm were encour­ aged to apply a pesticide during this "window of opportunity" - seven days post pollen flight (DeBarr, et al. 1982). While localized population outbreaks have occurred at several orchards east of the Mississippi River; no serious out­ breaks have been recorded in Louisiana, Texas, or Arkansas. The significance of the geographical distribution of these outbreaks is not known.

The southern pine coneworm (D. amatella) has been described routinely as the most damaging multivoltine coneworm species, but confusion exists concern­ ing the number of generations and the synchrony of these generations. Recent research by Hanula, et al. (in press) suggests "that most of the HI amatella population in Georgia has two generations per year". Overwintering larvae found within fusiform galls or other wounds on the bole pupate in the spring and adults emerge in May or June. The progeny of the first generation attack second year cones where they mature, pupate, and emerge in September or Octo­ ber. Hanula, et al. (in press) found a small portion of the population which was out of synchrony with the rest of the population. These individuals emerge in July resulting in low levels of adult activity throughout the summer. Other researchers have documented similar adult flight peaks in other states throughout the range (Merkel and Fatziner 1975, Florida; Chatelain and Goyer 1980, Louisiana; Tauer, et al. 1983, Oklahoma).

Several indirect pests l^ve appeared across the South in orchards which have used fenvalerate (Pydrin ) as an alternative chemical to azinphosmethyl. Four scales, the striped pine scale, (Tourneyella pini), the pine tortoise scale, (T. parvicomis), the woolly pine scale, (Pseudophilippia quaintancii), and the pine needle scale (Chinonaspis heterophyllae), have occurred in mixed populations and in several cases outbreaks have been responsible for reduced flower production (Barber and Leonard 1982), reduced annual growth increments (communications with L.R. Barber) and even tree mortality (communications with L.R. Barber). Cameron (1984) reported that "the two Toumeyella scales appear to have more than one generation per year and that crawlers (first stage immatures) of one or the other species were present at nearly all time from March through October." Additional work on the biologies of these scale complexes is needed, particularly as it relates to our current pest management strategies.

Outbreaks of two other indirect pests, a mealybug (Oracella acuta) and a loblolly pine needle sheath midge (Contarinia n. sp.) have occurred at several scattered orchards. Evidence indicates that outbreaks of both of these pests may be in response to low volume aerial applications of Insecticide.

Research continues into the biologies of seed orchard pests. Unfortunate­ ly funding for this type of research has been drastically reduced.

Alternative Insecticides

The need for alternative chemicals for use on southern pine seed orchards has been a recurring theme in the search for effective pest management stra­ tegies. Fortunately insect resistance to the standard insecticide, azinphosmethyl, has not occurred and may never be a problem because of continu­ ous pest immigration from the surrounding stands. However the locations of many orchards prevent the use of chemicals with high mammalian toxicity

18 (azinphosmethyl) or chemicals which are highly mobile in sandy soils (carbofuran).

In 1978, many orchard managers reported inconsistant insect control with carbofuran and by 1981 many orchards had returned to more traditional ground applications of liquid insecticides. During this period high volume and low volume applications of fenvalerate, permethrin (Ambush ), and phosmet (Imidan ) were evaluated for effectiveness against coneworms and seed bugs. "Mistblower applications of fenvalerate and permethrin repeated five or six times at monthly intervals compared favorably with azinphosmethyl for coneworm control in South Carolina but were less effective in Louisiana (Nord, et al. 1985). Both fenvalerate and permethrin effectively reduced seed bug damage. As a result of these studies the Forest Service submitted the necessary efficacy data and fenvalerate and permethrin were registered. Efficacy data for phosmet have been submitted to the company but registration has not been completed.

Fenvalerate and permethrin, both synthetic pyrethroids, were new classes of insecticides and their beneficial characteristics, low mammalian toxicity and long residuals, mad ethem extremely appealing chemicals for use on seed or­ chards. Due to a restriction on the azinphosmethyl label which required applications to be at least 30 days apart, many orchard managers began supple­ menting monthly azinphosmethyl applications with applications of fenvalerate. Coneworm and seed bug control was enhanced but unfortunately even one spring application of fenvalerate released population outbreaks of the four scale species described in the pest biologies section of this paper. Apparently these synthetic pyrethroids effectively reduce predator and parasite popu­ lations without reducing scale populations. These scale outbreaks have reached damaging levels resulting in the elimination of fenvalerate from the effective chemical arsenal. By re-evaluating these synthetic pyrethroids, an effective rate and pattern of use may be determined and these chemicals might be extreme­ ly useful in future pest management strategies. R Acephate (Orthene ) which is already labelled for use on southern pines is being tested in Florida for control of thrips, coneworms, and seed bugs (com­ munications with C.W.^ Fatzinger). Implants „ of systemics insecticides (Dicrotophos - Bidrin , dim^hoate - Cygon , carbofuran - Furadan , oxydemeton-methyl - Metasystox-R , and acephate - Orthene ) have been evaluated for use against cone and seed pests. "Significant reductions in cone damage caused by coneworms and seed losses caused by seed bugs occurred on trees protected with a single annual application of dicrotophos, oxydemeton-methyl, or acephate implanted into drill holes on April 1, 1982 (DeBarr, et al. in press). This method of control might be useful for protection of control pollinated crosses, designated high value trees, or in environmentally sensitive orchards. Mistblower applications of dormant oil with and without Ethion are being tested as late dormancy treatments for control of scale outbreaks.

In spite of these insecticide studies, the seed orchard manager still must rely primarily on azinphosmethyl. The azinphosmethyl label has been amended in order to increase the flexibility of timed sprays. Applications may be made more frequently than 30 days apart as long as lesser concentrations are ap­ plied. In addition, the first spring application has been advanced to within one week of peak pollen flight. Research has shown that flower survival is not effected by early azinphosmethyl applications.

19 Application Methods

Accurate and adequate coverage of young trees with liquid insecticide applied by traditional ground equipment is possible. However as trees exceed the 50 foot height less than desirable coverage on cones, conelets, and foliage is common. In 1980 a pilot project was initiated to compare and evaluate spray deposition on seed orchard trees resulting from both aerial and ground applica­ tions and to develop a strategy for aerial application of pesticides which maximizes spray deposition to targets and minimizes drift (Barry, et al. 1982). This project demonstrated that ground sprayers can achieve spray coverage equal to or greater than that of fixed-wing or helicopter applications on trees less than 50 feet tall. Helicopter applications deposited approximately 70 percent more spray within the upper canopy as opposed to fixed-wing applications. The results also indicated that "minimal but detectable spray drift from aerial applications can be expected to occur 133 meters downwind depending upon wind speed, wind direction, and other atmospheric conditions" (Barry et al. 1984). After the completion of this project, two pilot projects were initiated to demonstrate the effectiveness of aerial applications of azinphosmethyl and fenvalerate for coneworm and seed bug suppression. Conelet and cone survival was significantly better in the treatment blocks as compared to the untreated block (Weatherby and Overgaard 1983). Shortly after the completion of these projects, the azinphosmethyl and fenvalerate labels were ammended to permit aerial applications. These aerial application initiatives resulted in a shift away from soil incorporation of carbofuran and ground applications of liquid insecticides to aerial applications. By 1982, 44 percent of 34 orchards surveyed were applying insecticides by aircraft (Barber 1984).

There is a real need for additional aerial application research. Speci­ fications for aerial applications developed after these pilot projects recom­ mended droplet sizes of 300-350 microns (VMD) and two pass applications of five gallons per acre per pass. Preliminary information concerning ultra low volume or low volume applications in forestry situations indicates that coverage and canopy penetration may be improved with these types of applications. A prelim­ inary evaluation of one pass versus two pass applications of the same amount of active ingredient suggests that both methods provide protection of cones from coneworm damage. Conelet survival data are inconclusive.

Pest Monitoring Techniques

Synthetic sex pheromones "are available for almost a dozen different species of seed and cone insects" including the four major coneworm species (DeBarr and Berisford 1984). During the last four years more than 60 orchards across the South have participated in the coneworm pheromone survey as a part of their pest management programs. Orchard managers are using the pheromone trapping program to detect the presence of damaging species and to establish relative yearly population trends. Currently the survey includes baits which will capture four coneworm species - D. clarioralis, D. disclusa, D. merkeli, and I), amatella. "It has been demonstrated that these inexpensive traps provide a highly specific detection technique that can be used by trained seed orchard managers as an early warning system to alert orchard personnel to possible needs for preventative action" (De Barr and Berisford 1984).

Pheromone traps for the Nantucket pine tip moth (Rhyacionia frustrana) have been used to provide a site specific biofix for timed pesticide applica­

20 tions (Gariullo, et al. 1983). Studies are currently in progress to develop similar systems for timing insecticide applications for the major coneworm species. As these types of systems are developed pheromone trapping will become an integral part of the seed orchard pest management program.

One area of pest management which has developed from the use of pheromones for trapping purposes is the use of pheromones as a control method through mating disruption. Releases of synthetic attractants compete with the natural communication system and males are unable to locate mates. Three preliminary studies in pheromone mediated mating disruption have been attempted but the results have been inconclusive. Additional research is needed to determined if this technique will be successful for seed orchard pests.

Method of Timing Insecticide Applications

IPM systems used in other agroeconomic crops have relied upon temperature accumulations to predict pest phenologies. These developmental models have increased the effectiveness of sprays which are timed to coincide with the appearance of susceptible life stages. The Nantucket pine tip moth model developed by Gargiullo, et al. (1983) is a day-degree model which has been used successfully in Christmas tree plantations and in seed orchards. The beginning of each generation is established when the first tip moth is caught in pheromone traps. Day-degrees are accumulated until the sum indicates that first and second instar larvae of the subsequent generation are present. The following day is the optimum spray date.

A few orchard managers are beginning to monitor both temperature accumula­ tions and coneworm pheromone traps. After several seasons of data collection to onset or peaks of the adult flights can be converted to generalized day- degree scales. These day-degree models can be used in subsequent seasons to predict the date of moth emergence. In the future, day-degree models will be available for the major pests. Applications will be timed based upon the on-site temperature accumulations for each orchard.

Conclusions

Many new pest management techniques are available for use on southern pine seed orchards. Integrating these new techniques and methods into a functioning pest management system is a challenging task. In the future seed orchard managers will detect key pests with monitoring techniques such as pheromone trapping. Temperature driven developmental models will predict when damaging life stages of these pests should be treated. Updated predictions will "pin point" the most "effective times to apply insecticides. Pesticides will be applied aerially or by other timely methods. These third generation pest management strategies will abandon the typical calender spray schedule relying instead upon flexible schedules which are specific and responsive to pest problems found on each orchard.

21 Literature Cited

Barber, L.R., and D.S. Leonard. 1982. An evaluation of conelet populations on trees treated two years with Pydrin or Guthion, Weyerhauser Seed Orchard, Washington, N.C. 1982, USDA-FS, R-8. Field Office Rep. #82-1-31. 7 p.

Barber, L.R. 1984. Insecticide application methods for southern pine seed orchards. Proc. of the Cone and Seed Insects Working Party Conference S2.07-01. Southeastern For. Exp. Stn. Pub.:130-136.

Barry, J.W., P.A. Kenney, L.R. Barber, R.B. Edbald, R.J. Dumbauld, J.E. Rafferty, H.W. Flake, and N.A. Overgaard. 1982. Aerial application to southern pine seed orchards: Data report of the Withlacoochee Trials. USDA-FS, R-8. Field Office Report #82-1-23. 99 p.

Barry, J.W., L.R. Barber, D.A. Kenney, and N.A. Overgaard. 1984. Feasibility of aerial spraying of southern pine seed orchards. So. Jor. Appl. For. 8(3):127-131.

Cameron, R.S. 1984. Scale insects in pine seed orchards. Texas Forest Pest Report 1982-1983. Texas For. Ser. Pub. #136:14-16.

Chatelain, M.P. and R.A. Goyer. 1980. Seasonal attack periods of cone-feeding insects of loblolly pine cones. Ann. Entomol. Soc. Am. 73:49-53.

DeBarr, G.L., L.R. Barber, and R.C. Wilkinson. 1975. Within-crown distribu­ tion of cones and seed insect damage to slash pine flowers, conelets, and cones. Fla. Entomol. 58:281-288.

DeBarr, G.L., L.R. Barber, C.W. Berisford, and J.C. Weatherby. 1982. Pheromone traps detect webbing coneworms in loblolly pine seed orchards. So. Jour. Appl. For. 6(2):122-127.

DeBarr, G.L., C.W. Berisford. 1984. Use of sex pheromones for seed and cone insect pest management in conifer seed orchards. Proc. of the Cone and Seed Insects Working Party Conference. S2.07-01. Southeastern For. Exp. Stn. Pub.:194-203.

DeBarr, G.L., A.L. Platt, and J. Wright. Implanted systemic insecticides for control of seed of and cone insects and loblolly pine, (in press).

Gargiullo, P.M., C.W. Berisford, C.G. Canalos, and J.A. Richmond. 1983. How to time dimethoate sprays against the Nantucket pine tip moth. Ga. For. Research Paper 44. 10 p.

Hanual, J.L., G.L. DeBarr, and C.W. Berisford. Comparison of pheromone and blacklight trap catches of the adult Dioryctria amatella (Lepidoptera: Pyralidae) with immature development in loblolly pine cones. Environ. Entomol. (in press).

Merkel, E.P. and C.W. Fatzinger. 1971. Periodic abundance of pine cone- infesting Lepidoptera in blacklight traps and sleeve cages in north Florida. Fla. Entomol. 54:53-61.

22 Nord, J.C., G.L. DeBarr, L.R. Barber, J.C. Weatherby, and N.A. Overgaard. 1985. Low-volume applications of azinphosmethyl, fenvalerate, and permethrin for control of coneworms (Lepidoptera: Pyralidae) and seed bugs (Hemiptera: Coreidae and Pentatomidae) in southern pine seed orchards. Gcon. Entomol. (in press).

Tauer, C.G., R.D. Eikenberry, and G.M. LeHar. 1983. Light trapping cone and seed insects (Lepidoptera: Tortricidae and Pyralidae) of pine in south­ eastern Oklahoma. Environ. Entomol. 12:753-757.

Weatherby, J.C., and N.A. Overgaard. 1983. Final Report: Pilot test for controlling coneworms and seed bugs by aerial application of Pydrin and Guthion at the Beauregard State Seed Orchard, DeRidder, La. USDA-FS, R08. Field Office Report #83-2-12. 16 p.

Weir, R.J. 1975. Cone and seed insects - southern pine beetle: A contrasting impact on forest productivity. Proc. 13th South. For. Tree Improv. Conf., Raleigh, N.C.:182-192.

23 NURSERY DISEASES - OUTPLANTING SURVIVAL AS AFFECTED BY SEEDLING QUALITY

S.J. Rowan Principal plant pathologist USDA Forest Service Forestry Sciences Laboratory Athens, GA 30602

Forest land managers are becoming more aware of the financial impact of regeneration practices on the yield of plantations of southern pines. Planta­ tions established on unprepared or poorly prepared sites may have significant numbers of planting spaces that were never planted. The number of such spaces (missed) increases with roughness of the terrain, planting crews, and planting machinery. Certain planting crews— regardless of planting method— and certain planting machines— regardless of planting crew— improperly plant seedlings in rough terrain, resulting in substantial mortality rates. Initial stocking is important to the final yield of a plantation and careful supervision of crews that that prepare sites and outplant seedlings can add significant profit to each rotation crop (Table 1; Godbee et al. 1983).

Table 1. Effect of regeneration costs on production cost per cord of wood.

Regeneration Stems/acre Volume/acre Future cost cost/acre at age 25 at age 25 per cord (dollars) (No.) (cords) at 10% interest

90 300 27.9 $34.95

90 400 34.4 28.35

90 500 39.8 24.50

Poor seedling quality (size, disease incidence, genotype, physiology, etc.) is often pointed to in explanation for poor growth and survival of plantations but little information is available correlating measures of quality and performance. Godbee et al. (1983) indicated that improper planting accounted for the majority of mortality in Union-Camp Corporation plantings. The work reported in this paper was begun in 1979 in an attempt to determine if the rates of survival and growth of seedlings differed among the nine Georgia nurseries, differed by methods of lifting, by methods of transportation, handling and planting by landowners, lifting and planting dates, and by out- planting sites.

Rate of seedling survival obtained by the average landowner was determined among 49 random landowners in 1979-1980 (Table 2) and among 35 random landown­ ers in 1980-1981 (Table 3). Survival ranged from 0 to 89 percent

24 Table 2. First-year survival of pine seedlings produced in Georgia Forestry Commission nurseries and planted by landowners or contractors on 49 random sites in 46 Georgia counties during 1979-1980 planting season.

County Percent County Percent

Appling 46.2 Morgan 5.0 Baldwin 60.7 Muscogee 79.0 Bartow 82.0 Putnam 79.7 Brantley 53.0 Randolph 62.0 Bulloch 55.0 Richmond 70.4 Burke 17.3 Schley 76.9 Butts 77.3 Screven 68.0 Clarke 62.0 Stewart 91.1 Clayton 54.0 Sumter 30.4 Columbia 0.0 Talbot 77.3 Coweta 77.0 Taliaferro 71.6 Dooly 71.0 Tattnall 58.9 Emanuel 67.0 Taylor 78.3 Evans 56.5 Toombs 37.0 Fayette 76.0 Twiggs 28.8 Glascock 88.6 Warren 6.0 Gordon 76.0 Warren 68.3 Hancock 88.5 Washington 16.0 Harris 81.9 Washington 66.0 Jeff Davis 86.2 Washington 0.0 Jefferson 42.0 Wayne 87.3 Jenkins 69.0 Webster 74.9 Johnson 71.0 Wilkes 47.0 Lincoln 44.5 Wilkinson 0.0 Macon 0.0

25 Table 3. First-year survival of pine seedlings produced in Georgia Forestry Commission nurseries and planted by landowners or contractors on 35 random sites in 30 Georgia counties during 1980-1981 planting season.

County Percent County Percent

Baker 53.4 Irwin 59.5 Baldwin 77.0 Madison 39.9 Ben Hill 73.0 Mitchell 73.9 Brooks 65.7 Oconee 46.3 Calhoun 43.5 Oglethorpe 37.8 Chattooga 99.0 Paulding 49.0 Chattooga 75.0 Paulding 39.0 Clay 28.2 Polk 47.0 Clinch 66.0 Polk 40.0 Colquitt 60.3 Pierce 54.0 Cowetta 86.7 Seminole 68.0 Decatur 95.0 Tift 91.8 Early 90.0 Walker 68.0 Elbert 65.9 Walton 85.9 Grady 71.0 Warren 27.0 Greene 38.5 Worth 88.1 Haralson 31.0 Worth 52.4 Haralson 95.0

(average 60%) in 1979-1980 plantings and ranged from 27 to 99 percent (average 62%) in 1980-1981 illustrating large variation in rates of survival of seedlings from Georgia Forestry Commission nurseries.

Method of lifting was shown to significantly affect rates of survival (Tables 4 and 5) but lifting seedlings with tender loving care only improved survival by 11.0% in 1979-1980 and 6.1% in 1980-1981 (average 8.6%). Method of transport affected the rate of survival in only 1 of 2 years (Tables 4 and 5) and the average improvement for the 2 years was 4.1% if extra care was taken during transport of seedlings from nursery to planting site.

Although seedlings from the nine Georgia nurseries differed in size, weight, disease incidence, and other measurements at lifting, their rates of survival did not differ significantly due to nursery source (Tables 6, 7, and 8). Outplanting site did significantly affect rates of survival (Tables 6 and 7).

Although lifting seedlings with tender loving care was shown to improve survival by 8.6 percent during the 2-year period (Tables 4 and 5), only 2,200 TLC seedlings were outplanted. Survival was also shown to be improved by TLC lifting among seedlings lifted from all Georgia nurseries and outplanted on five sites during a 2-year period (Table 9). The average improvement due to TLC lifting was 7.3 percent among these 25,200 outplanted seedlings.

26 Table 4. First—year survival of pine seedlings produced in Georgia Forestry Commission nurseries lifted opera­ tionally by nursery personnel (Reg) and by the author with tender loving care (TLC), transported to the landowner by state truck delivery (State) and by the author (Hand), and outplanted on the landowner's site by landowner (LO) or by the author in randomized complete block design during 1979-1980.

Site Site Site Site Site Site Lift Transport 1 2 3 4 5 6 method method (Morgan) (Warren) (Clarke) (Washington) (Washinton) (Brantley) Avg.

Percent Reg Hand 85.0 a 12.1 b 62.6 b 82.1 b 1.0 a 82.0 b 54.1 Reg State 74.0 b 11.2 b 57.5 b 83.0 b 0.0 a 51.0 c 46.1 a 2 7 TLC Hand 83.0 a 24.0 a 76.3 a 92.7 a 0.0 a 99.0 a 62.5 TLC State 82.0 a 28.6 a 64.0 b 92.0 a 1.0 a 91.2 a 59.8 Reg State (LO) 5.0 c 6.0 b 62.0 b 66.0 c 0.0 a 53.0 c 32.0 b

Avg Reg lift 79.5 a 11.6 b 60.0 b 82.5 a 0.5 a 66.5 b 50.1 b Avg TLC lift 82.5 a 26.3 a 70.1 a 92.3 a 0.5 a 95.1 a 61.1 a

Avg Hand transport 84.0 a 18.0 a 69.4 a 87.4 a 0.5 a 90.5 a 58.3 a Avg State transport 78.0 a 19.9 a 60.7 b 87.5 a 0.5 a 71.1 b 52.9 b

Column means followed by a common letter do not differ significantly (P=0.05) according to Duncan's multiple range test. Paired mean averages should not be compared with other means. Table 5. First-year survival of pine seedlings produced in Georgia Forestry Commission nurseries lifted opera­ tionally by nursery personnel (Reg) and by the author with tender loving care (TLC), transported to the landowner by state truck delivery (State) and by the author (Hand), and outplanted on the landowner's site by landowner (LO) or by the author in randomized complete block design during 1980-1981.

Site Site Site Site Site Lift Transport 1 2 3 4 5 method method (Baldwin) (Warren) (Greene) (Clinch) (Pierce) Avg.

■Percent

Reg Hand 99.1 a 98.0 a 93.2 a 84.0 b 88.0 c 92.5 Reg State 98.0 a 97.0 a 74.2 a 88.0 b 79.0 d 87.2 a TLC Hand 95.0 a 95.0 a 93.0 a 98.0 a 100.0 a 96.2 TLC State 99.1 a 99.0 a 92.1 a 97.0 a 91.2 b 95.7 Reg State (LO) 77.0 b 27.0 b 38.5 b 66.0 c 54.0 e 52.5 b

Avg Reg lift 98.6 a 97.5 a 83.7 a 86.0 b 83.5 b 89.9 b Avg TLC lift 97.1 a 97.0 a 92.6 a 97.5 a 95.6 a 96.0 a

Avg Hand transport 97.1 a 96.5 a 93.1 a 91.0 a 94.0 a 94.3 a Avg State transport 98.6 a 98.0a 83.2a 92.5 a 85.1 b 91.5 a

Column means followed by a common letter do not differ significantly (P=0.05) according to Duncan's multiple range test. Paired mean averages should not be compared with other means. Table 6. First-year survival of loblolly pine seedlings lifted from each nursery in Georgia and outplanted on each of three sites during 1979-1980 planting season.

N ursery source Oglethorpe Baldwin Ware Average

P ercen t

Morgan 6 4 .6 37.5 92.7 6 4 .9 a

Page-Walker 5 5 .2 38.5 95.8 63.2 a

H iw assee 39.2 39.1 92.1 56.8 a

Great Southern 5 8 .2 37.8 96.2 64.1 a

Cont. For. Ind. 49 .9 29.4 91.0 56.8 a

Union-Camp 6 4 .6 30.0 92.2 62.3 a

R ayonier 57.1 26.2 93.7 59.0 a

Brunswick P&P 4 8 .4 34.2 94.6 59.1 a

Ave. 54.7 B 34.1 A 93.5 C

Column means followed by a common lowercase letter or row means followed by a common uppercase letter do not differ significantly (P=0.05) according to Duncan's multiple range test.

29 Table 7. First-year survival of loblolly pine seedlings lifted from each nursery in Georgia and outplanted on each of two sites during 1980- 1981 planting season.

Nursery source Baldwin Ware Average

Morgan 71.5 ab 88.8 b 80.1 be

Page-Walker 73.1 b 88.6 ab 80.9 c

Hiwassee 62.4 a 86.0 ab 74.2 abc

Great Southern 65.7 ab 82.9 ab 74.3 abc

Cont. For. Ind. 62.1 a 84.5 ab 73.3 ab

Union-Camp 67.4 ab 91.9 b 79.7 be

Rayonier 65.1 ab 83.2ab 74.2abc

Brunswick P&P 62.1 a 79.0 a 70.5 a

Ga. Kraft 66.5 a 90.0 b 78.3 be

Ave. 66.2 A 86.1 B

Column means followed by a common lowercase letter or row means followed by a common uppercase letter do not differ significantly (P=0.05) according to Duncan's multiple range test.

30 Table 8. First-year survival of loblolly pine seedlings lifted from each nursery in Georgia and outplanted during 1981-1982 planting season.

Nursery Survival source (%)

Morgan 95.3 a

Page-Walker 98.5 a

Hiwassee 98.6 a

Great Southern 97.5 a

Cont. For. Ind. 97.8 a

Union-Camp 99.3 a

Rayonier 98.3 a

Brunswick 98.4 a

Ga. Kraft 98.8 a

Means followed by a common letter do not differ significantly (P=0.05) accord­ ing to Duncan's multiple range test.

31 Outplanting date also affected survival on some but not all sites in each of 2 years (Table 9). The greatest improvement in rate of survival resulted from extra care during outplanting on 11 random Georgia sites (Tables 4 and 5). Survival was improved by 14 percent in 1979-1980 and by 35 percent in 1980-1981— an average of 24 percent improvement for both years (Tables 4 and 5).

It can, therefore, be concluded that some improvement in seedling quality can be realized from greater care during transport of seedlings from nursery to outplanting site and during lifting of seedlings from nursery beds, but care during transplanting by outplanting crews can provide more improvement in seedling survival than can improved transportation and lifting methods. Disease incidence (Fusiform rust, root rot) and other differences in seedling quality (71 measured variables) among seedlings lifted from nine Georgia nurseries during the 3 years of this study did not cause survival rates to differ significantly among nurseries. Top/root ratio was the best predictor of survival and those seedlings that survived best also grew best. Weight of large roots was more important to seedling growth than was the weight of small roots (including feeder roots). Larger lateral and feeder roots were more important to seedling survival than were smaller feeder roots.

Summary

Survival and growth of loblolly pine seedlings from nine Georgia nurseries were monitored in several plantations established during 3 consecutive years. Outplanted seedlings were lifted both operationally and with tender loving care (TLC). Rates of survival and growth were correlated with 71 X-variables generated from seedling measurements made at lifting. Incidence of fusiform rust, root rot severity, root and shoot biomass, and other variables were included among the measurements. Poor handling and poor planting techniques by landowners or planting contractors caused more mortality than all other measured causes. Shoot-root ratio was the best predictor of increased survival and improved survival, was correlated with increased growth.

Literature Cited

Goddbee, J.F., Jr., J.L. Rakestraw, and F.S. Broeman. 1983. Pine plantation survival: A corporate look at the problem. Proc. 1982 Southern Nursery Conf. USDA For. Serv. Tech. Publ. R8TP4:21-26. Savannah, GA.

32 Table 9. First-year survival of loblolly pine seedlings lifted operationally (Reg) by nursery personnel and with tender loving care (TLC) by the author and outplanted during January, February, and March on three sites in 1979-1980 and on two sites in 1980-1981.

Oglethorpe Baldwin Ware Average

1979-1980 lifting

Reg. 50.9 a 32.2 a 91.5 a 58.0 a TLC 58.5 b 35.9 a 95.6 b 63.3 b

1980-1981 lifting

Reg. — 62.0 a 81.1 a 71.6 a TLC 70.5 b 91.1 b 80.8 b

1979-1980 lifting

Jan. 44.2 a 31.9 a 87.7 a 54.6 a Feb. 58.1 b 29.3 a 96.2 a 61.2 a Mar. 61.7 c 41.0 b 96.7 a 66.5 a

1980-1981 lifting

Jan. — 63.6 a 90.6 b 77.1 b Feb. - 72.0 b 87.2 b 79.6 b Mar. 63.0 a 80.6 a 71.8 a

Column means within each year and lifting method or planting date followed by a common letter do not differ significantly (P=0.05) according to Duncan's multiple range test.

33 SESSION II

Moderator:

Mr. Michael P. Mety State Forester Louisiana Office of Forestry Baton Rouge, LA

34 A DECISION SUPPORT SYSTEM FOR THE SOUTHERN PINE BEETLE

Robert N. Coulson Department of Entomology Texas A&M University

Michael C. Saunders Formerly Department of Entomology Texas A&M University Currently Assistant Professor Department of Entomology Pennsylvania State University

Koushen D . Loh Department of Range Science Texas A&M University

Edward J. Rykiel Department of Industrial Engineering Texas A&M University

Thomas L. Payne and Paul E. Pulley Department of Entomology Texas A&M University

Lorinda C. Hu^ Department of Industrial Engineering Texas A&M University

During the last decade the knowledge base for the southern pine beetle, Dendroctonus frontalis Zimmermann, was greatly expanded. This circumstance occurred because of accelerated research and development programs conducted throughout the Southern region. The goal for this research effort was to develop an integrated pest management (IPM) system for the insect. Published literature on the subject has been reviewed and summarized in Thatcher et al. (1980), Kulhavy and Johnson (1983), and Payne et al. (1984).

Traditional methods for technology transfer were not adequate for deliver­ ing the full measure of knowledge available to the forestry user community. This circumstance led to an examination of methodologies for computer-aided decision making and information accessing (Rykiel et al. 1984). One type of system, which is particularly applicable to complex problems in IPM, is the decision support system (DSS). A DSS is a computer-based system designed to help decision makers utilize data and models to solve unstructured problems (Sprague 1980). Problem structure refers to the degree to which a solution to a problem can be specific in advance (Keen and Morton 1978).

The Texas Agricultural Experiment Station and The Texas Engineering Experiment Station developed a DSS for the D. frontalis knowledge base. The

Texas Agricultural Experiment Station Paper ______.

35 goal of this paper is to report on this system. Our specific objectives are (1) to review the issues that created the need for computer-aided decision making, (2) to describe the characteristics and structure of the southern pine beetle decision support system, (3) to discuss implementation of the system, and (4) to identify future worthwhile developments for the system.

Conditions that Created the Need for Computer-Aided Decision Making

During the years between 1970 and 1985 there were three accelerated research and development programs conducted on D. frontalis: the Huffaker NSF Pines - Bark Beetle Project (Waters et al. 1985), the Expanded Southern Pine Beetle Research and Applications Program (ESPBRAP), and the USDA IPM Program. This organized and directed research effort, which was unprecedented in forest protection research in the South, resulted in a rapid and significant expansion of the knowledge base on D. frontalis. Many of the research projects consisted of interdisciplinary teams of scientists from a variety of academic special­ ties. The mathematical modeling methodology was used to abstract research results. Therefore, the knowledge base consists of both mathematical models as well as technical information. Ca 35 models are currently available that deal with population dynamics of D. frontalis, stand growth and yield, stand hazard rating, stand risk rating, and economics. Furthermore, there are ca 2000 published papers dealing with D. frontalis.

Because of the size and complexity of the knowledge base (models and technical information) on IK frontalis, it could not be effectively utilized in IPM decision making. One solution to this problem was the development of a computer-based decision support system.

Characteristics and Structure of the

Southern Pine Beetle Decision Support System (SPBDSS)

Characteristics of SPBDSS

The Southern Pine Beetle Decision Support System (SPBDSS) was built with the understanding that the end users have little time to deal with an inflexi­ ble computing system. Neither could the end users be expected to have more than a casual familiarity with all of the knowledge that is available to solve their problems. The function of SPBDSS is to provide access to the knowledge base (models and technical information) relevant to forest management problems associated with D^. frontalis. The system was built on the premise that better decisions can be made when forest managers have the capability to review all existing information about particular problems and potential solutions.

SPBDSS is a large and complex FORTRAN computer code. Because of its interactive format, the size and complexity are transparent to the user. The system was developed for a mainframe computer and it is accessed through remote terminals or microcomputers. Since the knowledge base for D. frontalis is dynamic, the computer code was developed in a modular format, which permits additions and modifications to the system as needed.

36 SPBDSS differs from conventional data processing systems in four important ways. First, the focus of the system is on decision making in problem situa­ tions rather than simply information retrieval, processing, or reporting. Second, the system is intended to be an integral part of the user's decision process relative to problems dealing with the influence of D. frontalis on forest management practices. Third, the procedures for using the system are "loosely defined" rather than pre-specified. Fourth, the purpose of the system is to improve the effectiveness of decision making rather than enhancing efficiency of information retrieval.

The general function of SPBDSS is as follows. The user enters a question (problem) on a terminal or a microcomputer. This question is examined through a problem analysis routine called FERRET (Turnbow et al. 1983). The exact nature of the problem is defined by response of the user to a series of prompts and menus. This step is important because it helps to clarify specifically what the user wishes to know and it guides the user to the available models and technical information relative to the problem. The pertinent entries in the knowledge base are displayed to the user along with the option to examine them. If the problem only involves technical information, the user can review the entries and/or obtain a printed copy. However, if the problem involves use of the model base, the system will identify needed models, allow examination of input requirements and output, sequence the models, request input values, conduct the simulations(s), and print a report. Some problems may involve technical information and models and a final report can contain both. Further­ more, once a problem has been investigated, a course of action may be identi­ fied which requires further use of the knowledge base for D frontalis. For example, a user's first question might be, "I have a 15—tree infestation in a stand; will it increase in size during the next 90 days?" If the answer to this question were yes and it will contain 500 trees, the next logical question would likely be, "What are my options for suppression of beetle populations?" SPBDSS has an option termed "problem migration" by which the user can move directly to the needed information without returning to the beginning of problem analysis.

There are several additional features of SPBDSS. There is a help rou­ tine" which provides a tutorial on the use of the system and a glossary of technical terms. The system contains a user file system for storage and retrieval of simulation results. This option can save results of multiple simulations and also eliminates the need to re-enter data used to initiate simulations. Additional options are described in Saunders et al. (1985).

Structure of SPBDSS

The structure and operation of SPBDSS have been described in detail by Loh (1984), Rykiel et al. (1984), Saunders et al. (1985a & b)? Here we will simply examine the basic components that comprise the system, which are illustrated in Figure 1. The fundamental components include (1) model base, (2) data base, (3) model base management system, (4) data base management system, (5) problem analysis program, (6) control program (executive routine), and (7) dialogue generation and management system.

Model Base.— The model base currently holds 31 models that deal with population dynamics, stand growth and yield, stand hazard rating, stand risk rating, and economics. The entire model base can be accessed and executed in

37 Figure 1.

38 batch format by knowledgeable users. This archive provides a centralized location for models dealing with I), frontalis IPM. However, batch format execution of models is not the primary aim of SPBDSS, which is interactive problem solving. Accordingly, 13 models, judged to be particularly relevant to IPM decision making, were selected, translated into a common language (FORTRAN IV), and modified to permit interactive processing (Table 1). T u m b o w et al. (1984) describes pertinent features of the models and identifies literature dealing with their application.

Data Base.— The data base is comprised of several components. First, it serves as the archive for technical information dealing with I), frontalis. Presently, this information consists of Forest Service SPB Fact Sheets, which are abstracts that have been prepared by various technical experts. Subject matter ranges from utilization of beetle-killed timber to setting control priorities for suppression of beetle populations. This data base can be easily expanded or modified to include new information or delete outdated entries. Second, there is a HELP routine that explains SPBDSS operation and a glossary of terms specific to I), frontalis IPM. Third, many of the models in the model base require complex data input, and the needed data are not always available to the forest manager. Therefore, included in the data base are default values that can be invoked if needed. These default values were obtained by summary of research data collected over a 12 year period. Fourth, there is a user files subsystem. This system, which is private for each user, provides for storage of simulation results from previous operations performed on stands and D. frontalis infestations. In addition to providing a record for the user, data inputs are stored in the system and can be used in subsequent simulations without re-entry.

Data Base Management System (DGMS^ and Model Base Management System (MBMS).— These component programs are nested within the system control program and are the means by which needed elements of the model and data bases are called upon for decision support.

Problem Analysis Program.— This component program, which is also part of the control program, is termed FERRET (Rykiel et al. 1984, Turnbow et al. 1983). We previously discussed FERRET and only emphasize here the importance of this program in directing the user to pertinent elements of the knowledge base on D. frontalis. Since the focus of SPBDSS is on problem solving rather than the"knowledge base, FERRET is an extremely important conceptual as well as operational component. A "stand alone" version of FERRET is available (Turnbow et al. 1983).

Control Program.— The control program directs the operation of SPBDSS. Acting on information received from FERRET, the control program fetches (via the DGMS and MBMS systems) the needed elements of the data and models bases, sequences and links the models when necessary, and generates the reports that will be needed for decision support. This program deals with one of the perplexing issues associated with using models in decision making, namely how to identify and link the available models that are needed for a specific problem. Dialogue Generation and Management System (DGMS). The DGMS is the major interface between the user and SPBDSS. The operations of the program subsys­ tems are, by design, transparent to the user who merely responds to

39 Table 1. Model technology available for use in the southern pine beetle decision support system. Models marked with (*) are interactively implemented within the system.

MODEL MODEL DESCRIPTION SOURCES(S)

TAMBEETLE* southern pine beetle population Feldman et al. (1981); and spot dynamics model Turnbow et al. (1982)

A/E southern pine beetle population Moore (1978) trend model

TFS Spot Growth* east Texas southern pine beetle Hedden and Billings spot growth model (1979); Billings and Hynum (1980)

ARKANSAS (SPB') southern pine beetle populations Stephen and Taha (un­ and spot dynamics model published)3

DAMBUGS* region-wide southern pine beetle Reed (1979) damage projection system

FRONSIM southern pine beetle damage Leuchsner et al. (1977) simulator

SPBEEP* southern pine beetle economic Uhler and Lewis (un­ evaluation procedure published)

TBAP economic analysis procedure Leuchsner et al. (1978) for insect damage

OPTIONS* southern pine forest management Thompson and Vasievich simulator (unpublished)

AHAZARD* southern pine beetle hazard Ku et al. (1980) rating system for Arkansas

PHAZARD* southern pine beetle hazard Belanger et al. (1981) rating system for the Georgia piedmont

THAZARD* southern pine beetle hazard Mason et al. (1981) rating system for east Texas

MS HAZARD B* southern pine beetle hazard Kushmaul et al. (1979) rating system for Mississippi

TRAS timber resource analysis system Larson and Goforth (1970, 1974)

40 Table 1 (continued)

MODEL MODEL DESCRIPTION SOURCES(S)

Brender and growth and yield model for natu­ Brender and Clutter Clutter ral stands of loblolly pine in (1970) Georgia

Burkhart, Parker, growth and yield model for natu­ Burkhart et al. (1972a) and Oderwald ral stands of loblolly pine in the Virginia-North Carolina coastal plain

Burkhart, Parker growth and yield model for old- Burkhart et al. (1972b) Strub, and field loblolly pine plantations Oderwald in the mid-Atlantic coastal plain

Burkhart and Strub growth and yield model for lob­ Burkhart and Strub lolly pine plantations in the (1974) piedmont and coastal plain of Delaware, Maryland, North Caro­ lina, and Virginia

Coile and growth and yield model for lob­ Coile and Schumacher Schumacher* lolly pine plantations (1964)

Goebel and Warner growth and yield model for lob­ Goebel and Warner lolly pine plantations in the (1959) South Carolina piedmont

Lenhart growth and yield model for old- Lenhart (1972) field loblolly pine plantations in the interior west gulf coastal plain

Lenhart and growth and yield model for lob­ Lenhart and Clutter Clutter lolly pine plantations in the (1971) Georgia piedmont

Murphy and Beltz* growth and yield model for even- Murphy and Beltz aged stands of short-leaf pine in (1981) the west gulf region

PTAEDA loblolly pine plantation growth Daniels and Burkhart simulator (1975)

Schumacher and growth and yield model for natu­ Schumacher and Coile Coile* ral stands of loblolly pine (1960)

SeedPTAEDA loblolly pine natural stand Daniels et al. (1979) growth simulator

41 Table 1 (continued)

MODEL MODEL DESCRIPTION SOURCES(S)

Smalley and Bailey Growth and yield model for short- Smalley and Bailey leaf pine plantations in the (1974) Tennessee, Alabama, and Georgia highlands

Sullivan and growth and yield model for natu­ Sullivan and Clutter Clutter ral stands of loblolly pine in (1972) the southeastern coastal plain

USLYCOWG* growth and yield model for lob­ Dell et al. (1979); lolly and slash pine plantations Feduccia et al. (1979) on cutover sites in the west gulf region

YLDTBL growth and yield model for lob­ Myers (1977) lolly pine plantations

SAWMOD sawmill decision model Sinclair (1980)

SPBCOMP* southern pine beetle trend Michaels (unpub­ prediction model lished)

Stephen, F.M., and H.A. Taha, Dept, of Entomology, University of Arkansas, Fayetteville, AR 72701 k Uhler, R.J., and J.W. Lewis, USDA Forest Service, S&PF, 1720 Peachtree Rd., NW, Atlanta, GA 30309 c Thompson, W.A., and J.M. Vasievich, School of Forestry and Environmental Studies, Duke University, Durham, NC 27706

^ Michaels, P.J., Dept, of Environmental Sciences, University of Virginia, Charlottesville, VA 22903

42 systems prompts and then evaluates the reports that are generated. The DGMS is written to be understandable and flexible, allowing the user to "move about" with ease within the system. Keywords such as HELP, BACK, STOP, MODEL, and LIST are some of the simple commands contained in the DGMS. By using these keywords, the SPBDSS user can effectively play the "what if" game that is often necessary in the decision making process.

Implementation of the Southern Pine Beetle

Decision Support System

The accelerated research and development programs on D. frontalis, as well as other important forest insect pests [the gypsy moth, Lymantria dispar (Linnaeus); the Douglas-fir tussock moth Orgyia pseudotsugata (Me Donnough); the eastern spruce budworm, Choristoneura fumiferana (Clements); and the western spruce budworm, £. occidentalis Freeman], resulted in outstanding advancement in our knowledge base on each of these insects. This fact is clear testimony to the value of the approach. However, the proliferation of knowledge created problems for efficient utilization in extension forestry programs. The traditional methods used in forestry extension were not adequate for dealing with a technology that was largely computer-based.

During the last decade computers have become common tools and their use dominates many aspects of extension programs in forestry as well as agricul­ ture. By far the greatest number of applications involve minicomputers and this trend will undoubtedly continue in the future. Distinctions between mini and microcomputers, in terms of speed of operation, storage capacity, and software applications become less with each passing year.

There are several different types of information management systems available for use (e.g., transaction processing systems, management information systems, expert systems, and decision support systems). See Rykiel et al. 1984 for a discussion of the characteristics and uses of these systems. Because of the size of the knowledge base needed for IPM and for most forestry and agricul­ tural production systems, a centralized decision support system, that serves as an archive for models and technical information, is necessary. Such a system can be maintained and updated by a small staff of technically competent indivi­ duals. Access to the system through a terminal or microcomputer is straight­ forward but involves expenses associated with telephone calls and computer time. We contend that these costs are trivial relative to the consequences of uninformed decision making on significant issues dealing with IPM or crop production.

SPBDSS is the first operational decision support system developed and implemented for user testing in forestry or agriculture. The system is main- frame-based because of the size of the knowledge base, the current limitation of microcomputers, and the region-wide nature of the user clientele. The centralized type of system is ca two or three years away from being a common technology used for complicated IPM and agricultural production systems. Systems which deal with the independent component technologies that form the knowledge base of a decision support system must be monitored by highly trained specialists. These individuals problems, selection of pertinent models and technical information relative to the problem, execution of model simulations,

43 preparation of reports, etc. All of these tasks are accomplished automatically by SPBDSS. During the period 1983 to 1985, SPBDSS was demonstrated to forestry extension specialists. The goal of these demonstrations was to obtain criti­ cism of the system, in order to identify needed modification or additions, and to examine the issues associated with implementing the system. In general, modifications and additions to the system can be accomplished without great difficulty or expense. Implementation of the system is also not a serious problem, as most of the users have access to microcomputers or terminals.

In our view the most serious problem, yet to be resolved, centers on how to use the large knowledge base available on D^. frontalis IPM. This statement is not intended as an indictment but rather an observation based on the results of our demonstrations of SPBDSS. The central issue is simply that the exten­ sion specialists have not previously had access to the volumes of technical information and models currently available through SPBDSS. Appropriate uses and applications of this knowledge base have not been identified. We are currently working with the Texas Forest Service and the USDA Forest Service, Forest Pest Management, to resolve this issue.

Future Modifications to the

Southern Pine Beetle Decision Support System

In developing SPBDSS initial emphasis was placed on developing archives for existing models and technical information and providing access to this knowledge base through a problem analysis procedure. That is, the focus was directed to the objective components of the knowledge base. This approach has helped to identify areas of needed new research as well as subjects that are not adequately understood. It is given that our knowledge of D_. frontalis IPM or production systems in forestry and agriculture will always be incomplete and therefore imperfect. Individual judgement and expert opinion will continue to be an important aspect of decision making. Therefore, the most significant modification to SPBDSS at the present time is the inclusion of the wisdom of expert opinion as a component in the system.

Forestry and agriculture have traditionally utilized expert opinion of practititioners as a source of information for decision making. However, the knowledge of experts has never been generally available across the forestry or agricultural communities. Experiences and observations of individuals have usually been confined to local circumstances. Furthermore, the individual experts were rarely interested in documenting their knowledge.

The current structure of the SPBDSS data base is suitable for inclusion of elements of expert opinion. There are certainly areas in our knowledge base where the best information currently available is resident with experts in forest protection and forestry practice. The problem analysis routine, FERRET, would serve to guide the user to the expert opinion as well as the model base and technical information currently in SPBDSS.

In addition to interviews with knowledgeable individuals, the component submodels can be used to develop a base of expert opinion. We believe that one

44 of the important applications of the complex simulation models will be in the development of another class of decision aid known as the "rule based expert system." It may be possible to eliminate the need for simulation models from SPBDSS by summarizing the range of condition predictable by the models. The data from such an exercise could be used to develop the expert system.

Acknowledgements

We acknowledge and thank Drs. R.H. Turnbow and P.J.H. Sharpe for their contributions to the development of SPBDSS. We thank A.M. Bunting, D. Watkins, and L. Gattis for assistance in preparation of the manuscript of this paper. This work was sponsored by Grant No. 6708 of the USDA Forest Service IPM Program and MS 6009 of The Texas Agricultural Experiment Station. The opinions expressed herein are those of the authors.

Literature Cited

Keen, P.G.W. and M.S.S. Morton. 1978. Decision support systems: An organiza­ tion perspective. Addision-Wesley Publ. Co., Reading, Mass. 264 p.

Kulhavy, D.L. and P.C. Johnson. 1983. Southern pine beetle: annotated bibli­ ography, 1868-1982. School of For., Center for Applied Studies, Stephen F. Austin State Univ., Nacogodches, Texas. 95 p.

Loh, K. 1984. Computer-aided problem solving in southern pine beetle manage­ ment. Ph.D. Dissertation (Bioengineering), Texas A&M University. 441 p.

Payne, T.L., R.F. Billings, R.N. Coulson, and D.L. Kulhavy (eds.). 1984. History, Status, and Future Needs for Research in Southern Forest Entomology. Tex. Agric. Exp. Stn. Misc. Publ. 1553. 72 p.

Rykiel, E.J., M.C. Saunders, T.L. Wagner, D.K. Loh, P.E. Pulley, L. Hu, and R.N. Coulson. 1984. Computer-aided decision making and information accessing in integrated pest management, with emphasis on the southern pine beetle. J. Econ. Entomol. 77:1073-1082.

Saunders, M.C., D.K. Loh, R.N. Coulson, E.J. Rykiel, T.L. Payne, P.E. Pulley, and L.C. Hu. 1985a. Development and implementation of the southern pine beetle decision support system. U.S. For. Ser. Symposium Proceedings. Asheville, N.C., Apr. 15-19, 1985. (In Press).

Saunders, M.C., D.K. Loh, T.L. Payne, E.J. Rykiel, P.E. Pulley, R.N. Coulson, P.J.H. Sharpe, and L.C. Hu. 1985b. Procedural guide for SPBDSS, the southern pine beetle decision support system. Tex. Agric. Exp. Stn. Misc. Publ. (In Press).

Sprague, R.H., Jr. 1980. Guest editor's introduction, selected papers on decision support system from the 13th Hawaii International Conference on System Sciences. Data Base 12:2-7.

Thatcher, R.C., J.L. Searchy, J.E. Coster, and G.H. Hertel (eds.). 1980. The southern pine beetle. U.S. Dep. Agric. Tech. Bull. 1613.

45 Turnbow, R.H., L.C. Hu, E.J. Rykiel, R.N. Coulson, and D. Loh. 1983. Proce­ dural guide for FERRET, the question analysis routine of the decision support system for southern pine beetle management. Tex. Agric. Exp. Stn. Misc. Publ. 1533. 21 p.

Turnbow, R.H., D.K. Loh, R.N. Coulson, L.C. Hu, E.J. Rykiel, T.L. Payne and P.E. Pulley. 1984. Component implementation of the decision support system for southern pine beetle management (2nd revision). Tex. Agric. Exp. Stn. - Tex. A&M Univ., Dept, of Entomol. Sci. Rep. Series 84-1. 104 p.

Waters, W.E., R.W. Stark, and D.L. Wood (eds.). 1985. Integrated Pest Manage­ ment in Pine - Bark Beetle Ecosystems. John Wiley & Sons, Inc., N.Y. 256 P-

46 A VIEW OF RESISTANCE TO FUSIFORM RUST IN LOBLOLLY PINE

Glenn A. Snow Principal Plant Pathologist USDA Forest Service Southern Forest Experiment Station Gulfport, Mississippi 39505

The best evidence I have seen for reduction of fusiform rust by the use of resistant pines was presented recently by Schmidt et al. (1985). They examined data from 851 operational pine plantations in Florida and Georgia and found that in high rust hazard areas, rust incidence was significantly less where rust—resistant loblolly pine had been planted. For example, in southwest Georgia, 4116 acres (1666 ha) of susceptible loblolly were planted between 1968 and 1973. At 5 years, rust averaged 44.4 percent and ranged from 0.8 to 82.5 percent among individual plantations. In comparison, 9770 acres (3955 ha) or resistant loblolly were planted in the same area from 1974 to 1979. Fusiform rust in the resistant plantings averaged 12.4 percent and ranged from 0 to 33 percent among planting sites.

I think we can assume that good results are being achieved elsewhere in the southern pine region where fusiform rust is severe and where resistant stock has been planted. The development and use of pine trees with resistance to fusiform rust is therefore a great success story for forestry in the South. Much credit is due to the many people who have been, and still are, involved in these forestry programs.

The status of programs to select and use rust-resistant pines has been addressed in several papers (Powers, et al., 1981; Schmidt, et al., 1981; Wells, et al., 1982; Zobel and Zoerb, 1977). All of these authors indicate that the job is not finished, but should be a continuing process to improve the levels of resistance now in use.

A question that is often asked forest pathologists about fusiform resis­ tance is, "How long can we expect the resistance we are working with to last?" My answer to this question is, "The resistance will hold up indefinitely if it is used properly."

I have given this answer because I believe that the southern pines and Cronartium quercuum (Berk.) Miyabe ex Shirai have evolved together and are approaching a state of balance in which neither the host nor pathogen are threatened. Further, I think the breeding programs involving selection for resistance are strengthening this balance.

The experimental evidence we have for coevolution of these host-pathogen systems is that C. quercuum is specialized to infect different pine species (Kais and Snow, 1972; Powers, 1972), pines of the same species from defined geographic areas (Powers and Matthews, 1980; Powers, et al., 1978), and in­ dividual pine families (Powers, et al., 1978; Snow and Griggs, 1980; Snow, et al., 1976). In addition, considerable levels of resistance occur in all pines that are natural hosts for C quercuum (Grigsby, 1973; Hedgcock and Siggers, 1949; Kais and Snow, 1972; Powers, 1972; Wells and Wakeley, 1966; Wells, et al., 1982). The origin of specialized forms of the pathogen and the resistance

47 in the pine populations can be explained by a process of mutual selection pressure which has occurred during a long association between the hosts and the pathogen (Schmidtling, 1985; Snow, 1985). The special forms appear to be the result of the pathogen adapting to its hosts, while resistance of the pines resulted from natural selection.

The next matter to consider is the evidence that the host-pathogen systems are in balance or equilibrium. £. quercuum commonly occurs on sand, shortleaf, and Virginia pine, yet these species are seldom severely damaged by the patho­ gen. High incidence of the disease is rare on these species and infection results in small round galls which cause little damage to the tree. This situation is exactly what one would expect in a balanced system. The pathogen exists but is relatively innocuous. In contrast, an imbalance in favor of the pathogen exists in loblolly and slash pine stands that are severely damaged by £. quercuum f. sp. fusiforme. Such trees often have long fusoid galls on their stems or galls that extend from the branches into the stem.

We are beginning to recognize a similarity between the host-pathogen systems of shortleaf, sand, and Virginia pine and some resistant populations of loblolly pine. The resistance is manifested by: (1) lack of infection and (2) a tendency towards round gall development when infection occurs.

Geographic sources of resistance are well documented for loblolly pine (Grigsby, 1973; Wells and Wakeley, 1966; Wells, et al. 1982). Trees from the eastern shore of Maryland, western Mississippi, Livingston Parish in Louisiana, and all natural forests west of the Mississippi have moderate to high levels of resistance compared to other sources of loblolly pine. Select trees from these areas provide excellent sources of resistance for seed orchards. Also, stock from bulk seed lots of Livingston Parish seed have been planted extensively in much of the southern pine region (Wells, in press).

The tendency of some loblolly pines to form round galls has been observed in inoculation experiments with seedlings grown from trees in Livingston Parish, Louisiana (Snow, et al. 1982). Seedlings from 10 parent trees were inoculated with five sources of rust inocula. The galls that formed on seed­ lings from three of the trees were rounder than those on the other trees. In addition, two inocula caused rounder galls on all trees than did the other three inocula. Gall shape, therefore, appears to be controlled by the genetics of both the host and the pathogen.

If the trait for round gall development has an advantage for fitness over long galls, one would expect a tendency for galls to be round in resistant populations of loblolly pine. We recently examined fusiform rust galls in nine pine plantations to determine if the gall shape differed by seed source and planting location. Gall length and width were measured and a gall form value (gall length/gall width) was derived from each gall (Table 1). The largest values were from galls on slash pines grown from a seed source known to be susceptible to fusiform rust. A susceptible source of loblolly pine from Mississippi also had higher gall form values than all but one of the other loblolly seed sources. Trees grown from the Livingston Parish seed sources tended to have low gall form values wherever they were planted. The trees with the lowest values (X = 2.43), and roundest galls, were in a loblolly planting near Apple Springs, Texas. These observations support the hypothesis that there is a tendency for round gall development on resistant loblolly pine

48 Table 1. Average gall form values for fusiform rust galls in nine pine plant­ ings.

Number Mean Planting location Species Seed source of galls gall form

Harrison Co., Miss. Slash South Miss. 50 4.57

Harrison Co., Miss. Loblolly South Miss. 50 3.78

Harrison Co., Miss. Loblolly Livingston Parish, La. 50 3.50

Pearl River Co., Miss. Loblolly Livingston Parish, La. 100 3.20

Livingston Parish, La. Loblolly Livingston Parish, La. 35 3.29

Walker Co., Tex. #! Loblolly Texas 30 3.38

Walker, Co., Tex. #2 Loblolly Texas 37 3.89

Trinity Co., Tex. #1 Loblolly Texas 28 3.42

Trinity Co., Tex. #2 Loblolly Texas 51 2.43

Gall form is derived by dividing gall length by gall diameter. Round galls have low values; long galls have higher values.

49 because both Livingston Parish and Texas seed sources have moderate to high levels of resistance to fusiform rust.

The similarity of the host-pathogen system on loblolly pine with that of shortleaf pine seems important. I think that foresters are proceeding in the direction of a balanced system when they select and use resistant loblolly stock by whatever means— geographic seed sources, seedling seed orchards, selection and breeding, or simply natural regeneration. These efforts certain­ ly should be continued. In addition, we need to learn more about how to achieve and maintain balanced systems for the southern pine and (]. quercuum f. sp. fusiforme.

Summary

Specialization of Cronartium quercuum (Berk.) Miyabe ex Shirai on southern pines, coupled with the levels of resistance that exist in the pine popula­ tions, indicates that the pines and the pathogen have coevolved in response to mutual selection pressure. This process appears to have resulted in balanced systems for sand, shortleaf, and Virginia pine, in which survival of the hosts or pathogen is not threatened. A similar balance is apparently being ap­ proached in certain loblolly pine populations where the frequency of resistant individuals is high to C_. quercuum f. sp. fusiforme and a tendency for round gall formation, a relatively innocuous infection, has been observed. Selection and use of resistant trees are efforts that must be sustained to strengthen and maintain this balance.

Literature Cited

Grigsby, H.C. 1973. South Carolina best of 36 loblolly pine seed sources for southern Arkansas. South. For. Exp. Stn., USDA For. Serv. Res. Pap. SO-89, 10 p.

Hedgcock, G.G., and P.V. Siggers. 1949. A comparison of pine—oak rusts. USDA Tech. Bull. 978, 30 p.

Kais, A.G., and G.A. Snow. 1972. Host response of pines to various isolates of Cronartium quercuum and Cronartium fusiforme. In: Biology of rust resistance in forest trees: Proceedings of a NATO-IUFRO Advanced Study Institute, USDA Misc. Pub. No. 1221, p. 495-503.

Powers, H.R., Jr. 1972. Testing for pathogenic variability within Cronartium fusiforme and C_. quercuum. In: Biology of rust resistance in forest trees: Proceedings of a NATO-IUFRO Advanced Study Institute, USDA Misc. Pub. No. 1221, p. 505-509.

Powers, H.R., Jr., and F.R. Matthews. 1980. Comparison of six geographic 7°ll41Sll°4f3 lobl°lly pine for fusiform rust resistance. Phytopathology

Powers, H.R., Jr., F.R. Matthews, and L.D. Dwinell. 1978. The potential for increased virulence of Cronartium fusiforme on resistant loblolly Dine Phytopathology 68:808-810.

50 Powers, H.R., Jr., R.A. Schmidt, and G.A. Snow. 1981. Application of genetic disease resistance for the control of fusiform rust in intensively managed southern pine. Phytopathology 71(9):993-997.

Schmidt, R.A., H.R. Pwers, Jr., and G.A. Snow. 1981. Application of genetic disease resistance for the control of fusiform rust in intensively managed southern pine. Phytopathology 71(9):993—997.

Schmidt, R.A., R.C. Holley, and M.C. Klapproth. 1985. Results from operations plantings of fusiform-rust-resistant slash and loblolly pines in high- rust-incidence areas in Florida and Georgia. In: Proc. IUFRO Rusts of Hard Pines Working Party Conf. S2.06-10, Athens, GA, Oct. 1984, p. 33-41.

Schmidtling, R.C. 1985. Co-evolution of host/pathogen/alternate host systems in fusiform rust of loblolly and slash pines. In: Proc. IUFRO Rusts of Hard Pines Working Party Conf. S2.06-10, Athens, GA, Oct. 1984, p. 13-19.

Snow, G.A. 1985. Coevolution of Cronartium quercuum with hard pines in eastern North America. In: Proc. IUFRO Rusts of Hard Pines Working Party Conf. S2.06-10, Athens, GA, Oct. 1984, p. 1-12.

Snow, G.A., and M.M. Griggs. 1980. Relative virulence of Cronartium quercuum f. sp. fusiforme from seven resistant families of slash pine. Phytopathologia Mediterranea 19:13-15.

Snow, G.A., R.J. Dinus, and C.H. Walkinshaw. 1976. Increase in virulence of Cronartium fusiforme on resistant slash pine. Phytopathology 66:511-513.

Snow, G.A., W.L. Nance, and E.B. Snyder. 1982. Relative virulence of Cronartium quercuum f. sp. fusiforme on loblolly pine from Livingston parish. In: Proc. of the Third International Workshop on the Genetics of Host-Parasite Interactions in Forestry, Wageningen, the Netherlands, Sept. 1980, p. 243-250.

Wells, 0.0. [In press] Use of Livingston Parish, Louisiana, loblolly pine by forest products industries in the Southeastern United States. South. J. Appl. For.

Wells, 0.0., and P.C. Wakeley. 1966. Geographic variation in survival, growth, and fusiform rust infection of planted loblolly pine. For. Sci. Monogram 11, 40 p.

Wells, 0.0., G.L. Switzer, and W.L. Nance. 1982. Genotype-environment inter­ action in rust resistance in Mississippi loblolly pine. For. Sci. 18(4):797-809.

Zobel, B., and M. Zoerb. 1977. Fusiform rust management strategies in concept: Reducing fusiform rust in plantations through control of the seed source. In: Management of fusiform rust in southern pines, Proc. of sym. sponsored by South. For. Dis. and Insect Res. Counc., Gainesville, FL, Dec. 1976, p. 98-109.

51 INFLUENCE OF FORESTRY PRACTICES ON BARK BEETLE POPULATIONS: A PERSPECTIVE

T. Evan Nebeker Mississippi State University

Bark beetles have been a part of the southern forest ecosystem for hun­ dreds of years, having co-evolved with their hosts without either becoming extinct. Because we have elected to maintain a portion of our forests in a subclimax state, i.e. pine, we have also passively elected to support bark beetle populations by providing them with suitable food resources and habitats within which to reproduce. That is to say, from our current understanding of the resource preferences of bark beetles, we are perpetuating the preferred host species of the bark beetles throughout their range. One might also speculate that the bark beetles maintain forest in their subclimax state by going through major population fluctuations that insure that resources will be available for future generations through successional changes and without man co-existence would be observed. On the other hand bark beetles tend to move a forest towards the climax state by removing the subclimax species, if hardwood exists in the stand.

As we look back at the history of forest stand development, we see that during the 1800's much of the land was cleared for cultivation which severely reduced the available resources for bark beetle populations. Periodic out­ breaks have been noted since the late 1700's and early 1800's (Price and Doggett 1978). Both the frequency and severity of outbreaks have increased during the last 20 years. Within the past decade and a half, bark beetles have caused a great deal of damage to our forests. The underlying cause of these outbreaks may be changing stand conditions (Hedden 1978) and increased acreage of suitable host type. Almost all areas of the south are experiencing in­ creases in both pine growing stock and sawtimber volume (Earles 1976; Knight and McClure 1979; Renewable Resources Evaluation Research Work Unit 1978). These increases are primarily due to the development of young pine stands established on retired croplands between 1940 and the early I960's. This trend will insure that during the next 20 to 30 years increasing numbers of pine stands will become available for bark beetle attack.

The intent of this paper is to: 1) describe the types of commercial forest settings where bark beetles are most likely to cause problems; 2) explore the possible outcomes of particular forestry practices if implemented or followed, i.e. hazard rating, clear cut and/or subsequent types of thinnings; and 3) describe what the future might hold for bark beetle related problems in light of contemporary and projected forestry practices.

Stand Conditions

In the case of the southern pine beetle, Dendroctonus frontalis Zimmermann, infestations occur more often in slow growing, overstocked pine stands where individual tree vigor and resistance to attack are low. Hicks (1980), Belanger and Malac (1980) and Kulhavy (1984) have provided summaries that relate site and stand information associated with bark beetle attack. Factors such as landform, water regime, soil texture, soil chemical properties site index, soil depth, pH, stand density, radial growth, species composition, average stand age, height, diameter, live crown ratio, etc. have been utilized

52 in describing the conditions associated with bark beetle infestations. Suscep­ tible stands in the three major geographic regions (Southern Coastal Plain, Piedmont and Southern Appalachians) show basically the same characteristics; 1) dense stocking, 2) sawtimber size, 3) declining radial growth, 4) poorly drained soil locations, and 5) high percentage composition of shortleaf and/or loblolly pine. It is also important to note that bark beetle infestations are also associated with various types of disturbances. One of the major distur­ bances that the southern pine beetle is found in association with is lightning struck trees. In some cases as high as 80% of the infestations initiated during a given time period were associated with a lightning struck trees.

Forestry Practice Implementation

Numerous hazard rating systems, which relate site and stand conditions associated with bark beetle infestations, have evolved as a result of the mass of data that had been collected over the past decade and the variation in conditions observed throughout the range of the southern pine beetle. However, many of the systems that are currently being utilized and recommended for implementation, do not include information concerning the current status of the beetle population nor the physiological conditions (characteristics) of the trees in the stand. Conceptually, difficulties can arise in rating stands from year to year when the beetle population is disregarded. This idea is presented in Fig. 1 from Nebeker and Hodges (1983). If the population is low (endemic), attacked trees should be in stands that have received a high hazard rating. However, due to the approach (generally discriminant analysis) taken in the development of these rating systems this may not be true. That is to say, a stand classified as high hazard by a system developed during an epidemic period may actually have a low hazard during an endemic period.

In addition, the rating systems give no consideration to the possibility of differences between individual trees physiologically (genetically) which may result in differences in susceptibility to beetle attack. It is therefore possible that current systems for rating stands could rate a stand as high hazard even though it is composed of resistant trees. Paine et al. (1984) having expanded this general idea, point out that the risk (a probability statement) of a bark beetle infestation starting and growing, result from the interaction of stand hazard (a function of host tree, site, and stand condi­ tions) and beetle population (a function of population abundance and physio­ logical condition). Problems associated with the validation of hazard rating schemes may be directly related to the lack of consideration of population levels at the time the systems were developed.

Another major concern related to the utilization of hazard rating systems is the lack of benefit/cost analysis. The primary goal of hazard rating system developers has been to provide information for the land manager that will assist in the decision making process. Given a series of stands with different hazard ratings, it would seem wise to first schedule cultural practices in those stands which have been classified as very high hazard and assign lower priorities to very low or low hazard stands.

Information regarding the economic analysis of these rating systems and subsequent cultural practices that might be applied as a result of the incor­ poration of the hazard rating information into a comprehensive plan is lacking. Further, the process of selecting a system to utilize, from an economics point

53 of view, has not been taken into consideration. Two questions that need to be addressed are: Which hazard rating system to select and how frequently should the hazard ratings be updated to be in step with current and changing stand conditions?

Forestry Practices and their Consequences

Do Nothing.— In the pest management decision-making process, one tactic that is always considered as an option in a benefit/cost analysis is that of Doing Nothing (Nebeker et al. 1984). The same is true with forestry practices. Within the forest management realm, the decision to do nothing is also a viable option. What are the implications of doing nothing in relation to bark beetle populations? From an historical perspective on can expect periodic outbreaks to occur. As the host acreage increases, and directly related to the overall beetle population at a particular point in time, one would expect a propor­ tional increase in tree mortality. That is to say, if the population is in an epidemic state vs. an endemic state, considerably more trees will be lost and acreage infested. Two recent examples of this is in the case of The Big Thickett and Four-Notch areas in Texas. Similar experiences have been observed thrdughout the south.

Clear cut.— With respect to geographic areas that have had a long history of repeated infestations, a forestry practice that one might consider is clear cutting the high hazard stands. This reduces the available resource material for the southern pine beetle. However, if care is not taken in the harvesting operation and the remaining slash is left in piles, then the resources which the engravers (Ips spp.) prefer is increased and potential mortality to surrounding stands may occur. This has not been observed to create any major problems in the southeastern region (Nebeker et al. 1985). However, with respect to some of the western species such as the Douglas-fir beetle, D. pseudotsugae Hopkins, this may not be necessarily true since large populations have been observed building up in large blow-down areas.

Thin.— The forestry practice most frequently recommended to reduce stand hazard is thinning. The influence of thinning on host-susceptibility to bark beetles and associated pest problems has been investigated in a preliminary manner in the southern region-Gulf Coastal Plain (Nebeker and Hodges 1983; Nebeker et al. 1983; Nebeker et al. 1985). The primary objectives of these studies have been aimed at determining the effect of thinning intensity on the establishment and potential spot growth of southern pine beetle infestations. Secondary objectives have been directed at investigating changes in host condition as a result of thinning to hopefully explain changes in vigor and/or susceptibility to bark beetle attack following thinning operations.

The literature on thinning is extensive for the major southern pine species. Published information on its relationship to pest problems however is limited. We (Nebeker et al. 1985) have provided a treatise on the concept of thinning, reviewed and summarized thinning research, surveyed current field practices, and related the positive and negative aspects of these practices to current or potential destructive agent problems. Further, we included sugges­ tions concerning management approaches that can help to minimize losses.

Any thinning strategy must consider the potential hazards associated with such intensive silvicultural practices. Bark beetle infestations are often

54 associated with poor tree vigor which may be altered in response to the thin­ ning. Tree vigor being basically related to site, tree, stand, and environ­ mental conditions, the development of bark beetle outbreaks is therefore strongly influenced by these conditions. Though vigor is difficult to quantify, radial growth rate can serve as a strong indicator of tree condition or vigor. Other factors that affect vigor include: age, stand density, soil texture and type, drainage patterns, and stand disturbances associated with cultural practices. Poor tree vigor is usually associated with densely stocked stands and indicated by declining or slow radial growth. These conditions can be readily alleviated by thinnings, especially those that remove the lower crown classes. These types of thinnings eliminate the less vigorous or weakened individuals which are the prime targets for bark beetle attack.

Reduced competition pressure enhances the vigor of residual trees. Thinning stands back to 70-100 ft2/acre basal area reduces the hazard to bark beetle attack and may also help to slow spot growth (Fig. 2) if an attack does occur (Nebeker and Hodges 1983). Timing of the thinning operations is also critical. Thinning during periods of reduced beetle activity, i.e. winter, is recommended. However, one must consider the impact on the site from rutting and damage to the residual stems. Thinnings during periods of beetle activity (May-October) can be done if care is taken in the distribution of the slash material. Slash distribution patterns are associated with the type of thinning system utilized. If tops remain piled around the base of the residual stems this increases the probability that residual stems will be attacked by bark beetles, particularly Ips spp. These beetles are attracted to the slash material where they reproduce and upon emergence attack the nearest standing tree or are reabsorbed into the slash. Hence, it is critical that considera­ tions be given to the slash distribution pattern in the thinning operation. Distributing the slash throughout the site also increases the bearing strength of the soil. In addition, logging traffic over the slash and subsequent bark removal reduces the resources available for bark beetle reproduction.

In general, thinning to reduce bark beetle hazard is recommended when basal area approaches 120 ft2/acre, or when live crown ratios drop to about 40% provided the preventive approach to pest management is being taken. If the reactive approach, do nothing—except when an infestation is observed, is chosen then higher basal areas may be reached before scheduling a thinning. However, the probability of attack will increase as the resident beetle population increases. Disturbances in the unthinned settings, i.e. lightning, increase the probability of successful beetle attack and spot spread. In contrast, a disturbance such as lightning in a thinned stand may result in the death of that tree and bark beetle may colonize the struck tree, but the subsequent probability of spot growth is lower.

Carefully executed thinning will stimulate radial growth, reduce evapo- transpiration, and increase rain throughfall. The reduction in evapotranspira- tion slows down the exhaustion of groundwater supply and favors continued diameter growth. The prevention of severe water stress results in lower monoterpene concentration and higher levels of resin acids which could be involved in making the stand less attractive to beetles (Hodges and Lorio 1975). Pine stands in low-lying areas are frequently subjected to flooding and become attractive to bark beetle attack. In these areas, thinning alone will not correct the problem. Additional forestry practices such as drainage to divert excess water may be needed.

55 Fig. 1. Conceptual relationship of hazard class determination In relation to population level (after Nebeker and Hodges 1983).

5 6 BA (m*2/ha)

Fig. 2. Expected number of trees, after spot growth, to be killed during a subsequent U month period following an Initial single tree Infestation such as a lightning strike (after Nebeker and Hodges 1983 and Nebeker et al. 1983).

57 Any thinning strategy, in the future, to reduce the bark beetle hazard should be compatible with management goals and consider such things as site and stand factors, equipment, seasonality, and product objective. Consideration of other potential hazards, i.e. diseases, that might conflict with bark beetle recommendations must also enter into the decision making process.

Acknowledgements

I wish to express my sincere thanks to my colleagues Jeff Schmitt, Ron Honea, Jack DeAngelis, Catalino Blanche and John Hodges for the hours of stimulating discussion and sharing of ideas openly and freely. I'm grateful for their review and suggestions concerning this manuscript. With their assistance, a great deal of new information concerning the general subject area of host/insect/microorganism interactions as influenced by forestry practices will becoming out in the near future.

References

Belanger, R.P. and B.F. Male. 1980. Silviculture can reduce losses from the southern pine beetle. USDA Agr. Handbook No. 576.

Earles, J.M. 1976. Forest statistics for southeast Texas counties. USDA For. Serv. Resour. Bull. SO-58. 21 p.

Hedden, R.L. 1978. The need for intensive forest management to reduce south­ ern pine beetle activity in east Texas. So. J. Applied for. 1:19-22.

Hicks, R.R., Jr. 1980. Climatic, site, and stand factors. _In_ Thatcher, R.C. et al. (eds). The Southern Pine Beetle. USDA Tech. Bull“ l631. 55-68.

Hodges, J.D. and P.L. Lorio, Jr. 1975. Moisture stress and composition of xylem oleoresin in loblolly pine. For. Sci. 21:283-290.

Knight, H.A. and J.P. McClure. 1979. Southern Carolina's forests. USDA For. Serv. Resour. Bull. SE-51. 66 p.

Kulhavy, D.L. 1984. Hazard rating and site/stand factors. In Payne, T.L. et al. (eds). History, status, and future needs for entomology research in southern forests. Tx. Agr. Exp. Stat. MP-1553. 24-29.

Nebeker, T.E. and J.D. Hodges. 1983. Influence of forestry practices on host-susceptibility to bark beetles. Z. ang. Ent. 96:194-208.

Nebeker, T.E., D.M. Moehring, J.D. Hodges, M.W. Brown, and C.A. Blanche. 1983. Impact of thinning on host susceptiblity. In Jones, E.P., Jr. (ed). Proceedings Second Biennial Southern Silvicultural Research Conference. USDA Gen. Tech. Rept. SE-24. 376-381.

Nebeker, T.E., R.F. Mizell III, and N.J. Bedwell. 1984. Management of bark beetle populations: Impact of manipulating predator cues and other control tactics. In Gamer, W.Y. and J. Harvey, Jr. (eds). Chemical and Biologi— cal Controls in Forestry. ACS Symposium Ser. 238. 25-33.

58 Nebeker T.E., J.D. Hodges, B.K. Karr, and D.M. Moehring. 1985. Thinning practices and associated pest problems in southern pines. USDA Gen. Tech. Retp. (In Press).

Paine, T.D., F.M. Stephen, and H.A. Taha. 1984. Conceptual model of infesta­ tion probability based on bark beetle abundance and host tree suscepti­ bility. Envir. Entomol. 13:619-624.

Price, T.S. and C. Doggett. 1978. A history of southern pine beetle outbreaks in the southeastern United States. Ga. For. Comm. Rep. 31 p.

Renewable Resources Evaluation Research Work Unit. 1978. Forest statistics for Mississippi counties. USDA For. Serv. Resour. Bull. SO-69. 86 p.

59 PROSPECTS FOR OAK WILT CONTROL IN TEXAS

D.N. Appel Texas Agricultural Experiment Station Texas A&M University College Station, TX

R.L. Lewis, Jr. USDA Forest Service Southern Hardwood Research Laboratory Stoneville, MS

Following the discovery of oak wilt in 1942 in Wisconsin, many north­ eastern and midwestem states reported the disease and developed a variety of management techniques. Few of these programs are still active. In some cases, the control efforts were discontinued due to lack of any substantial success in reducing losses. Also, catastrophic losses never materialized and efforts to control the disease were eventually considered unnecessary (MacDonald and Hindal, 1981).

Discovery of the widespread distribution of Ceratocystis fagacearum (Bretz) Hunt, the oak wilt pathogen, in Texas has revived interest in develop­ ing a satisfactory control program (Appel and Maggio, 1984; Lewis, 1977; Lewis and Oliveria, 1979). Oak wilt is responsible for enormous losses of live oaks (Quercus Virginia Mill, and £. fusiformis Small) in the central portion of the state (Appel and Maggio, 1984). These losses are particularly unusual because the disease was not considered a threat to southern oaks (Tainter and Gubler, 1973>. In addition to survey activities, recent studies have dealt with comparing the behavior of fagacearum in Texas to characteristics of the pathogen and oak wilt elsewhere. Oak wilt is found throughout 22 states in the U.S. and there are diverse regional differences that may influence the inci­ dence and severity of the disease.

Initial efforts to manage oak wilt in Texas derive from control techniques developed in other states. Although it is premature to determine the efficacy of these treatments, our observations on the occurrence of oak wilt in Texas could be valuable in avoiding mistakes and formulating future control programs for ranchlands and urban forests. In this presentation we will first address the wide array of oak wilt control techniques that have been proposed and implemented during the 43 years of research in the U.S. Several excellent reviews on oak wilt (Gibbs and French, 1980; MacDonald and Hindal, 1981; True, et al., 1961), are available so we will highlight only those factors relevant to current observations in Texas. The Texas oak wilt epidemic will then be contrasted to the occurrence of oak wilt in those areas where the traditional control methods were deployed. Finally, we will discuss results from the limited testing for oak wilt control in Texas.

Transmission of Ceratocystis fagacearum.—— Most oak wilt control measures were based on the evidence that £. fagacearum spreads in two ways. The first, termed local spread, is between adjacent trees through root grafts and is generally limited to 50 ft. or less per year. Long distance transmission, the second form of spread, results from the activities of insect vectors. In most areas where oak wilt occurs, nitidulid beetles are considered the most

60 important vectors. These beetles acquire inoculum from fungal mats formed under the bark of diseased red oaks (Erythrobalanus). The beetles then transmit conidia and ascospores from the surface of the mats to wounds on healthy trees.

The limitations of each of these methods of transmission may result in the failure of £. fagacearum to cause catastrophic losses (Gibbs and French, 1980; MacDonald and Hindal, 1981). Stand density and soil depth have been shown to influence tree-to-tree spread of the pathogen through root grafts (Gillespie and True, 1959; MacDonald and Hindal, 1981). The importance of root grafting therefore varies with location and is considered most important in midwestern states, where dense stands of northern pin oak ((£. ellipsoidalis E. J. Hill) are extensively root-grafted (Gibbs and French, 1980). Transmission through root grafts is less important in the eastern and southern range of oak wilt.

Mat formation occurs only on infected red oaks, and is influenced by season of infection, tree condition, temperature, and rainfall (Gibbs and French, 1980, MacDonald and Hindal, 1981). The percentage of wilted red oaks producing mats varies throughout the range of fagacearum. In West Virginia, mats may form on 80% of diseased trees (True, et al., 1961), whereas mats rarely form on infected red oaks in Missouri (Jones and Bretz, 1958). Mat production is usually greatest during the spring, when trees are most suscepti­ ble and nitidulids are most active, but they are also formed in October and November. White oaks (Leucobalanus) have consistently demonstrated resistance to C. fagacearum. Intraspecific root grafting between susceptible red oaks and whiTe oaks is not sufficiently common to be considered important (Epstein, 1978).

Control measures.— Control measures were tested and implemented by states according to resources and characteristics of the disease within a given region. Most of these measures had two common objectives: i) preventing mat formation, and, ii) stopping local spread through root grafts. States tested and developed program that incorporated both of these objectives (French and Stienstra, 1980; Himelick and Fox, 1961; Jones and Bretz, 1958; True, et al., 1961).

A disease survey was usually considered an essential part of any compre­ hensive oak wilt control program. Most surveys utilized low-speed, high—winged aircraft flying at relatively low altitudes in a systematic pattern (True, et al. 1961). Symptomatic trees were distinguished from surrounding vegetation with little difficulty and could even be separated from trees debilitated by other causes. The locations of diseased trees were noted and any follow-up experimental or control measures could be conducted by ground crews.

Two states that established large scale, intensive control programs were Pennsylvania and West Virginia (Jones, 1971). In Pennsylvania, when infection centers located with aerial surveys, were controled by cutting all trees within 50 ft of a diseased tree of the same speciesas the diseased tree. The remaining stumps were treated with the herbicide Ammate to hasten root kill and prevent spread through root grafts. Infested portions of West Virginia also were surveyed with low flying aircraft (True, et al. 1961). All diseased trees found in West Virginia were completely girdled to the heartwood at a convenient height and bark was removed from the trunk and buttress roots below the girdle. These measures were intended to promote drying and reduce the numbers of fungal

61 mats on red oaks. Root graft spread was considered inconsequential in West Virginia, so no measures were taken to prevent this means of transmission.

The Pennsylvania and West Virginia methods of control were not consistent­ ly successful. When evaluated under experimental conditions at a wide range of sites, the former method proved to be most successful in reducing infections in immediate vicinities of active, treated infection centers (Jones, 1971). Although the West Virginia program did not reduce losses as well as the Pennsylvania method, it was less expensive and large numbers of healthy trees were not destroyed.

Variations on these two control methods have been tested and implemented by a number of states. In Missouri, an isolation method was tested by poison­ ing all oaks within 50 ft. of diseased trees and allowing them to stand (Jones and Bretz, 1958). Sanitation also was practiced by cutting and burning diseased trees and healthy adjacent trees. None of these methods were successful under Missouri conditions. The failure to control the disease was attributed to difficulties in detection of diseased trees, particularily white oaks, at the time of survey.

Disease survey and early detection were emphasized for oak wilt control in Illinois (Himelick and Fix, 1961). Poison "barriers" were established around diseased trees by applying various herbicides in ax frills made on diseased and adjacent, healthy trees. To reduce the number of healthy trees sacrificed, and reduce the cost of the operation, the diameters of diseased and healthy trees were related to likely grafting distances. Substantial reductions in local spread were achieved when poison barriers were established around currently infected trees, and infected trees killed in the three years prior to treat­ ment. Prediction equations were recently formulated in Wisconsin (Menges and Loucks, 1984) that utilize inter-tree distances and tree diameters as criteria for assessing disease hazards and barrier placement.

Current recommendation for oak wilt control in Minnesota emphasize mechanical and chemical root pruning (French and Stienstra, 1980) deep girdling of diseased red oaks is recommended to prevent mat formation, and avoidance of pruning wounds in the spring.

Although disease development and control methods vary regionally, certain problems are consistently encountered when disease management is attempted. Local spread of the pathogen is very erratic, and difficulties are encountered in measuring the efficacy of any treatments. Latent infections in resistant oaks are difficult to defeat and often are suspected to contribute to spread. Disease patterns implicate vectors other than nitidulids in overland spread (Bowen and Merrill, 1982). Presumably these alternate vectors require mat formation for inoculum acquisition and are usually not targeted in traditional methods of control. As with any forest tree disease, the survey and treatment of large numbers of trees over wide geographic areas has proven expensive and difficult to implement.

The Texas oak wilt epidemic compared to other regions.— Ceratocystis fagacearum has now been found in 32 Texas counties, largely within the central portion of the state. Most of these counties are on the Edward's Plateau, described as a hilly outcrop consisting of oak-juniper-mesquite savanna. The area is fairly arid (24-32 in. precipitation/year), has very thin soils, and

62 has been used primarily for grazing and rangelands in the past. The major oak in this area is Q. fusiformis, or west Texas live oak. This species is be­ lieved to hybridize with southern live oak (Q. Virginia) beyond the south­ eastern edge of the plateau where several counties also contain oak wilt. Spanish oak (Q. texana Buckl.) and blackjack oak (Q. marilandica Muenchh.) are the major red oaks in this area, and they respond to infection in a manner similar to diseased red oaks found in other states (Appel and Maggio, 1984: Appel, et al., 1983).

The responses of live oaks to natural infection by C. fagacearum are unique to those described for other oaks. Most live oaks are extremely susceptible to the pathogen, and die within 6 months to a year after initial symptom appearance. However, a noticeable proportion of trees survive the disease and lose varying amounts of crown. The foliage on diseased live oaks exhibit distinct symptoms of veinal necrosis and tipburn. Post oaks ((J. stellata) are also prominent on the Edward's Plateau and react to infection as other white oaks do. Other minor Quercus spp. on the Edward's Plateau also have exhibited susceptibility to natural infection by £. fagacearum.

Another characteristics influencing and oak wilt in Texas is the rhizomaceous habit unique to live oaks. This propensity to form root sprouts appears to local spread of C_. fagacearum. Common root systems are assumed to be pervasive, especially in the large, homogenous stands of live oaks that have developed with the assistance of fire control, ranching and selective removal of other trees by man (Appel and Maggio, 1984). The maintenance of common root systems in addition to root grafting, may account for the extremely large and rapidly expanding oak wilt centers observed in central Texas. A random selection of 38 oak wilt centers located in the Kerrville-Bandera survey area of Texas ranged 1 to 57 acres in size. Hundreds of trees are commonly found in the larger oak wilt centers (Fig. 2). In contrast, during a five-year study to control oak wilt in Missouri, 784 oak wilt centers were located averaging 2.3 diseased trees per center (Jones and Bretz, 1958). In West Virginia, infection centers commonly contain two to five dead trees, although they may include as many as 30 to 50 diseased trees on an acre of land (Gillespie and True, 1959).

The opportunity for long distance spread of £. fagacearum in Texas is greater than originally expected. Fungal mats have been found on Spanish oaks and blackjack oaks when trees are in the proper stage of colonization and environmental conditions are favorable (Appel, et al., 1985). During the 1983-1984 season, peak mat formation on 11 diseased Spanish oaks near Burnet, TX, occurred during March-May, 1984. However, mats began forming on trees in November and continued to form throughout the winter. The seasonal progression of mat formation on the trees is shown in Table 1. In Figure 1, the weekly number of free flying nitidulids at the same location, trapped in 52 baited jars, is depicted. Nitidulid populations reached peaks during the period of maximum mat formation, and thus have ample opportunity to acquire inoculum and transmit the fungus to healthy trees. Of 863 free-flying beetles captured during March-June, 18 (.02%) were found to be contaminated with £. fagacearum. Although these are preliminary results, nitidulid beetles are probably impor­ tant oak wilt vectors in Texas, and behave in a similar manner to nitidulids found in the midwestern and eastern U.S.

Attempting to Control Oak Wilt in Texas.— Extensive surveys for oak wilt were initiated in Texas in 1982. Infrared, aerial photography was chosen as

63 Table 1. Occurrence of fungal mats on Spanish Oaks (Quercus texana) infected with Ceratocystis fagacearum.

Month of Inspection (1983-■1984)a

Tree No. Oct. Nov. Dec. Jan. March April

1 + + +

2 - + + + + —

3 - - - + - 4 - - - + + 5 - - + - + — 6 - - + - + + 7 — + + + - - 8 9 — ___ —m 10 - --- + — ii +

A + means fresh, fungal mats were found at the time of inspection, wherease a - means fresh mats were found. the best method to detect oak mortality scattered over wide areas and with relatively low numbers of personnel. As a result of these surveys, oak wilt was established as the most serious disease of live oaks in central Texas (Appel and Maggio, 1984). Several extremely intense, localized epidemics were found and measured. For example, in the Kerrville—Bandera survey area of 96,000 acres, oak wilt was estimated to be responsible for 866 infection centers (Appel and Maggio, 1984). Centers were found that ranged from a few trees up to 200 acres in size. In contrast, in a similar survey area just 16 mi north of Kerrville, no active oak wilt centers were located with aerial photography. There were no obvious differences in geography, host density, or climate that might account for this disease distribution. Further survey will be necessary to determine whether the disease is intensifying at new locations or the range is expanding within the state.

The disruption of common root systems is the most direct way to control root-to-root spread of £. fagacearum in Texas. Over the past five years, pilot projects utilizing trenching and tree removal have been established and moni­ tored at nine oak wilt centers of varying sizes and host densities. Because of differences among sites such as host composition, soil depth, and machinery used to mechanically disrupt roots, the efficacy of trenching has been difficult to evaluate. In most cases, the trenches are only partially successful in inhibiting spread of the pathogen.

Figure 2a depicts a typical oak wilt center comprised of 11.3 acres of diseased trees surrounded by a large homogenous stand of healthy live oaks. A trench 3,000 ft. long was dug around this center with a bulldozer and ripper, and all diseased or suspect trees were rogued and burned (Figure 2b). The

64 NO. OF B EETLES Figure 1. Weekly numbers of nitidulid beetles trapped in 52 baited jars baited 52 in trapped beetles nitidulid of numbers Weekly 1. Figure ac Arl a Jn Jl Ags Sept August July June May April March oae truhu a cieokwl cne t unt TX. Burnet, at center wilt oak active an throughout located DATE

Figure 2. Drawing made from an aerial photograph of an oak wilt center depict­ ing vegetation crown cover comprised of live oaks: A. The 11.3 acre oak wilt center in 1983 with diseased and dead trees still standing. B. The same aread in 1984 following removal of diseased trees and adjacent healthy trees, and, digging a 3000 ft. trench to stop local spread of Ceratocystis fagacearum through root grafts.

66 trench subsequently failed to stop C_. fagacearum at two locations, and further tree removal and trenching were carried out. The failure of mechanical trench­ ing at this and other locations is attributed to improper placement of the trench. As a result, removing several symptomless "buffer" trees is now recommended in between the diseased trees and trench. Many apparently healthy trees are destroyed in the process, but there is insufficient knowledge concerning root colonization, symptom development, and rate of fungal spread to improve the recommendation.

Trenching is believed to be a viable control measure in ranchlands where there is a low incidence of oak wilt and a low population of Spanish oaks. In contrast, the extremely high incidence of oak wilt in the Kerrville-Bandera area and potential for long distance spread due to mat formation on Spanish oaks makes trenching of questionable value. In these areas, measures must be taken to stop long distance spread. One way to accomplish this is to destroy infected Spanish oaks, but these often occur in high numbers in inaccessible areas that are rarely visited. In urban areas, another effective management technique might be avoiding unnecessary wounding during peak periods of fungal mat formation and free-flying nitidulids. Until more is known of the potential for insect transmission, the movement of diseased firewood should also be restricted.

Another alternative for oak wilt control in urban areas is intravascular injection with fungitoxic compounds. Some initial successes have been demon­ strated by injecting diseased live oaks with Lignasan and Arbotect (Lewis, 1977), but results were too variable to recommend treatments. The physical condition of trees and climatic conditions at the time injection are believed to be important variables to be considered when considering injection. Experi­ ments have been initiated to test the use of fungicides as preventatives to natural infection, but there has been insufficient time to judge the efficacy of these treatments.

Summary

Environmental conditions and the occurrence of new hosts strongly influ­ ence the behavior of £. fagacearum and oak wilt in Texas. Control measures developed for different hosts in other states may prove useful to manage the disease on live oaks in the South. However, more information and new approach­ es to oak wilt control are needed to significantly reduce the tremendous losses of live oaks currently taking place in central Texas.

Literature Cited

Appel, D.N., and R.C. Maggio. 1984. Aerial survey for oak wilt incidence at three locations in central Texas. Plant Disease 68:661-664.

Appel, D.N., T. Fox, and C.F. Drees. 1983. The occurrence of oak wilt in Texas. Phytopathology 73:883. (Abstr.).

Appel, D.N., K. Andersen, C.F. Drees, and R.L. Lewis. 1985. Nitidulids as possible vectors of Ceratocysitis fagacearum in Texas. Phytopathology 00:00-00. (Abstract in press)

67 Bowen, K.L., and W. Merrill. 1982. Oak wilt foci related to ridge bearing and aspect in Pennsylvania. Plant Disease 66:137-139.

Epstein, A.H. 1978. Root graft transmission of tree pathogens. Ann. Rev. Phytopathol. 16:181-192.

French, D.W., and W.C. Stienstra. 1980. Oak wilt. Minn. Ag. Ext. Ser. Folder 310, 6 p.

Gibbs, J.N., and D.W. French. 1980. The transmission of oak wilt. North Central For. Exp. Stn., USDA For. Serv. Res. Pap. NC-185, 17 p.

Gillespie, W.H., R.P. True. 1959. Three factors which influence the local spread of oak wilt in five northeastern counties of West Virginia. Plant Dis. Reptr. 43:588-593.

Himelick, E.B., and H.W. Fox. 1961. Experimental studies on control of oak wilt disease. 111. Ag. Exp. Stn. Tech. Bull. 680, 48 p.

Jones, T.W. 1971. A appraisal of oak wilt control programs in Pennsylvania an West Virginia. Northeastern For. Exp. Stn., USDA For. Serv. Res. Pap. NE-204, 15 p.

Jones, T.W., and T.W. Bretz. 1958. Experimental oak wilt control in Missouri. Ms. Agric. Exp. Stn., Res. Bull. 657, 12 p.

Lewis, R. 1977. Oak wilt in central Texas. Proc. Am. Phytopath. Soc. 4:121. (Abstr.)

Lewis, R. 1979. Control of live oak decline in Texas with Lignasan and Arbotect. Proc. Symp. on Systemic Chemical Treatments in Tree Culture, Mich. St., Univ., Kellogg Center for Contin. Educ., East Lansing, 357 p.

Lewis, R.L., and F.L. Oliveria. 1979. Live oak decline in Texas. J. Arb. 11:241-244.

MacDonald, W.L., and D.F. Hindal. 1981. Life cycle and epidemiology of Ceratocystis. Pages 113-114 in: Wilt Dieeases of Plants. Me.E. Mace, A.A. Bell, and C.H. Beckman, eds. Academic Press, N.Y., 640 p.

Menges, E.S., and O.L. Loucks. 1984. Modeling a disease—caused patch distur­ bance: oak wilt in the midwestern United States. Ecology 65:487-498.

Tainter, F.H., and W.D. Gubler. 1973. Natural biological control of oak wilt in Arkansas. Phytopathology 63:1027-1034.

True, R.P., H.L. Barnett, C.K. Dorsey, and J.G. Leach. 1961. Oak wilt in West Virginia. West Virginia University Ag. Exp. St. Bull. 448T. 119 pp.

68 MECHANISMS OF TREE RESISTANCE TO BARK BEETLES; SYNTHESIS AND APPLICATIONS

F.M. Stephen, T.D. Paine, and M.P. Lih Department of Entomology University of Arkansas Fayetteville, Arkansas 72701

During the past six decades there has been a great deal of Interest, speculation, and research into the question of why some bark beetle infesta­ tions grow and others do not. The economic considerations associated with bark beetle—caused losses have generated concern and stimulated research. The biological complexities of bark beetle population dynamics have long fascinated scientists and extensive investigations into factors regulating beetle infesta­ tion growth, e.g. weather, natural enemies, and food have been attempted. Many of the theories generated on this subject relate to the concept of vulnerabil­ ity; i.e. how trees, or stands of trees, may vary in their resistance or susceptibility to attack and colonization by pine bark beetles. Some of the early ideas arose from researchers who observed that less vigorous trees were often the ones killed by bark beetles (Craighead 1928, Person 1928) thus suggesting the importance of individual tree resistance as a factor in the development of bark beetle infestations.

Emerging from these ideas was the concept that forestry practices could influence the probability of outbreaks occurring, and that good silvicultural practices, e.g. thinning to minimize competition; regulation of stand density, age structure, and species competition, should result in fewer bark beetle problems. The tree classification systems of Dunning (1928), Keen (1936, 1943), Salman and Bongberg (1942) and others, arose from observations on the importance of individual tree vigor (i.e. resistance) and how that relates to good forest management.

Development of regionally based hazard rating systems, as a long-term approach to minimizing bark beetle caused timber loss has been a high research priority, particularly in the South. A number of papers, describing at least five different systems, has recently been published (e.g. Hedden et al. 1981, Mason and Bryant 1984). Although many of the systems considered site and stand conditions associated with southern pine beetle infestations, recently there has become an awareness of the association between stand conditions, bark beetle population levels, and likelihood of infestation (Nebeker and Hodges 1983, Paine et. al 1984).

The interactions evident between pines, bark beetles and beetle-vectored fungi, raise numerous and intriguing questions. How does the tree respond to invading organisms; i.e. what physical and chemical mechanisms of resistance does the tree possess to defend itself? How quickly can a tree mobilize its defenses? What impact do these actions have on the invading organisms? What is necessary for the tree to successfully repel or isolate the invading organisms? Conversely, what is required for the invading organisms to overcome the tree's defenses? Does the tree's ability to defend itself change through time? In what manner? Are there obvious physical indicators that can be used to

69 predict which trees, or stands of trees ought to exhibit greater resistance to beetle attack? What is the relationship between the susceptibility of the host tree and the subsequent quality (or suitability) of the tree as a substrate for immature beetles to develop and mature? Do host tree characteristics alone determine the tree's suitability for bark beetle brood development, or is this also regulated by other factors? Can characteristics of the invading beetle population, such as the fungal complex they vector, affect host suitability? Clearly the importance of the host tree and the type of questions raised above must be understood if we are to understand and predict how infestations grow and decline.

Bark beetle outbreaks are generally rare over the life of a stand of trees, and vigorously growing trees are usually resistant to colonization by insects and fungi. However, beetle colonization frequently occurs in susceptible trees (Blanche et al. 1983). Susceptibility can result from a decline in growth or vigor due to senescence (Safranyik et al. 1975), or from stress due to drought (Kalkstein 1976), flooding (Lorio and Hodges 1968), competition for moisture, nutrients, or light (Lorio and Hodges 1968; Ku et al. 1976), root diseases (Cobb et al. 1968), and in the most extreme case, trees that are struck by lightning (Lorio and Bennett 1974).

Lightning struck trees, being completely susceptible to bark beetles, can serve as a reservoir and focus for population build-up and initiate infesta­ tions (Coulson et al. 1983). The risk of an infestation in any area is a function of the physiological condition of a stand and the beetle population level in the area around that stand. A conceptual model relating stand condi­ tions and beetle population levels has been developed and incorporates the concept of a threshold number of beetles required to kill trees of a particular physiological condition (Paine et al. 1984).

The threshold hypothesis, first proposed by Thalenhorst (1958) suggests that the number of beetles necessary to kill conifers is directly related to the physiological condition of the tree. Thus, this threshold is a function of the effectiveness of host tree defenses in repelling or killing colonizing beetles and the number of beetles and their physiological condition. The condition of the beetles may be a function of the suitability of the tree that served as their larval host (Hodges and Lorio 1969; Miller at al. 1968; Cobb et al. 1968) and the microorganisms associated with them (Barras 1973).

Mechanisms Currently Viewed as the Basis for Tree Resistance

Conifer defenses are thought to be generally effective against bark beetles and fungal pathogens. There are two recognized defense systems in conifers, a preformed resin system and an induced hypersensitive response and these are particularly well developed in pines. The resin system, both its physical and chemical properties, has long been seen as the primary form of conifer defense.

Resin System

Sapwood resin is secreted into both horizontal and radial resin ducts by thin walled epithelial cells. Resin ducts are initiated at the cambial ini­ tials and the number of ducts is a function of time of year and plant stress

70 (Werker and Fahn 1969). Cells lining the ducts are also under turgor pressure which exerts pressure on the resin within the central cavity. The resin system and the liquid resin have a number of characteristics that have been associated with host resistance to bark beetles. These characteristics include resin flow rate, total flow, viscosity, crystallization rate (Hodges et al. 1979) oleoresin exudation pressure (Vite and Wood 1961; Lorio and Hodges 1977), and resin composition (Coyne and Lott 1976; Smith 1966). When the ducts are disrupted, resin flows under pressure from both ends of the disrupted duct and from ducts that are connected in a radial plane via a horizontal duct. A tree under stress may have fewer ducts, consequently produce less total resin, and resin may be under less pressure (Fahn 1970).

Individual resin constituents may be toxic to nonadapted bark beetles and to invading fungi (Smith 1963). However, the flow of resin under pressure acts to flush invading beetles and their associated fungi out of the tree. Low rates of flow and low oleoresin pressure have thus been associated with susceptibil­ ity to southern pine beetle (Mason 1971; Lorio and Hodges 1977).

The potential physical action of resin flow from disrupted resin ducts and the potential toxicity of resin composition exists prior to insect coloniza­ tion. The resin system may also be a form of carbon storage since there is a continual turnover of monoterpenes. However, the second, or inducible defense system, is initiated following invasion by the insect or fungi (Berryman 1972''. This system is energy demanding and is initiated only at the sites of infection rather than a systemic response (Raffa and Berryman 1983; Paine 1984). It is, thus, a conservative defense system.

Hypersensitive Response

At the site of beetle attack and fungal inoculation, the infected areas in loblolly pine are initially soaked with resin (Stephen et al. 1983). Part of this resin may be synthesized in situ and part may flow from the sapwood resin ducts into the phloem duct system. The invaded tissue is surrounded by callus cells originating from the cambium (Wong and Berryman 1977). This resin soaked zone dies and is surrounded by newly formed periderm (Shrimpton 1978). The hypersensitive reaction has been observed in response to colonizing beetles or inoculated fungi (Reid et al. 1967; Shrimpton 1978; Paine 1981; Stephen et al. 1983). Resin constituents of the hypersensitive response of lodgepole pine to D. ponderosae colonization have been demonstrated to be fungistatic (Shrimpton 1973; Shrimpton and Whitney 1979). However, this fungistatic property has not been demonstrated in any other system examined to date (Paine 1984).

The size of the lesion produced in response to infection has been used to identify lodgepole pines susceptible to D. ponderosae (Safranyik et al. 1975). The accuracy of this hazard rating system has been questioned (Peterman 1977), but recent work on loblolly pine suggests that it can be a sensitive indicator of tree stress and site conditions (Stephen et al. 1983).

Associated Fungi

Throughout the bark beetle literature there are implicit or explicit assumptions that fungi associated with the colonizing beetles are responsible for tree death (Craighead 1928; Graham 1967; Wood 1972). Early workers demon­ strated in southern pines that tunneling action of the beetle alone was insuf—

71 ficient to account for the rapid decline in tree vigor that was observed (Nelson and Beal 1929; Nelson 1934; Caird 1935; Bramble and Holst 1940) and that fungi associated with the southern pine beetle could kill these trees in the absence of the insect (Hetrick 1949). The mode of action of tree death was by stopping water conduction through vascular plugging, aspiration, or introduc­ tion of toxins (Nelson 1934; Basham 1970; Hemingway et al. 1977).

The primary tree-killing Dendroctonus species are actually an association of tree invading organisms. The beetles are closely associated with specific fungi; many have specialized cuticular structures, mycangia, that foster the growth of these fungi and facilitate their transport. Females, the initial colonizing sex, have prothoracic mycangia (Barras and Perry 1972; Whitney and Cobb 1972). The fungi within the mycangia grow and are inoculated into newly colonized trees (Barras and Perry 1972; Paine and Birch 1983).

The fungi associated with Dendroctonus spp. are also highly specialized in growth form. Dendroctonus frontalis is associated with two mycangial fungi, an unnamed basidiomycete and the non-staining Ceratocystis minor var. barrasii (Bayras and Perry 1972). Also I), frontalis is associated with a staining form of the mycangial Ceratocystis, _C. minor, which is normally found on the exter­ nal surface of the insect's body and is often vectored by phoretic mites living in close association with the beetle (Bridges and Moser 1983). The external staining form may be ancestral to the specialized mycangial forms and has long been implicated as the agent of beetle induced tree mortality, although recent observations (Bridges 1985) indicate that infestations may develop that contain the fungi other than the blue-staining form.

Inoculation of large quantities of fungi through many infection courts could be achieved by the beetle as a result of its chemical communication system. Females that initially colonize a new tree release pheromones that result in aggregation and a mass attack by beetles on the new host (Payne 1980). The action of the beetles in excavating new galleries and the inocula­ tion of pathogenic fungi overwhelms the host defenses and insures rapid death of the new host. Raffa and Berryman (1983) have suggested that the females will continue to produce pheromone only as long as the host is actively defend­ ing itself. Once the defense mechanisms cease functioning the females stop pheromone production, thus regulating the population density so that the tree is killed but competition among progeny is limited.

New Hypotheses on Tree Resistance

The recent interest in insect/fungal/host-tree interactions has resulted in the proposal of several hypotheses related to tree resistance mechanisms. Hodges et al. (1985), drawing on the published literature and their own re­ search suggest that the first line of defense is the resin system.. .with high resin flow potentially imparting resistance in one of three ways: resin toxicity, physical "pitching—out" of attacking beetles, and/or prevention of fungal inoculation. They hypothesize that successful attack requires inocula­ tion of fungi which subsequently produce toxins, making the tree more suscepti­ ble to additional bark beetle attacks until resistance is overcome. This hypothesis is expanded in the form of a conceptual model involving trees of differing levels of resistance and varying beetle population levels. Lorio (1985) also considers the primary defense to be the resin system, and hypothe­ sizes the resin system's effectiveness to be a function of growth

72 differentiation processes, which implies that resin duct formation and resin production occurs at those times of the year when conditions for growth are not favorable. Thus, for example, in spring when growth is maximal, less resin flow will be expected and attacks may have more chance of success. The oppo­ site may be anticipated in the summer, when greater resin flow and resistance are expected. Mattson and Hain (1985), also conclude from the published literature that there are two separate defense systems, with the resin system being more important in southern pines, but not necessarily so in some of the western species. Sharpe and Wu (1985) incorporating information from all of the current research plus the existing literature, have developed an integrated host susceptibility model that they suggest contains the essential components of tree susceptibility to bark beetles without excessive mathematical complex­ ity. Paine, Stephen and Cates (1985) are examining the ecological chemistry of loblolly pine resin and phloem, in an attempt to understand the relationships involved with the resin system and hypersensitive response and how they may relate to southern pine beetle population dynamics. Some of their ideas are discussed in more detail later in this paper.

Impact on Beetle Populations

It is unclear what impact host defenses (preformed and induced) have against the initial colonizing parent adults and what these impacts might have on the population dynamics of the beetles. It is also unclear what the role of host defenses and tree suitability might be on developing progeny. The role of varying host defenses (resistant to susceptible) and host quality (suitability) on southern pine beetle population dynamics may be related to the impact of the tree on the fungi associated with the insect. It is thus important to under­ stand the response of the tree to these fungi, growth of the fungi while the tree is actively defending itself, and the reproductive success of the insect with different fungal associations.

Arkansas Based Research on Host/Fungi/SPB Interations

The underlying objective of the research efforts centered at the University of Arkansas has been to relate the host defenses of loblolly pine to the population dynamics of the southern pine beetle. That is, to understand the relationship between host tree condition (tree stress or vigor) and the risk of a bark beetle spot spreading once an infestation has started. There are a number of factors that can be related to the ability of a host tree to defend itself and these were examined through a series of separate objectives.

Phenology and Rate of Response

New beetle infestations are frequently initiated in the spring of the year and decline during the winter months. This pattern can be partially related to the effects of temperature on insect development, and to the availability of susceptible hosts resulting from lightning strikes during the spring (Coulson et al. 1983). Lorio and Hodges (1985) hypothesized that growth differentia­ tion, relating to resin duct formation in late versus earlywood, may play a key role in bark beetle infestation patterns. We have also established that healthy trees show a seasonal pattern in the expression of their induced defenses (Stephen and Paine 1985). Except during the coldest months of the year, trees growing on the same site respond to infection by producing lesions that are the

73 same length. During the months of November, December and January these lesions are significantly smaller than during the rest of the year, and during September they are significantly longer.

The ultimate size of the response, however, may not be as critical to successful defense as the rate of lesion formation. Trees respond with the same size lesions during both the spring and summer, but the rate of the response is significantly different. During the summer months, maximum lesion size is achieved during the first week following inoculation. In the spring, however, lesions are not fully developed until three weeks after inoculation. This suggests that the tree may be more vulnerable to prolonged attacks during the spring, and conversely implies that beetles attacking at a slower rate during the summer would induce a quick response from the tree and would more likely be killed.

An additional study was conducted to examine the rate of response on a much finer scale. Trees inoculated in June showed little response to infection with any combination of fungi during the first 60 hours but then responded rapidly during the following 60 hours, achieving almost maximum size during that time interval. This indicates that a rapid colonization phase by the beetle will overcome the tree before the induced system can be fully initiated. However, females attacking at a low density over a prolonged period must deal with the induced system that responds rapidly after an initial lag period.

Other insights were obtained from these phenology studies. The first and most important result came from comparing the response of the tree to the combinations of the three fungi associated with the southern pine beetle. Preliminary studies suggest that trees respond very differently to the three fungi associated with the southern pine beetle. Although the pattern of lesion formation is very similar for all fungi (Stephen et al. unpublished) the size of the responses is significantly different. In fact, sterile wounding induces responses that are not significantly different from those seen in response to either mycangial fungus, but the response to the nonmycangial form of C. minor is significantly larger (unpublished data). This suggests that the mycangial fungi are more highly adapted as pathogenic fungi than the blue-staining form that has consistently been suggested as the fungus responsible for tree death. The growth rates are not available as yet for the mycangial fungi, but the staining form of C. minor grows as much as 3 cm from the point of infection in the first 48 hours following inoculation and up to 5 cm within 6 days. How­ ever, the fungus is confined completely within the fully formed lesion after three weeks (Paine et al. unpublished).

Hypersensitive Response as an Indicator of Resistance

The induced system as one aspect of host tree defenses has been used to characterize host vigor in other parts of North America (Safranyik et al.1975, Peterman 1977). If the induced system is to be used as a vigor index for loblolly pine, it is important to determine if the response is graded and related to the amount of inoculum, or whether the size is a characteristic of the tree, and as such only a single size lesion will be produced for a tree with a particular set of characteristics. The size of the response does not seem to be dosage-dependent. The same size responses were produced following inoculation with doses of fungi varying by a factor of eight even if the size of the wound was not constant. Fungal infections induced significantly longer

74 lesions than did sterile wounding on killed fungi at all but one dosage level (Paine and Stephen, unpublished)• In another experiment, there were no differ** ences in the size of a control response in an inoculation pattern varying in density from 1 to 32 inoculation points per ten square dm (Paine and Stephen, unpublished). Equal dosages of fungi produced significantly different lesion sizes in trees of various diameter classes located on the same site. These results suggest that a tree responds to infection independently of the amount of inoculum but rather the tree response may be a function of initial tree vigor. It follows that inoculations of trees within a stand can be compared and that the technique may be suitable to establish a vigor index.

The inoculation of C « minor could be used to distinguish among levels of tree stress. In an even-age stand, smaller trees, assumed to be stressed by competition, produced smaller lesions in response to infection than did domi­ nant or codominant trees (Stephen et al. 1983). Also, trees growing on a poorly drained site produced smaller lesions than did the same diameter trees growing on a site with better drainage (Paine and Stephen, unpublished). The size of the response did not vary with the height of the inoculation, suggesting that the site of initial infestation by the beetle is not a function of variation of host defenses (Paine and Stephen, unpublished). There were also no differences in the size of response between trees that had been inoculated previously compared to trees that were initially inoculated at the same time of year (Paine et al. 1985; Paine and Stephen, unpublished). This suggests that the induced defense system is not sensitized by previous infection or beetle activity.

In addition to analyzing for differences in size of lesions among trees of different stress levels and between plots, work done in conjunction with Dr. T. E. Nebeker at Mississippi State University has indicated differences in chemi­ cal composition of the lesion. Trees growing on the ridge plot had significant­ ly lower composition (by %) in myrcene and three unknown monoterpenes. How­ ever, lesions produced by trees growing on the ridges had significantly higher levels of B-phellandrene. There were no differences in composition of lesions between diameter classes on the ridge and only a slight difference in B-phell­ andrene between diameter classes of trees growing in the bottom plots. There were also significant differences in the composition of liquid resin and the resin found within the lesions for six of nine monoterpenes common to both, as well as two compounds found in the lesions and not found in the liquid or preformed resin (unpublished data).

Trees that are vigorously growing produce larger lesions than do trees that are more stressed. However, it is unclear whether the induced system of tree defense has an impact on colonizing adults and their subsequent reproductive success. Field observations support the assumption that the tree responds to attacking females in the same manner as to the artificial inoculation and that attacking adults can be killed. Laboratory studies also demonstrate the impact of these defenses. There was a higher degree of mortality of adults forced to bore in hypersensitive reaction tissue of trees that had been inoculated with C. minor six weeks previously, had completed the reaction to those inoculations, and were then felled, when compared to control logs that had not been treated. This is probably due to the deposition of resins within the reaction zones and subsequent flow of those resins into the galleries. This experiment simulates a gradual attack process, where attacking adults may encounter exist- ing lesions. Similarly, the number of progeny

75 emerging from logs where adults constructed galleries in hypersensitive tissue was only 44% of the number emerging from the control tissue. These results are preliminary, and analyses are underway to determine such factors as whether less eggs were laid per adult female, or whether the developing progeny suffered a higher rate of mortality. Studies using wild populations of beetles in natural stands are also being analyzed, but in the highly controlled yet somewhat artificial laboratory studies the induced system appears to have a strong influence on attacking adult and reproductive success.

One Interdependent Defense System?

Despite the convenience for discussion of dividing host defenses into two systems, they are in all probability not separate and distinct. Rather, they are highly interdependent. There does not seem to be any resin in undamaged phloem (Cates et al. unpublished data), yet resin appears very quickly follow­ ing injury. The appearance is too rapid to be the result of synthesis, so it is probably a result of the opening of the horizontal resin ducts at the cambium and movement of the xylem resin into the phloem. This means that both the preformed and induced systems are a single system. The impact of both on invading insects or infecting pathogens is highly related to plant nutritional status, water relations, physiological condition, and competition. Overall site and stand conditions and time of year directly influence stand hazard which can be very dynamic. Stand risk or the probability of an infestation starting and growing can thus be dynamic, changing with the time of year (i.e. seasonal phenology) as well as changing as a result of different levels of insect populations. It also may mean that a given stand of trees may be capable of producing more beetles if the trees are colonized during one particular time of year (i.e. the spring) when trees may be less resistant than if they are colonized later in the year when the trees are more resistant. These differ­ ences may be important considerations to be incorporated into simulation models of southern pine beetle population dynamics.

Application of Tree Resistance Knowledge

As our understanding of the mechanisms of tree resistance to insect and fungal invasion increases, and we associate this with impact on populations of southern pine beetle (Dendroctonus frontalis Zimm.), we can apply this knowl­ edge through various pathways (Stephen et al. 1983). The approach on which we are concentrating is to refine a computer-based model which was designed to predict growth of southern pine beetle infestations and corresponding tree mortality expected over relatively short periods of time (e.g. 1-3 months) (Hines et al. 1980, Lih and Stephen 1983). This model has been developed as a tool for decision-making in forest pest management. A first priority in the design and construction of the model has been the requirement that it be user-oriented. The information needed to access and run the model has been kept simple, in order to encourage acceptance by the user community. The internal structure of the model is, however, intricate as it must be in order to accurately represent the biological complexity of southern pine beetle population growth in diverse pine ecosystems. Temperature controls the activity and development of beetle life forms. Mortality rates reflect the combined influence of natural enemies, competitors, host suitability, tempera­ ture, and forest stand conditions.

76 The model was pilot tested by forest pest management specialists (Nettleton and Conner 1984) and found to be a useful and accurate means for predicting beetle population growth and tree mortality under specific site and stand conditions. However, the predictions were not sufficiently realistic when site, stand, or beetle population conditions differed considerably from those which where originally used in formulating the model and establishing its parameter values. Although tree and stand conditions did play a role in setting beetle mortality rates in the early versions of the model, their impact was inferred by our intuitive understanding of the interactions between stand variables and specific beetle population parameters. We thus determined that the model needed to be more sensitive to varying stand conditions if it was to be useful over the variety of stand types and beetle population levels encoun­ tered southwide.

Research has thus been conducted to determine whether a functional rela­ tionship could be established between tree and stand conditions, beetle attack density, egg density, mortality of eggs, mortality of larvae and pupae, and mortality of brood adults (Lih and Stephen 1985). Regression equations were developed for each of these population parameters. These predictive equations were incorporated into the simulation model, and test runs made on seventy infestations from which data were available. The model's performance was considerably improved by incorporating tree- and stand-dependent beetle density estimates and mortality rates. The new model's predictions are, on the aver­ age, substantially closer to actual infestation growth data than were those of the early version. This improvement is verified when predictions are analyzed based on subgroups of data indicating time of year, initial infestation size, and area-wide population levels.

These improvements have made the model more responsive to tree- and stand conditions. Pilot tests, using data from East Texas to Georgia, encompassing several years and representing varying population levels substantiate this. As additional knowledge about the mechanisms of tree resistance and the interac­ tions between trees, beetles and their associated fungi becomes available, it will be applied toward further improvement of the simulation model. These refinements will also enhance the model's use as a mechanism for testing theories and gaining more basic understanding of the southern pine beetle/- fungi/host tree ecosystem.

Acknowledgements

This study was supported in part by the Integrated Pest Management Research, Development and Applications Program, Pineville, LA USFS Cooperative Agreement 19-81-61, and was published with the approval of the director of the Arkansas Agricultural Experiment Station.

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82 RECENT ADVANCES IN CONTROL OF BROWN SPOT IN LONGLEAF PINE

Albert G. Kais Principal Plant Pathologist USDA Forest Service Southern Forest Experiment Station Gulfport, Mississippi 39505

Longleaf pine (Pinus palustris Mill.) is a highly desired tree species for lumber and poles, is exceptionally resistant to fire, grows well on dry coastal plain sites, and is not usually attacked by fusiform rust. However, it has been difficult to regenerate because of problems in nursery production and outplanting, possession of an inherent trait of delayed height growth ("grass stage"), and severe damage caused by brown-spot needle blight.

This blight, caused by Scirrhia acicola (Deam.) Siggers, defoliates seedlings, reduces seedling vigor, and causes mortality. Continual defoliation with subsequent reduction of seedling vigor delays the initiation of height growth. After longleaf seedlings begin height growth, disease effects are minimal.

Historically, fungicides have been considered an important alternative for control gfjbrown-spot needle blight on longleaf pine. Bordeaux mixture, ferbam (Fermate ) , and other protectant fungicides have been effective in nurseries and seed orchards but cannot be economically used in forest plantings (Phelps et al. 19^8, Wakeley 1954). Benomyl (Bgnlate ), gopper hydroxide, Captafol (Fifolatan ), and Clorothanlonil (Daconil or Bravo ) have also been found to be effective for brown-spot control (Kais 1975). In these reports both sur­ vival and growth have been significantly improved following disease control with fungicides.

Early initiation of height growth also reduces the effects of brown-spot needle blight. Some of the crucial factors affecting height growth are: (1) seedling quality, (2) weed and grass competition, and (3) nutrition. Seedling quality depends on seed source (Derr and Melder 1970, Snyder and Derr 1972) or on nursery seedbed density (Scarbrough and Allen 1954). Competition in the field has been controlled with scalping, disking, or furrowing (Bruce 1958, Derr 1957, Mann 1969, Smith and Schmidtling 1970). Nutrition supplied by application of NPK in the absence of competition also stimulated early and total growth of longleaf pine (Allen and Maki 1955, Lewis 1977, Smith and Schmidtling 1970).

Varying levels of disease resistance have been reported for individual longleaf trees (Boyer 1972, Derr and Melder 1970, Snyder and Derr 1972), between young and old needles on the same plant (Kais 1977, Snow 1961), and among geographic sources (Henry and Wells 1967). The inheritance of outstand­ ing resistance in the FI progeny of individual longleaf pine (Bey and Snyder 1978, Derr and Melder 1970) and the gain of resistance by selection (Snyder and Derr 1972) suggest future practical control of the disease.

Trade or proprietary names are included for information purposes only and do not imply any endorsement by the Forest Service or the USDA.

83 Genetic manipulation can result in increased growth as well as increased survival and resistance to brown-spot needle blight (Snyder et al. 1977). This paper concurrently summarizes recent advances in both the control of brown-spot needle blight and in the stimulation of rapid height growth of longleaf pine seedlings. These advances will be treated under three general topics: (1) disease control by a systemic fungicide, (2) tree growth stimulation by cul­ tural practices, and (3) disease control and growth stimulation through im­ proved planting stock.

Disease control by systemic fungicide.— Benomyl, following its initial report as a control brown-spot needle blight (Kais 1975), has been extensively tested and found to be a very effective systemic fungicide in establishing longleaf pine plantations. This material, primarily used as a root dip treat­ ment, not only provided excellent disease control but also improved survival and stimulated early height growth of longleaf pine seedlings.

A 5% a.i. benomyl/kaolin mixture was found to be the optimal treatment for disease control over the entire range of longleaf pine in the southern United States (Kais et al. in press). Root systems of longleaf pine were wetted and coated with the benomy1-clay mixture just prior to outplanting. This treatment effectively controlled the disease during the critical 3-year period following outplanting. It also indirectly promoted better survival rates, greater stem lengths, and a higher percentage of seedlings that initiated early height growth.

An evaluation of seedling nursery storage time following benomyl treatment indicated that the length of cold storage before planting significantly affect­ ed survival and growth of seedlings while the benomyl treatment primarily affected the incidence of brown-spot disease (Kais and Barnett 1984). A later report indicated that benomyl applied to seedling roots either prior to nursery storage or at the time of outplanting equally reduced brown-spot infection during the first year in the field (Cordell et al. in press). Of four storage media tested (clay slurry, peat moss, hydromulch, and Terrasorb), best survival occurred with seedlings stored in either the clay slurry or peat moss for periods of 6 weeks or less. Benomyl application in the nursery would eliminate fungicidal treatment by the grower at planting time.

Benomyl has been registered for use as a seedling root-dip treatment prior to packing at the nursery or prior to planting at the forestation site to control brown-spot needle blight on longleaf pine. Specific information is given in the Agricultural Bulletin issued by E.I. Du Pont De Nemours & co., dated November 16, 1984, and entitled, Supplemental Labeling, EPA Reg. 352-354, Benlate Fungicide for Control of Brown-Spot Needle Blight on Longleaf Pine.

Tree growth stimulation by cultural practices.— Theoretically, cultural practices that stimulate early height growth of longleaf pine seedlings indi­ rectly control brown-spot disease, because longleaf pine seedlings become resistant to the disease when they attain the height growth stage. Growth can be significantly improved with competition control, by the application of fertilizers, and by the use of ectomycorrhizal seedlings. These cultural practices are most beneficial when the disease is controlled or eliminated.

Recent studies have all confirmed that competing vegetation can be effec­ tively controlled for a 2-year period by a shallow scalping of the planting

84 site. Although scalping by itself provides early weed control, the combination of scalping followed by herbicide application as a postemergence weed killer can be even more effective. Two herbicides, Velpar and Goal have both provided excellent weed and grass control during the first growing season and somewhat less control the second growing season. Both materials were selective in their action, being specifically toxic to weeds and grasses but not toxic to the longleaf pine seedlings. The early control of herbaceous competition reduces the length of time longleaf pine seedlings are in the disease-vulnerable grass stage (Nelson et al. 1982).

Nutritional supplements to longleaf pine seedlings growing in the field have stimulated and subsequently reduced the grass stage period. This was most apparent with low levels of brgwn-spot infection. Growth response were further increased if a herbicide (Goal ) was applied with a fertilizer (Table 1). With the combined treatments, more than 90% of the seedlings initiated height growth during the second year.

Table 1. Effect of fertilizer on growth responses of longleaf pine after 2 years in the field.

Plant response +F+G -F+G +F-G -F-G

Infection (%) 14.2 20.1 14.8 20.5

Survival (%) 93.4 92.6 94.6 93.0

Stem length (cm) 38.6 17.2 29.5 14.9

Height growth (%) 93.5 64.6 86.0 64.4

F = Fertilizer (13-13-13); G = Goal herbicide

Mycorrhizae can stimulate longleaf pine growth. Ectomycorrhizae of Pisolithus tinctorius (Pers.) Coker and Couch (Pt) were originally reported to stimulate the growth and quality of longleaf pine seedlings in nursery beds (Marx 1977). This ectomycorrhizal development by P. tinctorius on longleaf pine seedlings with Pt ectomycorrhizae increased survival, height, and stem diameter (Hatchell 1981). Although Pt ectomycorrhizae and benomyl could each stimulate growth and survival of longleaf pine seedlings, combining these two factors resulted in maximum plant responses (Kais et al. 1981). In a Southwide study it was noted the Pt seedlings had higher survival rates than Pt-free seedlings: 21% more in Louisiana, 24% more in Mississippi, 6% more in Alabama, and 22% more in Florida (Kais et al. 1985).

Seedlings inoculated with Pt ectomycorrhizae inoculum in the nursery seedbed generally had superior root systems and larger stem diameters. Over­ all, they were more vigorous. However, it should be reiterated that the Pt effect on subsequent growth of outplanted seedlings was most pronounced with control of brown spot.

85 Disease control and growth stimulation through improved seedling quality.— Seedling quality is important for the successful regeneration of longleaf pine. Quality seedlings are produced by three different methods: (1) by specific cultural practices during growth in nursery beds, (2) by control pollinations involving superior longleaf pine families, and (3) by species hybridization.

Top quality nursery stock can be growth by using low seedbed densities. Longleaf pine seedlings grown at a seedbed density of 10-15 seedlings per sq. ft. had greater stem lengths and initiated height growth sooner (Table 2). This density range results in the production of seedlings having diameters of about 0.5 in, which is optimal for growth and survival in the field following outplanting.

Table 2. Effect of seedling quality on growth responses during the 2nd through the 4th years in the field following outplanting.

Response and seedbed density 2nd year 3rd year 4th year

Stem length

10-15 sq. ft. 19.5 69.3 137.6 25-30 sq. ft. 12.1 53.6 113.4

Height Growth ---- % ------

10-15 sq. ft. 66.4 95.7 98.5 25-30 sq. ft. 46.1 89.5 97.3

Control pollinations have been extremely successful in producing superior families that have the combined characteristics of fast growth capability and disease resistance. Actual disease development in the field has been de­ termined for open—pollinated families both resistance and susceptible to brown spot (Griggs and Schmidt, in press). It was determined that mixing resistant and susceptible open—pollinated families of longleaf pine did not appear to be a useful strategy for slowing brown-spot needle blight epidemic in time or space. Disease resistance was expressed primarily as a delay in the onset of needle dieback.

The relationship of brown-spot infection to survival and growth of 29 different families of control pollinations varying in disease resistance and height growth has been determined (Kais and Griggs, in press). In this study, benomyl was used to control disease so that inherent resistance could be evaluated for response to brown-spot infection. There was a negative corre­ lation between brown-spot infection and either survival percent or height growth. Survival and growth rates were both significantly increased with the use of a benomyl root-dip treatment (Table 3). After 2 years in the field, benomyl-treated seedlings had approximately 1/4 of the infection, approximately 15% more survival, twice the stem length, and twice as many seedlings in height

86 Table 3. Plant responses of genetically Improved families with and without brown-spot needle blight control after 2 years in the field.

Plant responses Benomyl treatment Untreated

Infection (%) 16.4 67.6 6.4 - 38.I1 52.8 - 88.3

Survival (%) 88.7 73.9 59.9 - 1000.0 21.7 - 100.0

Stem length (cm) 17.9 9.3 7.3 - 38.7 4.2 - 19.4

Height Growth (%) 50.5 22.1 10.5 - 83.6 0.0 - 57.7

Range of means for the 29 longleaf pine families tested. growth as their untreated counterparts. Resistant longleaf pine families could initiate early height growth even when they were severely infected with brown spot.

Species hybridization presents the third technique for developing superior planting stock. The objective is to produce a hybrid lacking the grass stage and having some resistance to the disease. The performance of one such hybrid is detailed in Table 4. This particular hybrid, a cross consisting of 1/4 loblolly x 3/4 longleaf pine, had been outplanted following treatment with benomyl or clay. The hybrid had better survival rates, less infection, greater stem lengths, and much greater number of seedlings in height growth than their paired longleaf pine seedlings. The hybrid seedlings began stem growth immedi­ ately and were not quite as susceptible to brown-spot disease. For both pine species, significant gains were achieved in survival and growth by disease control.

Summary

1. There is an inverse relationship of brown-spot needle blight to survival and subsequent growth of longleaf pine. Therefore, disease control is required in high-hazard areas.

2. A root-dip treatment with benomyl is the most effective and practical method for controlling the disease on longleaf pine seedlings. It has been registered for application either during the nursery operation and/or at the time of field planting.

3. The effects of brown-spot infection are significantly reduced by the rapid growth of longleaf pine. Longleaf pine becomes resistant with initiation of height growth.

87 Table 4. Comparison of plant responses of hybrid and longleaf pine with and without disease control after 2 years in the field.

Hybrid^ Longleaf Response Benomyl Clay Benomyl Clay

Infection (X) 14.7 68.0 31.9 73.8

Survival (%) 93.4 66.2 71.3 51.8

Stem length (cm) 36.0 11.8 5.7 4.0

Height Growth (%) 89.1 31.9 10.4 1.0

Hybrid = 1/4 loblolly x 3/4 longleaf pine.

4. Rapid height growth of longleaf pine is stimulated by:

a. Use of superior planting stock such as quality-grown nursery stock, genetically improved families, and hybrids.

b. Control of competing vegetation by scalping and/or the use of herbicides.

c. Effective disease control by the use of benomyl.

d. Application of fertilizer in conjunction with disease and competition control.

e. Use of ectomycorrhizal (Pt) seedlings with disease control.

Each grower should determine the specific strategy he must use for the successful growth of longleaf pine depending upon the nature and characteris­ tics of his planting site. In any case he should use quality planting stock. The use of benomyl, herbicides, fertilizer, or ectomycorrhizae will depend upon such site factors as the amount of disease present, the amount of competition existing, site index, and actual costs of materials.

Literature Cited

Allen, R.M., and T.E. Maki. 1955. Response of longleaf pine seedlings to soils and fertilizers. Soil Sci. 79:359-362.

Bey, C.F., and E.Bayne Snyder. 1978. Genetic gains through testing and crossing longleaf pine plus trees. USDA South. For. Exp. Stn. Res. Note SO-241, 5 p.

88 Boyer, W.D. 1972. Brown-spot resistance in natural stands of longleaf pine seedlings. USDA South. For. Exp. Stn. Res. Note 142, 4 p.

Bruce, D. 1958. Effect of low compettition on longleaf pine seedling growth. Proc. Soc. of Amer. For., Salt Lake City, Utah. 151-153.

Cordell, C.E., A.G. Kais, and C.E. Affeltranger (In press). Effects of benomyl root storage treatments on longleaf pine seedling survival and brown-spot disease incidence. Proc. South. Nurserymen's Conf. Asheville, N.C. 1984.

Derr, H.J. 1957. Effects of site treatment, fertilization, and brown spot control on planted longleaf pine. J.For. 55:364-367.

Derr, H.J., and T.W. Melder. 1970. Brown-spot resistance in longleaf pine. For. Sci. 16:2.04-209.

Griggs, M.M., and R.A. Schmidt (In press). Disease progress of Scirrhia acicola in single and mixed family plantings of resistant and susceptible longleaf pine.

Hatchell, G.E. 1981. Response of longleaf, sand, and loblolly pine to Pisolithus tinctorius ectomycorrhizae and to soil amendments applied at outplanting in the Carolina sandhills. Program and Abstracts, 5th North American Conference on Mycorrhizae, August 16-21, 1981, Quebec, Canada, p. 75.

Henry, B.W., and 0.0. Wells. 1967. Variation in brown-spot infection of longleaf pine from several geographic sources. USDA South. For. Expt. Sta. Res. Note S0-52, 4 p.

Kais, A.G. 1975. Fungicidal control of Scirrhia acicola on longleaf pine seedlings. USDA Plant Dis. Reporter 59:686-688.

Kais, A.G. 1977. Influence of needle age and inoculum spore density on susceptibility of longleaf pine to Scirrhia Acicola. Phytopathology 67:686-688.

Kais, A.G., and J.P. Barnett. 1984. Longleaf pine growth following storage and benomyl root-dip treatment. USDA Tree Planter's Notes 35:30-33.

Kais, A.G., C.E. Cordell, and C.E. Affeltranger. 1985. Increased survival of longleaf pine with Pisolithus tinctorius and benomyl. IN Proc. 6th North American Conference in Mycorrhizae, June 25-29, 1984, Bend, Oregon, p. 222.

Kais, A.G., and M.M. Grigs (In press). Control of brown-spot needle blight infection on longleaf pine through benomyl treatment and breeding.

Kais, A.G., C.E. Cordell, and C.E. Affeltranger (In Press). Benomyl root treatment controls brown-spot needle blight on longleaf pine in the southern United states.

Lewis, C.E. 1977. Longleaf pine responds through age 15 to early fertili­ zation. USDA Southeastern For. Exp. Sta. Res. Note SE-239, 7 p.

89 Mann, W.F., Jr. 1969. At last—Longleaf pine can be planted successfully. For. Farmer 28:6, 7, 18, 19.

Marx, D.H. 1977. The effects of different rates of vegetative inoculum of pisolithus tinctorius on ectomycorrhizal development and growth of long­ leaf and shortleaf pines. Abstract, 3rd North American Conference on Mycorrhizae, August 23-25, 1977, AThens, GA. p. 21.

Nelson, L.R., S.A. Knowe, and D.H. Gjerstad. 1982. Use of effective herbicide treatments for artifical regeneration of longleaf pine. Ga. For. Res. Paper 40, Res. Div. Georgia For. Comm., 7 p.

Pawuk, W.H., J.L. Ruehle, and D.H. Marx. 1980. Fungicide drenches affect ectomycorrhizal development of container-grown Pinus palustris seedlings. Can. J. of For. Res. 10:61-64.

Phelps, W.R., A.G. Kais, and T.H. Nicholls. 1978. Brown-spot needle blight of pines. USDA For. Ser. For. Ins. and Dis. Leafl. 44, 8 p.

Scarbrough, N.M., and R.M. Allen. 1954. Better longleaf seedlings from low-density nursery beds. USDA For. Serv. Tree Planter's Notes 18:29-32.

Smith, L.F., and R.C. Schmidtling. 1970. Cultivation and fertilization speed early growth of planted southern pines. USDA For. Serv. Tree Planters' Notes 21:1-3.

Snow, G.A. 1961. Artificial inoculation of longleaf pine with Scirrhia acicola. Phytopathology 51:186-188.

Snyder, E. Bayne, and H.J. Derr. 1972. Breeding longleaf pines for resistance to brown spot needle blight. Phytopathology 62:325-329.

Snyder, E. Bayne, R.J. Dinus, and H.J. Derr. 1977. Genetics of longleaf pine. USDA For. Serv. Res. Paper WO-33, 24 p.

Wakeley, P.C. 1954. Planting the southern pines. USDA For. Serv. Agric. Monog. No. 18, 233 p.

90 SESSION III

Moderator:

Dr. Fred Jewell Professor Louisiana Tech University Ruston, LA

91 UTILIZATION OF PHEROMONES IN FOREST PEST MANAGEMENT

C. Wayne Berisford Department of Entomology University of Georgia Athens, GA 30602

Gary L. DeBarr USDA Forest Service Southeastern Forest Experiment Station Athens, GA 30602

Thomas L . Payne Department of Entomology Texas A&M University College Station, TX 77843

Specific Uses of Pheromones in Southern Forest Management

' In spite of the substantial number of pheromone studies, only in a few cases have management techniques which include pheromones been accepted or sufficiently tested to become an integral part of forest management in the near future. Representative cases are described below, some of which, although apparently successful, have not been generally adopted.

Southern Pine Beetle

Several attempts have been made to utilize SPB behavioral chemicals in some manner for control. Vite' (1970) described a potential control technique in which un^tacked trees were treated with the herbicide cacodylic acid (Silvisar 510 ) to make the inner bark unsuitable for SPB brood development and baited with the beetle attractant frontalure (frontalin: a pinene). Additional tests of the technique by Ollieu (1969) and Copony and Morris (1972) suggested that it might be a viable control technique. However, Coulson et al. (1975) found that the effect of the cacodylic acid was not uniform and that SPB broods often had a high survival rate in parts of the trees. The technique has not been adopted as a usable control method. Payne et al. (1977) attempted to use antiaggregation pheromones (verbenone and endobrevicomin) to prevent SPB landing on trees. The technique successfully reduced, but did not prevent attacks by SPBs (Richerson and Payne 1979) and SPBs were competitively replaced by Ips avulsus (Eichhoff). A technique for suppression of individual SPB spots (Richerson et al. 1980) has proved successful in a number of field trials (Payne et al. 1985). The technique uses frontalure to strategically bait the centers of infestations to attract emerging beetles to previously infested pines and hardwoods until natural pheromones are no longer produced by SPBs in trees under attack at the head of the spot. In Georgia, the technique has effectively shut down 80% of the SPB spots treated. This success rate is equal to or better than other control tactics such as cut and leave and salvage. A publication on spot selection and treatment protocol is being prepared for the 1986 season.

92 Pine Tip Moths

Sex pheromone components for the Nantucket pine tip moth Rhyaclonla frustrana (Comstock) have been used In control attempts to confuse males and prevent mating by permeating the air with pheromones (Berisford and Hedden, 1978). This study, and several subsequent studies, showed that by applying 8-10 gms of pheromone per acre, male response to live females in traps and to pheromone traps could be totally inhibited, but consistent damage reduction was not achieved. Some additional studies showed substantial damage reduction, but others showed no reduction or even apparent increases in a few cases (C.W. Berisford, S.A. Cade, R.L. Hedden, L.H. Kudon, unpublished).

Synthetic sex pheromones of the Nantucket pine tip moth, however, have been successfully exploited in a system to precisely time applications of insecticides. Once the optimum times for insecticide applications were esta­ blished relative to the tip moth life cycle (Berisford et al. 1984), models were developed to predict that optimum time (Gargiullo et al. 1983, 1985). The prediction models use pheromone traps to detect the first male emergence of a given tip moth generation to establish a fixpoint. From that fixpoint degree- days are accumulated above the thresholds for moth activity and egg development thresholds to predict the occurrence of the most vulnerable life stages. For example, to maximize tip moth control by using dimethoate (Cygon formulation), applications would be made at ca. 75% egg hatch or 263 degree days Celsius (474) degree days Fahrenheit) for the first tip moth generation (Gargiullo et al. 1985). This model provides very effective tip moth control and reduces costs and environmental contamination by decreasing the numbers of annual spray applications.

Seed and Cone Insects

Pheromone traps are used regularly in some pine seed orchards to monitor for the presence of coneworms, Dioryctria spp., and to determine when emergence occurs for different species. These traps are useful to determine local and regional occurrences and provide a guide for orchard managers to help them anticipate when various coneworms may appear.

DeBarr et al. (1982) described a southwide trapping effort for the webbing coneworm, I), disclusa Heinrich which indicated population densities and trends throughout the south. Also, substantial differences in moth emergence times in different parts of its range were evident.

Pheromones or attractants are available for four southern Dioryctria spp. including D. disclusa, the southern pine coneworm D. amatella (Hulst), the blister coneworm .ID. clarioralis (Walker), and the loblolly pine coneworm D. merkeli Matuura & Monroe. Since substantial cross-attraction occurs, all four of the aforementioned coneworms may be monitored with only two sets of pheromone baits and traps (Hanula et al. 1984). One set of baits monitors for D. amatella and the other set can monitor the other three species. In the future, it may be possible to use pheromones to more precisely predict optimum spray timing. Preliminary spray timing models have been developed and will be tested in 1985 and 1986 (J.L. Hanula, G.L. DeBarr and C.W. Berisford, unpub­ lished) . Future research should increase the utility of pheromones in seed orchards, but progress is most likely to be by degrees rather than by leaps and bounds.

93 Hardwood Borers

An attractant has been identified and synthesized for the carpenterworm moth, Prionoxystus robinae (Peck) (Doolittle et al. 1976). These attractants, though not yet included in any type of control program, can be used for surveys and may be useful help in timing control efforts (Dix et al. 1984).

Gypsy Moth

Surveys for the gypsy moth, Lymantria dispar L. have successfully utilized pheromone traps for a number of years. As the moth expands its range into the South, traps have increasingly been deployed in grids or in "high risk" areas to accurately delineate known infestations and/or to increase the chance of early detection of infestations. Pheromone traps are the most reliable and economical means of early detection since larvae and/or egg masses are extreme­ ly difficult to detect at very low densities (Schwalbe 1981).

Pheromone-baited traps may be utilized as direct control in isolated, sparse populations. Schwalbe (personal communication) has shown that pheromone traps deployed at high densities are effective controls, apparently by trapping out males before they can locate and mate with the relatively scarce females.

Summary

The optimistic predictions often made for forest insect pheromones as direct control agents during the 60's and 70's have generally not been borne out. However, the examples discussed here show that pheromones can be realis­ tically and effectively integrated into forest pest management systems. These techniques should become more useful in the future as refinements are incor­ porated into the various detection and/or control systems. Also, additional techniques utilizing pheromones for other insects will become available as more research data are accumulated.

References Cited

Berisford, C.W. 1982. Pheromones of Rhyacionia spp. Identification, function and utility. pp. 23-30. _In M.S. Blum (ed.), Communication in insects symposium. J. Ga. Entomol. Soc. 17 (2nd Suppl.) 38 p.

Berisford, C.W. and R.L. Hedden. 1978. Suppression of male Rhyacionia frustrana response to live females by the sex pheromone of R. buoliana and R. subtropica. Environ. Entomol. 7:532-533.

Berisford, C.W., P.M. Gargiullo and C.G. Canalos. 1984. Optimum timing of insecticidal control of the Nantucket pine tip moth. J. Econ. Entomol. 77:174-177.

Copony, J.A. and C.L. Morris. 1972. Southern pine beetle suppression with frontalure and cacodylic acid treatments. J. Econ. Entomol. 65:754-757.

94 Coulson, R.N., J.L. Foltz, A.M. Mayyasi, and F.P. Hain. 1975. Quantitative evaluation of frontalure and cacodylic acid treatment effects on within- tree populations of the southern pine beetle. J. Econ. Entomol. 68:671-678.

DeBarr, G.L., L.R. Barber, C.W. Berisford, J.C. Weatherby. 1982. Pheromone traps detect webbing coneworms in loblolly pine seed orchards. South. J. Appl. For. 6:122-127.

DeBarr, G.L., C.W. Berisford, J.L. Hanula. 1984. Use of sex pheromones for seed and cone insect pest management in conifer seed orchards, pp. 194-204. In H.O. Yates III (ed.), Proc. IUFRO cone and seed insects working party 52.07-01. Southeast. For. Exp. Sta. Pub. 214 p.

Dix, M.E., J.D. Solomoon, and R.E. Doolittle. 1984. Effectiveness of hollow fiber dispensers of synthetic sex attractant for male carpenterworms (Lepidoptera: Cossidae). Environ. Entomol. 13:737-740.

Doolittle, R.E., W.L. Roelofs, J.D. Solomon, R.T. Carde and Morton Beroza. 1976. (Z,E)-3,5-Tetradecadien-l-ol acetate sex attractant for the carpen­ terworm moth, Prionoxystus robiniae (Peck) (Lepidoptera: Cossidae). J. Chem. Ecol. 2:399-410.

Gargiullo, P.M., C.W. Berisford, C.G. Canalos, and J.A. Richmond. 1983. How to time dimethoate sprays against the Nantucket pine tip moth. Ga. For. Comm., Ga. For. Res. Pap. 44, 11 pp.

Gargiullo, P.M., C.W. Berisford, C.G. Canalos, J.A. Richmond and S.C. Cade. 1984. Mathematical descriptions of Rhyacionia frustrana (Lepidoptera: Tortricidae) cumulative catches in pheromone traps, cumulative eggs hatching, and their use in timing of chemical control. Environ. Entomol. 13:1681-1685.

Gargiullo, P.M., C.W. Berisford, and J.F. Godbee, Jr. 1985. Timing chemical control for the Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Torticidae) in the southeastern coastal plain. J. Econ. Entomol. 78:148-154.

Hanula, J.L., C.W. Berisford, and G.L. DeBarr. 1984. Pheromone cross­ attraction and inhibition among four coneworms, Dioryctria spp. (Lepidoptera: Pyralidae) in a loblolly pine seed orchard. Environ. Entomol. 13:1298-1301.

Ollieu, M.M. 1969. Evaluation of alternative southern pine beetle control techniques. Tex. For. Serv. Publ. 104. 6 pp.

Payne, T.L., J.E. Coster, and P.C. Johnson. 1977. Effects of slow release formulations of synthetic Endo- and Exo- Brevicomin on southern pine beetle flight and landing behavior. J. Chem. Ecol. 2:133-141.

Payne, T.L., L.H. Kudon, K.D. Walsh, and C.W. Berisford. 1985. Influence of infestation density on suppression of Dendroctonus frontalis infestations with attractant. Z. Angew. Entomol. In press.

95 Richerson, J.V., and T.L. Payne. 1979. Effects of bark beetle inhibitors on landing and attack behavior of the southern pine beetle and beetle associ­ ates. Environ. Entomol. 8:360-364.

Richerson, J.V., F.A. McCarty, and T.L. Payne. 1980. Disruption of southern pine beetle infestations with frontalure. Environ. Entomol. 9:190-193.

Schwalbe, C.P. 1981. The use of attractants in traps - Disparlure-baited traps for survey and detection, pp. 542-549. In Doane, C.C. and M.L. McManus (Eds.), The gypsy moth: Research toward integrated pest manage­ ment. U.S. Forest Serv. Sci. and Ed. Admin. Animal and Plant Health Insp. Serv. Tech. Bull. 1584. 757 pp.

Vite, J.P. 1970. Pest management systems using synthetic pheromones. Contrib. Boyce Thompson Inst. 24:343-350.

96 BIOLOGICAL AND NATURAL CONTROL OF

FOREST INSECTS — AN UPDATE

Harry C. Coppel Department of Entomology University of Wisconsin Madison, WI 53706

During the past twenty years, since your last symposium on "Insects in Southern Forests", many attempts have been made to evaluate progress in the protection of our food and fibre from the ravages of insect and weed pests. Supportive of these evaluation attempts are three recent occurrences in North America. Biological Control in the Canadian Forestry Service (Hulme 1982) presented a review of research and the development of future plans for research in biological control in Canada. The first National Interdisciplinary Biologi­ cal Control Conference (Battenfield 1983), utilizing the Nominal Group Tech­ nique, attempted to establish research direction and priorities in biological control in the U.S.A. by bringing together entomologists, plant pathologists and weed scientists. The Research Planning Conference on Biological Control (U.S.D.A. 1984) attempted, as did the Canadian Forestry Service, to establish needs and provide guidance to the Agricultural Research Service in their biological control decisions. Interestingly, all three addressed the question of increasing the diversity, abundance, and effectiveness of beneficial agents either through their introduction or manipulation, or through habitat manage­ ment. We, here, are particularly interested in the recent biological control strategies that have been suggested, developed, and utilized against forest insect pests.

To prevent semantic differences, my definition of biological control, in its narrow classical sense, is generally restricted to the introduction, by man, of parasitoids, predators and/or pathogenic microorganisms to suppress populations of plant or animal pests. Natural control, on the other hand, infers no human intervention whatsoever, and includes the non-pest species as well as the potential-pest species which are in dynamic equilibrium with their environment. Biological pest suppression, which is terminology I prefer, incorporates both the widely accepted classical biological control as well as the recently developed strategies which utilize the products of biotic agents (hormones, pheromones, semiochemicals, etc.).

The conservation and maintenance of both our present and future forests is crucial to assure an adequate wood supply. An essential element of sound forest management therefore is the protection of this resource from forest insect pests. It is my opinion that the forest ecosystem is a natural for either classical biological control or biological pest suppression. Forestry as a practice differs from agricultural pursuits because it takes longer for the crop to reach maturity and in addition the financial returns per hectare on an annual basis are much lower. Because of the latter, any measures taken to protect the forest crop must be low in cost and lasting in effect. At the same time, consideration must be given to the effects the protective measures have on the complex ecosystem involved. Most forest entomologists are cognizant of the dynamics of the insect populations which they seek to suppress, and, early on, because of costs, they were more hesitant to use the direct methods

97 commonly used by agricultural entomologists. This has changed considerably over the past 25-35 years with the rapid development of aerial methods of application.

The level at which forest insect pests must be suppressed is generally much higher than that demanded by agricultural pests. Most deciduous trees, for instance, can survive total defoliation for two or more years. This is because they are usually able to send out a second flush of leaves late in the season when the insect pest no longer is feeding. As a consequence, the loss of both height and diameter growth may be so small that protective costs need not be considered. Coniferous trees, on the other hand, very often can be killed by a single years total defoliation particularily if tender bark has been fed upon and also if there is feeding damage to the terminal buds which provide the next years growth. Many coniferous defoliators do not strip the tree in a single season but rather take several years of high populations to kill it. Trees stressed or weakened by heavy defoliation may succumb to secondary invaders but in many instances in natural stands some tree mortality can be tolerated.

Pest suppression may be accomplished by prevention or cure, hygiene or therapy (Balch 1957). Prevention is certainly more desirable than cure, and, of course, the goal that would be ideal would be the establishment of a resis­ tant forest. In such a forest, all the factors that regulate insect numbers must be combined in such a way that the crop can be grown, harvested, and reproduced without disturbing them. The completely resistant forest will remain an ideal until much more is known ecologically about the various trees and pest species, the cause of outbreaks, etc., etc. so that the information can be utilized into practical silvicultural management. Therapy and hygiene in their proper ratios will have to do for the time being in suppression of forest insect pests.

Silvicultural pest suppression incorporates the techniques for growing and harvesting the forest crop so that there is a minimum of insect damage. It includes almost all the known methods of prevention other than those included in classical biological control and as a consequence is synonymous with forest hygiene. Silvicultural practices that favor tree growth will seldom conflict with, and will often coincide with protection from insects and their damage.

Classical biological control is a form of therapy even though its end result may be considered hygienic. Against forest insect pests it have been practiced most extensively in Canada and the United States (Hulme and Green 1984, Turnock, et al. 1976, Waters et al. 1976). The reason for this is straightforward. Many of our major insect pests arrived with the immigrants who often brought along infested plant materials from the Old World, or through commerce (e.g. dumping of ballast, etc.). It was only natural therefore to introduce beneficial organisms against these pests from their country of origin. It has not always been a one-way street from the Old to the New World. The fall webworm is an excellent example of a New World species which has become a pest in the Old World. This category of biological control is re­ ferred to as innoculative release and was the first widely applied strategy which involved entomophagous arthropods. Two additional major categories, inundative release and environmental manipulation are generally accepted by biological control workers (Nordlund 1984). I plan to discuss these in reverse order.

98 Environmental Manipulation

There has been an almost total neglect of environmental manipulation in current forest pest suppression strategies utilizing biological control agents in North America. Most aspect of manipulation have involved the agroecosystem rather than the forest ecosystem. However, prefabricated nest boxes and other forms of shelter have been used successfully for many years in the forested areas of Europe (particularly Germany) to attract and hold insect-eating birds. We do not seem to have the same need in North America for providing shelter, nesting and roosting sites for birds. Little current activity has been report­ ed. A reliable food supply must be available in the environment at the proper time of year to maintain and increase entomophagous arthropods. This is often possible through the use of artificial supplements or through plant diversity which supplies either alternate acceptable hosts or prey or nourishment for certain adult parasitoids and immature and mature insect or mite predators. In Columbia, South America, it is considered and economic option to spray a 20% honey solution on grasses and low shrubs to attract and hold adult parasitoids of forest defoliators (Madrigal-Cardeno, personal communication). Similarly small bottle caps containing sugarcane molasses were placed on the soil to attract hymenopterous adults particularly when natural vegetation was limited.

Adults of many parasitic Diptera and Hymenoptera visit flowering plants (e.g. Umbelleferae) for honey or nectar, often a requirement for egg formation. Establishment and success in Canada of the exotic Orgilus obscurator against the European pine shoot moth was dependent on the presence of wild carrot for maximum effectiveness. Though originally declared a noxious weed, it is now possible for plantation owners to utilize this weed species and trials are currently underway in the Maritime Provinces of Canada (Nova Scotia).

Survival of monophagous (specific) beneficials between outbreaks of major insect-pests of forest crops often presents major problems. The gypsy moth, in Europe, has periods between outbreaks when their numbers are very low. To circumvent the dispersal of the beneficials to other areas, gypsy moth egg masses have been added to the environment both to increase the density of the host organisms and to retain and build populations of the common egg parasi­ toids. This is a chancy procedure, in my opinion, unless nonviable egg masses are used.

Inundative Release

Inundative releases have been used infrequently against forest insect pests. The releases are analagous to insecticidal treatments in that a greater amount of liberated material (biotic agents) is used than is actually effective and there is-no dependence on their progeny. Repetition of the release may be nececssary but the effect is more or less immediate. Recent inundative releases of Trichogramma minutum (T.m.) against the spruce budworm were undertaken by Carrow et al. (1984) in Canada. Both ground (1983) and aerial releases were made (1983 and 1984). Ground releases of 12 million T.m. females/ha resulted in a parasitization rate of 41% on white spruce and 64% on balsam fir. Aerial releases (2) in 1984, utilizing 15 million T.m. females/ha, released seven days apart, showed over 80% parasitization of the naturally occurring budworm egg masses and over 75% of the eggs in each mass were attacked. It was felt that inundative releases of T.m. utilizing helicopters could achieve routine levels of parasitization in excess of 50%. China has

99 been using Trichogramma dendrolimi in inundative releases against defoliators in the genus Dendrolimus for many years but little precise quantitative information is available from their studies. It is known that their communes utilize silkworm eggs in which 40-60 Trichogramma can mature from each egg. In North America, mass production techniques utilize eggs of Sitotroga from which only one parasitoid emerges per egg. In Russia, Trichogramma evanescens has been released against the European pine shoot moth with considerable success.

Inoculative Release

This strategy relies on the introduction, release, and establishment of beneficial organisms and their natural spread through the pest population. Included among the beneficial organisms are the parasitoids, predators and microbial pathogens (entomopathogens). It is not my intention to provide you with an historic list of either all the beneficials or all the forest insect pests against which they have been released. These you can find in the review articles already cited. Because this is an update, I plan, hopefully, to provide you with the current situation on some of the more serious forest insect problems. As most of you are aware considerable federal funding has, of late, gone into in-depth studies on development of management plans for the southern pine beetle, the gypsy moth, the Douglas-fir tussock moth and most recently the eastern and western budworms. I will address these species first and then comment on additional biological control projects which have main­ tained some activity in the recent past.

The management of the southern pine beetle has already been discussed and there is little to add. This project has provided us with a wealth of informa­ tion some of which may lead to the utilization of biological control agents. Though there appears to be no active biological control program in the U.S.A. the Canadians (Hulme 1982) have stated that bark beetles are the most serious insect pests of mature western conifers. Hulme and Green (1984) recommended that perhaps the whole range of biological control agents be given closer examination, particularly for the native western Dendroctonus species. When this recommendation will be activated remains to be seen.

The gypsy moth is not native to North America but has been here since before the turn of the century. It appears to be spreading in all directions from its original infestation area in the northeast. Inoculation releases of parasitoids and predators were initiated early in the century and continue to this day. Over 40 beneficials have been introduced and released and some 12 have some 12 have become established. The search for additional beneficial species from the Orient are continuing wherever Lymantria or closely related species occur. For the most part it has been difficult to evaluate the effec­ tiveness of the releases because of control efforts utilizing chemical insecti­ cides. There are reports, however, or both significant reductions of high gypsy moth populations or the maintenance of stable, tolerable populations in certain areas.

Microbial pathogens, particularly the bacterium Bacillus thuringiensls (B.t.) has been in commercial production for several decades and is approved for use against lepidopterous pests including the gypsy moth. The kurstaki strain is apparently the most virulent strain to date, however, the search for more virulent strains is a never ending one. Foliage protection is assured with the use of this bacterium and it can be applied as one would apply a

100 chemical insecticide. There is neither environmental contamination nor mortal­ ity to adult parasitoids or predators in the spray area. Another pathogen, a nucleopolyhedrosis virus (NPV) has also been approved for use against the gypsy moth. Mortality from this pathogen has been erratic, however research is continuing on both the development of strains with high virulence and on application technology.

The Douglas-fir tussock moth, a native insect pest, has periodically defoliated large forested areas in both western United States and Canada. Though B.t^. was utilized early on it did not prove satisfactory. At the same time studies were underway on the NPV and registration was obtained in 1975 in the U.S.A. Population reduction in Canada following aerial application varied between 82 and 90% approximately. Shepherd et al. (1984) using both ground and aerial applications of the virus recorded up to 85% and 100% infection respec­ tively, of tussock moth larvae. They were successful in the prevention of an outbreak through early treatment. No further virus treatments have been recorded in the United States since shortly after registration.

The complex of native budworms (Choristoneura spp.) in both United States and Canada has been responsible for tremendous losses to susceptible forests. The eastern spruce budwoorm in Canada is considered the dominant forest pest problem at the present time. Short term approaches utilizing chemical insecti­ cides, bacteria, viruses etc. have not worked to date except for a certain degree of foliage protection. The only long term approach to controlling these forest pests appears to be through manipulations of parasitoids or predators. We have already discussed inundation releases of Trichogramma as a promising approach. The search for exotic parasitoids and predators from closely related hosts or prey have been recommended but not yet implemented to my knowledge.

Most of the remainder of the recent biological control examples I will provide vary considerably in their approach and in the beneficials employed. The transfer of established exotic parasitoids within a country is a common occurrence. Two established exotic parasitoids of the European winter moth were transferred from Nova Scotia to British Columbia and Oregon between 1979 and 1981. Both species were recovered in 1982 in British Columbia and their numbers had increased considerable by 1984. Success of this program is expect­ ed (I.S. Otvos personal communication). Similarly Drooz (personal communica­ tion) recorded two successful transfer programs. He transferred two cocoon parasitoids of the introduced pine sawfly from Wisconsin to North Carolina from 1979 to 1981. Monodontomerus dentipes responsed to the populations surge of the introduced pine sawfly and, in 1980, parasitized almost 45% of the cocoons. Parasitization dropped in 1981 and 1982 when the pine sawfly infestation collapsed. The other parasitoid transfer was against the larch sawfly in Pennsylvania. He transferred Olesicampe benefactor from Minnesota in 1975 and by 1983 it was found in 59% of the dissected host cocoons at the release site. Additional transfers from this release site were made in 1980 and 1982 to guard against its possible extinction. In Wisconsin, we arranged a transfer of the exotic Lophyroplectus oblongopunctata from Ontario in 1977. This was against the European pine sawfly and by 1980 we were able to collect and move parasi­ toid adults around within the state. We contaminated the adults with the NPV of the sawfly to aid in its dissemination.

A massive, well organized, biological control program against the larch casebearer was undertaken in the Pacific Northwest. Not only were established

101 exotics moved from Eastern to Western United States but additional exotics were introduced from around the world. The two previously established eastern exotics (Agathis and Chrysocharis) are now widely established at almost all the release locations in Oregon and are providing tremendous casebearer reductions (R.B. Ryan personal communication). Complete life tables of this study have been maintained since 1979 on three plots and should eventually provide one of the most complete analysis of a biological control project undertaken by the Forest Service.

One of the most impressive and successful control programs of the mid- 1970s was the transfer of an egg parasitoid from Virginia, USA, to Columbia, South America (Bustillo and Drooz 1977). The parasitoid Telenomus alsophilae, reared from the fall cankerworm, was successfully established in Oxydia trychiata in Columbia. It is the only example in forest entomology of the intentional use of a parasitoid of one insect genus to control an insect in a different genus. The parasitoid also had to survive under ecological and climatic conditions considerably different from those in which it originated. Success was rapid, within six weeks of release 56-90% of the egg masses and 95-99% of the eggs in each mass were parasitized. The outbreak was controlled within six months. The strategy of utilizing parasitoids from allied genera against native pests has received considerable support. Hokkanen and Pimentel (1984) compared the success rate utilizing old associations as in most early classical biological programs and new associations similar to the above. With the old associations it required about seven natural enemies per success whereas with new associations it required only about four per success. The lack of evolved interspecific balance in new associations appears to explain the higher success rate. Fifty randomly selected pest species were used for their evaluations.

My final example involves the use of a nematode in the suppression of Sirex woodwasps in Tasmania, Australia, and New Zealand. Sirex noctilio, an introduced pest, was responsible for the death of at least 40% of the exotic Monterey pine treees in plantations. The nematode Deladenus siricidicola was reared from Sirex and its complex mycetophagous - entomophagous relationships clarified. The nematodes could be mass produced in the laboratory along with their necessary food fungus in the genus Amylostereum. The nematode-fungus combination was then inoculated into felled timber and eventually infected the Sirex woodwasps. Bedding (1979) developed a sophisticated system for propagat­ ing and distributing this combination. Field-trials were initiated in 1970 and by 1974 over 70% of all the tree contained nematodes and over 90% of the emerging Sirex were parasitized by the nematodes. The number of trees killed by Sirex dropped dramatically and by 1976 no tree mortality was recorded. There has been considerable natural spread of the nematode to nearby forests as far away as 13 kilometers. Evaluations are continuing.

Before closing, I wish it known that I am a staunch supporter of the Integrated Pest Management (IPM) concept as a holistic approach to pest sup­ pression and whose purpose is, in part, to reduce pesticide use. In most countries pesticide use is still increasing and at the same time pest problems and losses are not decreasing. Biological control, an area in which I have spent my entire career, is supposedly in the center of, or is a cornerstone of any IMP program. My concern is that this may be true in developing countries to a much greater extent than in the developed countries. Developing countries are labor intensive, have strong political support for this approach, have

102 effective contacts between all levels concerned, communal and cooperative organization makes it possible to carry out the above, and there is the absence of a commercial interest in pest-control products or information (Corbet 1981, Shin-Foon 1984). Developed countries, on the other hand, have constraints that are non-entomological and often act as impediments to IPM programs. It seems to me, that in developed countries, the biological control gate is barely open and I am concerned that the IPM concept is totally engulf­ ing the discipline of biological control, providing rhetoric but little sup­ port. We, in biological control must open the gate wide to ensure that our beneficials are being protected from chemical pesticides. It is encouraging to report that several small companies have recently begun to produce nematodes for use against forest products pests and registered viruses against sawflies.

Literature Cited

Balch, R.E. 1958. Control of forest insects. Annu. Rev. Entomol. 3:449-468.

Battenfield, S.L. (ed.). 1983. Proceedings of the national interdisciplinary biological control conference. U.S.D.A., C.S.R.S., Wash., D.C., 107 p.

Bedding, R.A. 1979. Manipulating the entomphagous-mycetophagous nematode, Deladenus siricidicola for biological control of the woodwasp Sirex noctilio in Austrialia. In: Current Topics in Forest Entomology. U.S.D.A., For. Serv. Gen. Tech. Rept. W0-8. p. 144-147.

Bustillo, A.E., and A.T. Drooz. 1977. Cooperative establishment of a Virginia (USA) strain of Telenomus alsophilae on Oxydia trychiata in Columbia. J. Econ. Entomol. 70:767-770.

Carrow, J.R., S.A. Nicholson, and B.H. McGauley. 1984. Trichogramma and the spruce budworm - an update. CANUSA Newsletter 37. (Nov.).

Corbet, P.S. 1981. Non-entomological impediments to the adoption of integrat­ ed pest management. Prot. Eco.. 3:183-202.

Hokkanen, H., and D. Pimentel. 1984. New approaches for selecting biological control agents. Can. Entomol. 116:1109-1121.

Hulme, M.A., and G.W. Green. 1984. Biological control of forest insect pests in Canada 1969-1980: Retrospect and prospect. In: Kelleher, J.S., and M.A. Hulme (eds.). Biological control programs against insects and weeds in Canada 1969-1980. Commonwealth Agricultural Bureau, p. 215-227.

Nordlund, D.A. 1984. Biological control with entomophagous insects. Sec. Suppl., J. Georgia Entomol. Soc. 19:14-28.

Shepherd, R.F., I.S. Otvos, R.J. Chorney, and J.C. Cunningham. 1984. Pest management of Douglas-fir tussock moth (Lepidoptera: Lymantriidae): Prevention of an outbreak through early treatment with a nuclear polyhedrosis virus by ground and aerial applications. Can. Entomol. 116:1533-1542.

103 Shin-Foon, C. 1984. Recent advances in the integrated control of rice insects in China. Bull Entomol. Soc. Amer. 30:41-46.

Turnock, W.J., K.L. TAylor, D. Schroder and D.L. Dahlsten. 1976. Biological control of pests of coniferous forests. In: Theory and Practice of Biological Control. C.B. Juffaker and P.S. Messenger (eds.). Academic Press, New York, San Francisco, London, p. 289-311.

U.S.D.A. 1984. Research planning conference on biological control. Agric. Res. Serv., Washington, D.C. 473 p.

Waters, W.E., A.T. Drooz, and H. Pschorn-Walcher. 1976. Biological control of pests of broad-leaved forests and woodlands. In: Theory and Practice of Biological Control. C.B. Huffaker and P.S. Messenger, (eds.). Academic Press, New York, San Francisco, London, p. 313-336.

104 DECREASING LOSSES DUE TO WOOD DETERIORATION THROUGH PROPER FORESTRY PRACTICES

Terry L. Amburgey Associate Professor, Wood Science and Technology Mississippi Forest Products Utilization Laboratory Mississippi State University

Junk-in, junk-out is the lament of many wood processing plant foremen. What they are saying is that the quality of products produced depends on the quality of wood received by the manufacturing facility. The most skilled utilization forester cannot saw high-grade lumber from stained or beetle- infested logs or produce quality furniture from decayed stock. Proper handling of raw materials is the name of the game, and this largely is the province of the field forester.

Basically, proper handling of raw materials falls into three separate phases of a company's operation: (1) coordination of field activities to assure the delivery of sound, insect- and fungus-free logs (bolts, poles, etc.) to the storage yard; (2) establishment of storage practices to assure the movement of defect-free logs (bolts, poles, etc.) to the processing plant; and (3) develop­ ment of procedures for handling primary products (lumber, chips, poles, etc.) during seasoning or storage prior to their fabrication into finished products. But before a field forester can intelligently develop a system for handling raw materials during these three phases, he must thoroughly understand the types of products produced by his company and the materials required in their manufac­ ture.

Field Activities

The best practice for most forestry operations is to reduce the time between felling and transport to an absolute minimum, especially during the summer in the South. Yarding and storing logs in the woods during weather above 50°F almost invariably results in colonization of logs by fungi and beetles. This may be of little consequence for some companies, but for others (e.g., log home producers), as will be discussed below, this may prove to be disastrous. Ideally, felling and utilization phases, should be coordinated to minimize the time that logs (bolts, poles, etc.) spend in the storage yard.

Storage Practices

First-in, first-out is the key to minimizing defects in logs (bolts, poles, etc.) during storage. Material should move systematically through the yard to the mill in a timely fashion. If storage must be extended past a few days, especially between March and November in the South, stored material must be protected from degrade by fungi and insects. Depending on the length of storage time, the type of material being stored, and the physical layout of the storage yard, protective measures may include ponding, water sprays, encapsula­ tion, biocide sprays, or end coatings (Amburgey 1979).

Ponding and Water Sprays.— If the increased permeability of stored material is inconsequential, ponding or water sprays can protect logs or bolts from

105 fungi and insects for over a year by filling exposed pores with water and thereby reducing the amount of oxygen they hold. Checking also is reduced in water-stored wood. It must be remembered, however, that with ponding only those portions of logs that are submerged will be protected; fungi and insects can colonize the non-soaked portions of ponded stock. Although water-soaked wood cannot be colonized by fungi and insects, bacteria can colonize material stored under water (DeGroot and Scheld 1973). Bacteria primarily utilize nutrients stored in parenchyma cells, so permeability and loss in toughness increase progressively with time of storage due to breakdown of cell walls of ray parenchyma (Scheld and DeGroot 1971).

Water storage should be used with caution with materials to be used in products where increased permeability could result in problems during manufac­ ture (e.g., veneer bolts or millwork stock). Veneer cut from bolts stored under water for extended periods of time will require more glue than fresh stock is used in products such as plywood. Similarly, water—stored millwork stock will over-absorb paints or other finishes. In most instances, however, the benefits of water storage far outweigh the disadvantages (Carpenter and Toole 1963, Brodie and DeGroot 1976). In general, changes in the permeability and toughness of stored material can be minimized by reducing water storage to le$s than three months. No loss of strength or yield of pulp has been experi­ enced in pulpwood bolts stored under water sprays (Volkman 1966). Unlike roundwood, however, water sprays will not protect chip piles from degrade; the strength of pulp from water-sprayed chips decreases with time of storage (Djerf and Volkman 1969).

Encapsulation.— Encapsulating freshly-cut roundwood in polyethylene is another way to protect it from fungi and insects by decreasing oxygen to levels than cannot support their growth. As the wood cells continue to respire, the relative ratio of carbon dioxide to oxygen increases. Although this storage procedure has not been used commercially, a 2000 cord pile of freshly-cut pulpwood bolts was protected for over two years by being covered with 20-mil block polyethylene (McKee and Daniel 1966). Encapsulation also would be useful in protecting chips from physical and biological deterioration (Feist et al. 1971).

Biocide Sprays and End Coatings.— Logs to be stored for three to four months can be protected from fungi, insects and checking by applying a fungicide/- insecticide mixture to all exposed surfaces and coating the end grain with a substance to control loss of moisture. These treatments, however, must be completed within one or two days, and preferably 24 hours, after felling (Sheffer and Lindgren 1940, McMillen 1956). Biocides may be applied by spray­ ing or dipping, but all surfaces must be treated. Solutions of pentachloro- phenol and benzene hexachloride (BHC) have been used to protect logs in the past (Wagner 1978), but BHC no longer is considered £ o be safe for this use by the Environmental Protection Agency (EPA). Lindane was substituted for BHC, but now the use of this biocide, as well as pentachlorophenol, is being ques­ tioned by the EPA (Kelly 1983, USDA). Ambrodan (endosulfan) now l^s a federal label for beetle control in logs. Fungicides such as Polyphase (3 iodo-2- propynyl butyl carbamate), Busan [2-(thiocyanomethyl) benzothiazole P ^ s methylene-bis-thiocyanate], or diffusible boron compounds (e.g., TimBor )

Note: Use of tradenames does not constitute endorsement of these products.

106 likely will be used to protect logs in the future. Several end coating prod­ ucts are commercially available.

Seasoning and Storage of Primary Products.—— Hardwood lumber and other prod­ ucts (e.g., cross ties), as well as poles and piles not steam—conditioned prior to treatment, require several weeks or months of seasoning to reduce their moisture content before further processing or treatment with preservative chemicals (McMillen and Wengert 1978). As with logs, hardwood lumber often has been treated with mixtures of sodium pentachlorophenate and lindane, but this practice likely will be discontinued. Fungicides such as Busan, Polyphase, zinc naphthenate, copper—8-quinolinolate, or diffusible boron compounds, with or without insecticides such as endosulfan or chlorpyrifos, likely will be used to treat these materials in the future. Several other chemicals also are being tested (Cserjesi and Johnson 1982, Eslyn and Cassens 1983, Cassens and Eslyn 1983, Becker 1956, Roff 1974, Williams and Amburgey 1985, Williams and Mauldin 1985). Regardless of which biocides are used to protect materials during seasoning and storage, it is essential to have proper air-drying facilities (Reitz and Page 1971).

Several companies are converting from pulpwood to chip storage and, like roundwood, chips are subject to biological and physical deterioration (Sheffer 1969; Koch 1972a,b). Both encapsulation, as discussed above, and treatment with biocides can prevent chip deterioration (Eslyn 1973a,b; Springer et al. 1977). As with roundwood, however, rapid utilization and application of the first-in, first-out rule is the best method of preventing deterioration of chip inventories.

The Log Home Industry

In the last few years, several companies in the South have begun producing log home kits. While some of these companies have experienced no significant problems with their products, others have had several complaints from dissat­ isfied homeowners (Amburgey and Williams 1982). After inspecting a large number of log homes, it became evident that owners of pine log homes in the South primarily are troubled by three problems: (1) buprestid beetles emerging from logs of homes 0-5 years old, (2) wood decay in homes 0-5 years old, and (3) old house borers emerging from logs of homes 2-5 years old (Amburgey and Williams 1984). In many instances, all three of these problems can be traced to poor log handling, storage or seasoning practices.

Buprestid Beetles.-"- The emergence of buprestid adults, primarily Buprestis lineata (Fab.), from logs indicates that the field foresters employed by these companies do not understand the restrictions placed on their activities by the type of product being produced and, perhaps, indicates that many companies in the South have developed sloppy log handling practices. B. lineata adults lay their eggs in the cracks and crevices of bark. If the bark is not removed within two to three weeks during the spring or summer, and the logs are stored without protection, buprestid adults may lay eggs, the eggs hatch, and some larvae tunnel from the bark into the outer sapwood. Subsequent debarking only causes the larvae to feed deeper in the sapwood as the logs begin to dry. With most operations, buprestid infestation of logs would be of little consequence since the outer sapwood is slabbed from the logs and the lumber kiln-dried. With logs to be used for structures, however, very little sapwood is removed

107 during the debarking and shaping operations. In addition, most logs used for structures are neither kiln-dried nor pressure treated with preservative chemicals. Most companies dip-treat their logs with preservative chemicals, but these biocides do not penetrate logs more than a few millimeters. These treatments will not kill beetle larvae feeding in the logs.

Decay Fungi.— Periodically, decay fungi are observed growing on logs while a home is still under construction. As with the buprestid beetles, this indi­ cates that the logs were stored for extended periods of time without protec­ tion. Dipping logs in biocides after they have been colonized by decay fungi will not stop the growth of these fungi. As long as the moisture content of the logs remains above 30%, decay fungi will continue to grow and cause decay.

Old House Borers.— Old house borer (Hylotrupes bajulus L.) adults, contrary to their common name, lay their eggs in cracks and crevices of debarked wood that has been recently processed, partially seasoned, or in service for up to about ten years. While many old house borer infestations occur after a home is erected, evidence suggests that at least some infestations occur while logs are stored at the manufacturing plant. If debarked logs or kits must be stored during May through August in regions where old house borers are common (Florida and Atlantic coast states northward to Massachusetts), they should be treated with biocides following shaping and should be protected from rainwetting.

Summary

In summary, field foresters must understand the types of produces produced by their company, and the raw materials required for their manufacture, before they can intelligently develop procedures for supplying the processing plant with quality material. Minimizing inventories and assuring the systematic movement of materials from the storage yard to the manufacturing facility will assure that degrade of raw materials will be minimized.

References

Amburgey, T.L. 1979. Minimizing degrade in wood inventories. South. Lumber­ man 238(2945):13-15.

Amburgey, T.L. and L.H. Williams. 1982. Constructing log homes in the South. Miss. For. Prod. Util Lab., Information Series No. 22. 6 p.

Amburgey, T.L. and L.H. Williams. 1984. Constructing log homes in the South. II. Common problems and their prevention. Log Home Guide for Builders and Buyers 7(3):30,32,33,74,75.

Becker, G. 1976. Treatment of wood by diffusion of salts. J. Inst. Wood Sci. 7(4), (40):30-36.

Brodie, J.E. and R.C. DeGroot. 1976. Water spray storage: a way to salvage beetle-endangered trees and reduce logging costs. South. Lumberman 232(2877):13-15.

108 Carpenter, B.E., Jr., and E.R. Toole. 1963. Sprinkling with water protects hardwood logs in storage. South. Lumberman 207(2576):25-26.

Cassens, D.L. and W.E. Eslyn. 1983. Field trials of chemicals to control sapstain and mold on yellow-poplar and southern yellow pine lumber. For. Prod. J. 33(10):52-65.

Cserjesi, A.J. and E.L. Johnson. 1982. Mold and sapstain control: laboratory and field tests of 44 fungicidal formulations. For. Prod. J. 32(10):59-68.

DeGroot, R.C. and H.W. Scheld. 1973. Permeability of sapwood in longleaf pine logs stored under continuous water spray. For. Prod. J. 23(4):43-46.

Djerf, A.C. and D.A. Volkman. 1969. Experiences with water spray wood stor­ age. Tappi 52(10):1861-1864.

Eslyn, W.E. 1973a. Propionic acid—a potential control for deterioration of wood chips stored in outside piles. Tappi 56(4):152-153.

Eslyn, W.E. 1973b. Evaluating chemicals for controlling biodeterioration of stored wood chips. For. Prod. J. 23(11):21—25.

Eslyn, W.E. and D.L. Cassens. 1983. Laboratory evaluation of selected fungicides for control of sapstain and mold on southern pine lumber. For. Prod. J. 33(4):65-68.

Feist, W.C., E.L. Springer, and G.J. Hajny. 1971. Encasing wood chip piles in plastic membranes to control chip deterioration. Tappi 54(7):1140-1142.

Kelly, G.E. 1983. Integrated protection against structural wood-infesting pests. III. Southern hardwood production. The factors that determine its future. Pest Management Magazine, Vol. 2, Natl. Pest Control Assn.

Koch, P. 1972a. Utilization of the Southern Pines, Vol. I—The Raw Material. U.S. Dep. Agric., For. Serv. Agric. Handb. 420. p. 1-734.

Koch, P. 1972b. Utilization of the Southern Pines, Vol. II—Processing. U.S. Dep. Agric., For. Serv. Agric. Handb. 420. p. 735-1663.

McKee, J.C. and J.W. Daniel. 1966. Longterm storage of pulpwood in sealed enclosures. Tappi 49(5):47A-50A.

McMillen, J.M. 1956. Coatings for the prevention of end checks in logs and lumber. U.S. Dep. Agric., For. Serv., Rep. 1435. 13 p.

McMillen, J.M. and E.M. Wengert. 1978. Drying eastern hardwood lumber. USDA Forest Service, Agr. Handbook 528. 104 p.

Rietz, R.C. and R.H. Page. 1971. Air drying of lumber: A guide to industry practice. USDA, Forest Service, Agr. Handbook 402. 110 p.

109 Roff, J.W. 1974. Boron-diffusion treatment of packaged utility-grade lumber arrests decay in storage. Can. For. Serv., West. For. Prod. Lab., Info. Rep. VP-X-125.

Scheld, H.W. and R.C. DeGroot. 1971. Toughness of sapwood in water-sprayed longleaf pine logs. For. Prod. J. 21(4):33-34.

Sheffer, T.C. 1969. Protecting stored logs and pulpwood in North America. Mater. Org. 4(3):167-199.

Sheffer, T.C. and R.M. Lindgren. 1940. Stains of sapwood and sapwood products and their control. U.S. Dep. Agric., Tech. Bull. 714. 124. p

Springer, E.L., W.C. Feist, L.L. Zoch, Jr., and G. J. Hajny. 1977. Evaluation of chemical treatments to prevent deterioration of wood chips during storage. Tappi 60(2):92-97.

USDA. ND. The biologic and economic assessment of pentachlorophenol, inorgan­ ic arsenlcals, and creosote. Vol. 1: Wood preservatives. USDA Tech. Bull. 1658-1. 435 p.

Volkman, D. 1966. Water spray storage of southern pine pulpwood. Tappi 49(7):48A-53A.

Wagner, F.G., Jr. 1978. Preventing degrade in stored southern logs. U.S. Dep. Agric., For. Prod. Util. Bull. 4 p.

Williams, L.H. and T.L. Amburgey. 1985. Integrated protection against lyctid beetle infestations. IV. Resistance of boron-treated wood (Virola spp.) to insect and fungal attack. For. Prod. J. (in preparation).

Williams, L.H. and J.K. Mauldin. 1985. Integrated protection against lyctid beetle infestations. III. Implementing boron treatment of Virola lumber in Brazil. For. Prod. J. (in preparation).

1 1 0 IMPLEMENTING FOREST PEST MANAGEMENT - THE FORESTER'S ROLE

Ronald F. Billings Principal Entomologist Texas Forest Service Lufkin, Texas 75901

Prior to the 1970's, the forester's approach to insect pests in the South was relatively simple and straight forward. Major insect pests were few, consisting primarily of the southern pine beetle, pine sawflies, and reproduc­ tion weevils (Warren 1965, Williamson 1965). Pest problems, in most cases, were addressed simply by applying chemical controls when and where the need arose. In those days, insecticides such as DDT and BHC were readily available, inexpensive and served to control a wide variety of pests. Although the biologies of most pests were understood, little was known about the host/- environmental interactions that led to pest outbreaks. Clearly, under the circumstances, the "brute-force" approach was deemed the quickest and most efficient means to alleviate pest problems and avoid excessive resource losses (Williamson 1965).

Concepts of silviculture control, particularly for bark beetles, were known at that time. But there was not enough background in silviculture from which to draw conclusions about the resistance of timber stands to insect attack or to formulate a sound basis for indirect control (Bennett 1965). Besides, with low stumpage prices (ca. $30/MBF in 1964), surplus of pine timber, and the ready availability of effective and inexpensive insecticides, there was little incentive to consider silvicultural or other non-chemical controls for forest pests.

Needless to say, things have changed since the last LSU symposium on forest insects was held in 1965. During the last twenty years, the forester's job of meeting diverse management objectives while avoiding excessive resource losses from forest pests has become increasingly complex. To better cope with major pest problems such as the southern pine beetle, considerable efforts in recent years have been devoted to the development and application of integrated forest pest management (IFPM). Successful implementation of available IFPM technology, however, will necessarily require a committment from field foresters and a close working relationship with specialists in forest ento­ mology and pathology, computer science, silviculture, and pest management.

Important reasons why we need to consider a more ecologically sound and planned approach to forest pests are summarized below:

1. The inexpensive, broad spectrum insecticides we once relied upon to alleviate pest problems are no longer available. Most have been replaced by less persistent pesticides targeted at specific pests and/or crops. Many are legally restricted with respect to how they can be applied and by whom. The increased cost of toxic chemicals limits their use to certain high value situations (such as seed orchards, nurseries and Christmas tree plantations). Increased public concern for the quality of the environment has placed further constraints on opportunities for chemical control.

Ill ". In recent years, intensification of forestry practices and increased monetary investments have expanded the array of insects and diseases considered to be pests. For example, new complexes of pests have been generated by our establishment of pine seed orchards, increased acreage in exotic tree species, nurseries, Christmas trees, hardwood plantations and windbreak plantings. The minimum level of damage forest managers can allow before taking action (economic threshold) decreases in direct relation to the value of the investment.

3. Increasing acreages of commercial forest lands, particularly corporate lands, are being converted from natural sawtimber stands to young, even- aged pine plantations. In the last 10 years, over 1.2 million acres of Industrial lands have been regenerated to loblolly and non—native slash pine plantations in East Texas alone. Plantation pests—particularly fusiform rust and bark beetles—are likely to become more troublesome as these plantations mature, particularly if planned thinning schedules are not maintained (Billings 1984).

4. For the first time, sizable acreages in the South are being set aside for preserve and wilderness areas. In the last ten years in Texas alone, 84,000 acres of commercial forest have been set aside for the Big Thicket National Preserve and 34,000 acres have been removed from production for wilderness areas. Recent experiences with the Four Notch Proposed Wilder­ ness area in Texas (Texas Forest Service 1984) and the Kasatchie Hills Wilderness in Louisiana attest to the susceptibility of these areas to southern pine beetle outbreaks. These preserve areas present specialty problems for pest management, since prevention programs can not be prac­ ticed and direct control tactics have come under increasing criticism.

5. The threat of introduced pests is increasing, particularly that of the gypsy moth. In many states once considered outside the range of gypsy moth, eradication programs have been required to prevent establishment of this introduced, noxious defoliator. Such states include Virginia, North Carolina, South Carolina, Tennessee and Arkansas, as well as many mid- western and western states. Although Louisiana and Texas have escaped the establishment of gypsy moth infestations to date as far as I know, its probably only a matter of time before we are faced with this problem. Indeed, pheromone traps in Texas caught four male gypsy moths for the first time in 1984 in three different locations. We may already have a gypsy moth infestation we don't know about!

6. The South is rapidly emerging as the timber growing and processing center of the nation. The U.S. Forest Service predicts that demand for wood and wood products will double by the year 2020, if not sooner. Indeed, in East Texas, pine harvest has already begun to exceed pine growth (Skove 1984). We no longer enjoy a surplus of timber; if we hope to meet tomor­ row's wood demands, we must take preventive action now to protect our growing stock from excessive losses to insects and diseases. On the positive side, the increasing trend in the value of timber should make it economically feasible to incorporate more hazard rating systems (Hedden et al. 1981) and silvicultural manipulations into forest management to avoid certain pest outbreaks.

1 1 2 Coping with pests under these trying times will require an increased understanding of host/environmental/pest interactions and a cooperative, planned approach to pest management. Although for most forest pests we still lack the information and tools to establish comprehensive IFPM systems similar to those in agriculture, many of the concepts of pest management can and should be practiced by foresters and forest land managers.

What is integrated forest pest management and how does it differ from simple pest control? By definition, IFPM is a planned approach that coordi­ nates the intelligent use of all available information and suitable prevention and suppression methods in order to maintain pests at levels below those causing economic damage. A 1984 symposium summarized the current state-of-the- art concerning integrated management approaches to insects, diseases, vegeta­ tion and animal pests in southern forests, nurseries and seed orchards (Branham and Hertel 1984). I recommend that foresters add this valuable reference to their professional library.

A simple forest pest management scheme, adapted from that proposed by Cameron (1981) for southern pine seed orchards, is shown in Figure 1. In the IFPM approach, major pest problems are anticipated at each stage of forest establishment and development. To predict or to respond to a pest problem, information is gathered from all available sources and funneled into a decision support sub-system. This subroutine accumulates and processes current informa­ tion on the pest species and all other pertinent information required to assist the manager in making sound pest management decision.

The level of sophistication of any pest management system will vary with the pest(s) and host(s) involved as well as the information and resources available to address the problem. Accordingly, in the most elementary system, the forester or land manager makes pest control decisions based solely on his experience and any information on hand at the time. In an intermediate ap­ proach, the forester receives pest control recommendations from one or more trained specialists who usually have access to a more detailed data base and more extensive experience with a particular pest. In an advanced pest manage­ ment system, a computer processes region-wide data on pest population levels, host abundance and detailed environmental data. Simulation models are used to predict infestation levels and project results to be expected from alternative courses of action and the cost/benefit of each. Output from the computer models forms the basis for making improved decision (Coster 1980).

Regardless of the system's level of sophistication, the ultimate decision in most routine pest situations lies with the forest manager. His decision to control or not control and his choice of tactics are based on information provided to him by the decision support system or pest specialist, his own experience, and other extenuating circumstances (Cameron 1981).

Ideally, unexpected outbreaks and unanticipated losses are avoided by considering potential pest problems in the development of long range forest management plans. We should recognize that may of today's pest problems are the direct result of yesterday's forest management decisions. For example, the severe southern pine beetle outbreak in East Texas from 1973-77 has been attributed to overcrowded stand conditions associated with an 85% increase in pine sawtimber volume from 1955-75 (Hedden 1978). Control efforts were ham­ pered by wet ground conditions and insufficient access to infested stands;

113 114 as a result over 50 million cubic feet of timber were killed in 1976 alone and only half was salvaged (Texas Forest Service 1978). Had this outbreak been forecasted several years in advance, perhaps harvesting schedules could have been modified to reduce the abundance of susceptible host type. At the very minimum, access roads could have been constructed prior to the outbreak to accommodate the recovery of beetle-killed timber.

In another example, the decision some 10-15 years ago to plant large acreages in slash pine in Louisiana and Texas has resulted in the severe levels of fusiform rust infections we face today. Unfortunately, we still seem to make decisions with little consideration for their potential impact on pest populations. (Selecting large acreages of overmature pine stands in the South to preserve as wilderness immediately comes to mind as our most recent unwise decision). Foresters should continually ask themselves "Are my management practices today creating a pest problem for tomorrow?"

IFPM involves an integration of all suitable control strategies and tactics, including no control if circumstances warrant. Emphasis is placed on hazard rating and prevention (Bryant 1984) but direct control, including judi­ cious use of insecticides, remains a viable option. Control decisions are based on an economic damage threshold, and not necessarily on the mere presence of the pest. Direct control is only undertaken when the economic, social, and political benefits exceed the costs.

The Texas Forest Service approach to southern pine beetle control is an example of how approaches to a major forest pest are changing from "crisis response" toward one of integrated pest management. Major accomplishments have resulted from the cooperative efforts of field foresters, pest management specialists, and state, university and federal research workers.

In 1973, the Texas Forest Service developed a computerized system for recording all SPB detection, ground check and control records, the first of its kind in the South (Pase and Fagala 1979). This "Operations Informational System" relies upon the voluntary cooperation of Texas Forest Service and all major forest industries to submit field information on beetle infestations (spots). The input data on spot location, size, ownership, and control status is entered into one central data bank from which biweekly printouts are gen­ erated. These printouts are distributed to field personnel and their adminstra- tors to facilitate communication within and between participating organiza­ tions. The end-of-the-year data bank also has proved useful as a basis for evaluating area-wide infestation trends, the effectiveness of control tactics, and validation of SPB hazard and risk rating systems. A similar computerized SPB data management system has recently been implemented on the National Forests (M. Conner, USFS S&PF, personal communication).

During the 1970's, salvage and a new control method known as cut-and-leave (Billings 1980), rather than insecticides, were relied upon to treat inesta- tions as they occurred. From 1974—1985, two consecutive southwide USDA pro­ grams, the Expanded Southern Pine Beetle Research and Applications Program (ESPRAP) and the Integrated Pest Management Program For Bark Beetle of Southern Pines (IPM Program) focused on the southern pine beetle and related pests. These programs have greatly increased our knowledge of the beetle and have led to the development of improved methods for prediction, evaluation, suppression and prevention of beetle outbreaks (Thatcher et al. 1980, Payne et al. 1984).

115 In 1980, with financial support from the IPM program, the Texas Forest Service established a demonstration project in Polk and Tyler counties, two of the most beetle-prone counties in East Texas. The project goal was to imple­ ment, demonstrate and validate new technology for the integrated management of southern pine beetle. A landowner Advisory Board consisting of members from all major forest Industries in the area and the Texas Forest Service Area Forester provided guidance for project activities. Among project accomplish­ ments, all pine stands in the two county area (over 1 million acres) were delineated on aerial photographs and hazard rated (Bryant 1984). Hazard maps and lists of high hazard stands were provided to each industrial landowner to encourage hazard reduction. Many of the stands identified as high or extreme hazard have since been thinned or harvested. Foresters and landowners in the area were advised of available technology for beetle management through numer­ ous training sessions, newsletters, tours and publications. To date, despite high levels of beetle Infestations in adjacent counties, Polk and Tyler counties have remained relatively uninfested (Texas Forest Service 1984).

The Texas Forest Service grid block hazard rating system deserves mention because it has become the basis for our present SPB pest management system. Using computerized historical records for the period 1974-77 and 1974 aerial photography, the TFS Pest Control Section developed a method for rating TFS grid blocks (18,000 acre units) for SPB hazard (Billings and Bryant 1983). The system ranks grid blocks as high, moderate or low hazard to SPB, based on site/stand factors sampled from 1:120,000 scale color infra-red photography. Once developed and validated with additional historical records, the hazard rating system was applied to 656 grid blocks covering 11.8 million acres in Texas, using current (1981-3) aerial photography. The result is an area-wide hazard map showing where outbreak populations of the beetle are most likely to develop in East Texas. With this system, we were able to predict the recent shift in beetle activity from southeast Texas to the National Forests situated in central and western fringe counties of the pine zone. During 1982-84, for example, grid blocks rated high, moderate, and low hazard based solely on host abundance supported 62, 20 and 7 infestations per grid block, respectively.

Prior to the 1984 beetle season, the hazard rating system was further refined by combining hazard classes with recent infestation records to produce a SPB rish rating (very low, low, moderate, high and extreme risk) for each grid block. A list of grid blocks for all of East Texas by risk class was distributed to cooperating industries, the U.S. Forest Service and Texas Forest Service field offices early in 1984. The prognostication of risk has proven relatively accurate. By the end of the 1984 season, mean infestations per grid block were 89 in extreme risk, 17 in moderate risk, 11 in low risk and less than 4 in very low risk grid blocks. Industry foresters have found the system useful for identifying areas where control should be emphasized and where harvest and silvicultural operations are most needed. Once high hazard grid blocks are identified, individual pine stands within these grid blocks can be delineated and hazard rated in greater detail (Bryant 1984). The abundance of favorable habitats for the beetle is being reduced via silvicultural manipulations or harvest cuts as an integral part of long-range forest management planning. We plan to up-date and distribute the risk ratings annually prior to each beetle season. The hazard classifications, in turn, will be revised less frequently—probably every 5-6 years of photography is available.

116 Once infestations occur, improved methods are being used to make more intelligent control decisions (Thatcher et al. 1982). Priorities for ground check and control are placed on those infestations most likely to cause addi­ tional timber losses following detection (Billings 1979, Billings and Pase 1979). Beginning this year, non-industrial landowners notified of a beetle infestation detected on their lands also will receive an estimate of additional timber losses to expect if control is delayed (Billings and Hynum 1980). Although salvage and cut-and-leave remain the only control methods currently recommended, no action is being suggested as an alternative in low priority infestations likely to soon become inactive. On marginal spots or those in environmentally-sensitive areas, computerized decision support systems and mechanistic spot growth models are available to improve decision making (see article by R.N. Coulson, this symposium). The USDA Integrated Pest Management Decision Key (Anderson et al. 1985) - a set of four "user-friendly" micro­ computer programs - has proven useful for selecting appropriate management options for a complex of forest pests, Including SPB, fusiform rust, annosus root rot, brown spot disease, and pales weevil.

Clearly, in the case of most forest pests, pest management has become more than a one man job. A team approach, involving the forester, entomologist, pathologist, modeler, silviculturalist, economist, and other specialists, is needed to develop and maintain practical pest management systems. But, ulti­ mately, it is the man in the field—the forester of landowner—who is responsi­ ble for implementing more effective means of detection, evaluation, suppression or prevention of pests. By incorporating pest management considerations into his long-range forest management plans, and relying on specialists and com- puted-based decision support where needed, the forest should be able to meet his management objectives with the least disruption from insects, diseases, weeds, animals or other pests. And with powerful tools such as computers to process useful information from a variety of sources, pest management support personnel are in a better position to make reliable recommendations to the forester while keeping him abreast of changing trends in host abundance and pest population levels. In other words, if pest management is to serve our needs, we the protection specialists and you the foresters must all work together to make it happen.

Literature Cited

Anderson, R.L., R.P. Belanger, W.H. Hoffard, P. Mistretta, R.U. Uhler, and H.D. Brown. 1985. Integrated pest management decision key - four micro­ computer programs. J. For. 83:167.

Bennett, W.H. 1965. Silvicultural control of southern forest insects. Proc. 14th Annu. For. Symp., La. State Univ. Press, Baton Rouge, p. 51-59.

Billings, R.F. 1979. Detecting and aerially evaluating southern pine beetle outbreack. South. J. Appl. For. 3:50-54.

Billings, R.F. 1980. Direct control, p. 179-192. In, R.C. Thatcher, J.L. Searcy, J.E. Coster, and G.D. Hertel, eds. The southern pine beetle. USDA For. Serv. Sci. and Educ. Admin. Tech. Bull. 1631. 226 p.

117 Billings, R.F. 1984. Forest pests in East Texas: past approaches, future challenges. Proc. 10th Anniv. East Texas For. Entomol. Seminar. Texas Agric. Exp. Sta. MP 1553:1-5.

Billings, R.F, and C.M. Bryant. 1983. Developing a system for mapping the distribution of southern pine beetle habitats in east Texas. Z. angew. Entomol. 96:208-216.

Billings, R.F., and B.G. Hynum. 1980. Southern pine beetle: guide for predicting timber losses from expanding spots in East Texas. Texas For. Serv. Circ. 249. 2 p.

Billings, R.F., and H.A. Pase III. 1979. A field guide for ground checking southern pine beetle spots. USDA Agric. Handb. 558. 19 p.

Branham, S.J., and G.D. Hertel, eds. 1984. Proc. Integrated Forest Pest Management Symposium. Univ. of Ga. Center for Contin. Educ., Athens. 281 P*

Bryant, C.M. 1984. Hazard rating systems aid southern pine beetle prevention in Texas. Proc. Southern Silvicultural Res. Conf., Atlanta, Ga. (In press).

Cameron, R.S. 1981. Toward insect pest management in southern pine seed orchards. Texas For. Serv. Publ. 126. 149 p.

Coster, J.E. 1980. Developing integrated management strategies, p. 195-203. In, R.C. Thatcher, J.L. Searcy, J.E. Coster, and G.D. Hertel, eds. The southern pine beetle. USDA For. Serv. Sci. and Educ. Admin. Tech. Bull. 1631. 266 p.

Hedden, R.L. 1978. The need for intensive forest management to reduce south­ ern pine beetle activity in East Texas. South. J. Appl. For. 2:19-22.

Hedden, R.L., S.J. Barras, and J.E. Coster, eds. 1981. Hazard-rating systems in forest insect pest management. Symp. Proc. USDA For. Serv. Gen Tech. Rep. WO-27. 169 p.

Pase H.A., and E.P. Fagala. 1979. A computer-based informational system to aid southern pine beetle control operations. Texas For. Serv. Publ. 120. 21 p.

Payne, T.L., R.F. Billings, R.N. Coulson, and D.L. Kulhavy, eds. 1984. Proc. 10th Anniv. East Texas For. Entomol. Seminar. Texas Agric. Exp. Sta. MP 1553. 72 p.

Skove, D.J. 1984. Texas forest resource: harvest trends 1983. Texas For. Serv. Publ. 137. 19 p.

Texas Forest Service. 1978. Texas forest pest activity 1976-77 and Forest Pest Control Section biennial report. Texas For. Serv. Publ. 117. 28 p.

118 Texas Forest Service. 1984. Texas forest pest report 1982-1983. Texas For. Serv. Publ. 136. 31 p.

Thatcher, R.C., J.L. Searcy, J.E. Coster, and G.D. Hertel, eds. 1980. The southern pine beetle. USDA For. Serv. Sci. and Educ. Admin. Tech. Bull. 1631. 266 p.

Thatcher, R.C., G.N. Mason, G.D. Hertel, and J.L. Searcy. 1982. Detecting and controlling the southern pine beetle. South. J. Appl. For. 6:153-159.

Warren, L.O. 1965. Controlling insect damage to young southern pine. Proc. 14th Annu. For. Symp., La. State Univ. Press, Baton Rouge, p. 8-100.

Williamson, L. 1965. Controlling insect damage to merchantable southern pine. Proc. 14th Annu. For. Symp., La. State Univ. Press, Baton Rouge, p. 103-109.

119 MAKING MANAGEMENT DECISIONS BEFORE ESTABLISHING SLASH PINE PLANTATIONS IN AREAS WHERE FUSIFORM RUST IS A HAZARD

Warren L. Nance Principal Plant Geneticist Southern Forest Experiment Station P.O. Box 2008, GMF Gulfport, MS 39505

Yield prediction systems are essential to forest managers because they allow them to evaluate the effects of various management practices on the growth and yield of forest stands. By comparing the expected yield benefits and the costs of implementation for a variety of management alternatives, the forest manager can develop a management strategy that is optimum for his particular operation.

In many areas of the Southern United States, the process of developing economic management strategies is complicated by the presence of fusiform rust (Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme). This disease is Widespread throughout the region and typically infects young plantations of slash pine (Pinus elliottii Engelm. var. elliottii) and loblolly pine (Pinus taeda L.). Infected trees (particularly stem-infected trees) as group do not survive or grow as well as their uninfected neighbors in the same stand. As a result, most yield prediction systems (which were developed for healthy, uninfected stands) cannot be applied with confidence to infected plantations.

In this paper, a newly developed growth and yield prediction system (or model) for rust-infected slash pine plantations is discussed, with special emphasis on the use of the model to evaluate management alternatives that are available before plantations are established.

Modeling Background

The original form of the plantation yield system was described in Dell and others (1979) and Feduccia and others (1979). This modeling work, which involved both slash and loblolly pine growing in plantations essentially free of fusiform rust, was implemented in a computer program called USLYCOWG (£nthinned _Slash and Loblolly Yields for Cutover sites in the Western Gulf).

The USLYCOWG Model

The USLYCOWG prediction system can be briefly described in functional form as follows. For an unthinned plantation* (slash or loblolly pine), it is assumed that predictions of current yield (Y) can be generated using only three parameters: the age of the plantation in years (Ap), the number of living trees at that age (T^), and the mean height of dominant and codominant trees in the plantation at that age (Hp). In functional form this appears as

Y = Function (H^, TL » Ap ) . (1)

This form is concerned with predicting current yields, not with fore­ casting future yields, because both H^ and T^ must be known at the age of

1 2 0 interest, A . However, if predicted values for H_ and T^(symbolized by IL and Tt at age Ap are substituted in place of the known values, the resulting rorm L p

Y = Function (Hjj, TL> Ap) (2) can be used to forecast yields.

In the case of 1L, predicted heights can be generated if one has an estimate of the site index (S^) of the planting site—obtained from either soil-site relationships or the performance of previous or nearby stands. The predicted mean dominant and codominant height in this case appears as

Hp = Function(Sj, (3)

In the case of survival, predicted values can be generated using a sur­ vival function that requires one to know site index, the number of trees initially planted on the site (T ), and the plantation age; thus,

Tt = Function(ST, T , A ). (4) L I p p

Hence, in the forecasting mode the USLYCOWG system simply replace known values of IL and T with predicted values generated by appropriate prediction equations, and the resulting functional form for forecasting yields appears as

Y = Function(ST, T , A ). (5) I p p

Modifications Required in the Slash Pine Model for Fusiform Rust

The basic approach in incorporating fusiform rust into the USLYCOWG slash pine model was to: (1) acquire a large data base generated by long-term growth and yield type studies in which fusiform rust infection had been closely monitored, (2) determine which components of the original slash pine model required modifications for fusiform rust, (3) accomplish the required modi­ fications, (4) integrate the new components into the USLYCOWG system, and (5) provide and enhanced user interface to the new system.

Slash pine data base

Two large, long-term experiments generated the data used in this modeling work. The first experiment, designated as set A, was originally designed to compare the growth and yield of loblolly, slash, and longleaf pines on diverse sites (Shoulder 1976, Shoulders and Walker 1979, and Nance and others 1981). The plots in his study were examined and measured periodically for rust infec­ tion and growth for 20 years. The slash pine data from this study involved 100 plots from Mississippi and 87 plots from Louisiana. There were 64 planted trees in the interior of each Mississippi plot and 49 in each of the Louisiana plots. Site indexes at base age 25 (estimated from an equation presented by Dell and other 1979), ranged from 25 to 80 feet, with a mean of 62 feet.

1 2 1 Planting density (number of trees planted per acre) was 1,210 for all plots, with the number of trees surviving at plantation age 5 (T^) ranging from 600 to 1,210 trees per acre, with a mean of 996. The percentage of living trees with a stem canker at age 5 (S_) ranged from 0 to 32, with a mean of 4, and the cumulative percentage of trees that died with a stem canker by age 20 ranged from 0 to 44, with a mean of 14.

The second experiment, designated as set B, was installed by a large industrial forestry firm to compare the growth and yield of slash and loblolly pine planted on a wide array of sites. The study plots were examined and measured periodically for rust infection and growth for 17 years. The slash pine data from this experiment involved 281 plots from Alabama, Georgia, Florida, and South Carolina. There were 25 measured trees in each plot, with site indexes at base age 25 (estimated as in set A) ranging from 25 to 78 feet, with a mean of 54 feet. Planting density ranged from 100 to 1,100 and estab­ lishment densities from 80 to 1,000 trees per acre, with a mean of 406. The percentage of living trees with a stem canker at age 5 ranged from 0 to 76, with a mean of 18. The cumulative percentage of trees that died with a stem canker present by age 17 ranged from 0 to 78, with a mean of 21.

Predicting future survival of stands

Previous work by Nance and others (1981) detailed some of the effects (derived from the slash pine data base) of fusiform rust on the growth and development of slash pine plantations. Briefly, slash pines that developed fusiform rust stem cankers by age 5 were found to have a much higher probability of death in later years than their rust-free neighbors. Surpris­ ingly, however, trees that survived with stem cankers to later ages appeared to compete and grow as well over time as their uninfected neighbors.

The observations on individual-tree growth and survival were reinforced and confirmed by two fundamental modeling results (Nance and others 1982). The first result was that the basic assumption underlying the USLYCOWG system—that current yield in an unthinned slash pine stand is simply a function of T^ and Hp—was also valid for rust-infected stands that had undergone natural thinning from fusiform rust. Table 1 presents, for comparison, observed volumes and quadratic mean diameters in data sets A and B and those predicted by the original USLYCOWG system when used with the observed and T^ values for these rust-infected plots.

The second result was that future survival for both infected and unin­ fected stands could be predicted if a rust level variable were incorporated into the survival function. The specific form of the survival function developed as a replacement for (4) was

\ ’ [T5_B ^ ~51+1] 1 (1_S5) " B ^ " 5]l * (6) where Bj and B„ are coefficients to be estimated. Note that this form does not require S^, which is partly a consequence of using T_ instead of T as the primary density variable. Mortality before plantation age 5 is oftenPstrongly related to site quality, while mortality after age 5 shows a much weaker relationship to site quality. Table 2 presents, for comparison, observed and predicted survival for data sets A and B when using this survival function.

1 2 2 Table 1. Comparison of observed and predicted volumes and quadratic mean diameters for two data sets using H_ and T. values at age 17 or 20 as input to USLYCOWG L

Data No. Variable 2/ base Age plots predicted ri/ Bias—

yrs %

SET A 20 187 V o l u m e ^ 0.91 2.18 4/ 20 187 QMDBH-1' 0.90 1.33

SET B 17 281 Volume 0.98 4.12

17 281 QMDBH 0.91 4.45

— r denotes the simple correlation between observed and predicted values of the response variable. 2 / — Bias % = ((predicted - observed)/observed) x 100. 3/ 2 — Volume = 0.0339 + 0.0026 (d.b.h. x Height) for all trees (Moehring and others 1973). 4/ — QMDBH = quadratic mean d.b.h., or the d.b.h. of the tree with average basal area.

Integration of the modified survival model

Because the survival function was the only component of the original USLYCOWG slash pine model that required modification, it was a relatively simple task to delete the old survival subroutine and insert a new one in its place. Functionally, this replacement produces the final form

Y = Function(ST, Tc, Sc, A ), (7) I 5 5 p which allows the forecasting of yields for infected plantations established at age 5 with known rust level, establishment density at age 5, and site index.

Development of an enhanced user interface

We felt that the original USLYCOWG system was not particularly easy to use nor easily accessible to most potential users. The program was not interac-

123 Table 2. Observed and predicted survival using for all measurement ages.

Data 2/ 4/ Model base Observations^ r— B i a s ^ Std. error- B 1 B 2

No. %

s — Set A 561 0.0031113 -0.1038100 0.71 -0.10 125

Set B 1,124 0.0010951 -0.0841180 0.99 -2.60 38

Sets A+B 1 ,685 0.0025306 -0.0712972 0.96 -0.50 84

— For set A, based on measurements at ages 10, 15 , and 20 for 187 plots, and for set B based on ages, 8, 11, 14, and 17 for 281 plots. 2/ — 4 = simple correlation between observed and predicted number of surviving trees per acre. 3/ — Bias = (predicted survival - observed survival) x 100. observed survival 4/ Std. error = standard deviation of (observed — predicted) survival in trees per acre units.

— Sj = the proportion of trees living at age 5 with a stem canker. tive, was not accessible via dial-up facilities, and could not be executed on microcomputers. To correct these deficiencies in the rust version, the program was rewritten.

Once this was accomplished, it was possible to allow a large number of users to access the new model via dial-up telephone lines, run the system interactively, and provide feedback regarding improvements that could be made to the system. This feedback mechanism provided many valuable suggestions, all of which were eventually incorporated into the rust model. This model has been converted to the FORTRAN 77 language and is compatible with most computer systems (including microcomputers).

The Slash Pine Rust Model

The current version of the slash pine system is primarily designed to accept inputs that describe a newly established slash pine plantation and then project future yields for that plantation for any age up to age 20. The four basic input variables accepted are: T , the number of trees living at age 5; S^, the proportion of living trees at age 5 that have a fusiform rust stem canker; S , the site index of the planting site; and A , the plantation age for which a stand table projection is desired. p

124 Given the basic input variables, the model projects survival and yield by diameter class to any user—specified projection age up to 20, assuming there are no thinnings. Additional user inputs are allowed for specification or merchantability limits such as stump height, limiting top diameter, and minimum acceptable diameter at breast height (d.b.h.).

Figure 1 shows the menu displayed by the program. The top half of the menu (labeled "RANGE OF APPLICATION") shows the basic input variables that control the number and type of stand tables subsequently generated by the program. The column labeled "KEY" contains a two-letter abbreviation for each variable in the menu. In the following discussion, the key, rather than the full description, is used to refer to input variables.

Because most users want to generate an array of stand tables rather than a single table, the four input variables under the heading "PRIMARY VARIABLES" are assigned a range of values rather than a single value. The range is controlled by the "FIRST", "LAST", AND "STEP" values assigned by the user for each of the primary variables—SI, T5, S5, and PA. The program begins execu­ tion with the primary variable equal to FIRST, then increments the variable to a new value equal to FIRST+STEP, and continued this process until the variable exceeds LAST is set equal to FIRST, and STEP is set equal to one. This simply defines a range of one value for each of the primary variables.

If, for example, the user sets FIRST, LAST, and STEP values equal to 50, 70, and 10 for SI, then upon execution the program will generate stand tables for site indexes of 50, 60, and 70. The values for the other three primary variables could also take on many different values at the same time, multiply­ ing the total number of stands that would be generated. , For example, if the user changes the input menu to appear as follows:

KEYFIRSTLAST STEP

SI 50 70 10 T5 800 1,000 100 S5 10 50 10 PA 15 20 5 the program will generate 90 stand tables (3 x 3 x 5 x 2), with the first stand table projected at age 15 for a plantation established on a site having a site index of 50 (index age 25), with 800 trees per acre living at age 5, and with 10 percent of those trees infected with stem cankers.

The two remaining variables listed under "RANGE OF APPLICATION", IA and C5, can only take on a single value and hence do not actually affect the number of stand tables generated. The first (IA) simply allows the user to define an index age for site index. Slash pine site indexes are normally based on plantation age 25, which is the default value assigned to IA in the initial menu. The variable C5 allows the user to specify a comparison level for percentage of stem infection. For each set of SI, T5, S5, and PA values, the program automatically generates a comparison stand with the same SI, T5, and PA but uses C5 instead of S5 for the rust variable. The two stand tables are then compared automatically, and the results are printed along with the stand table. The process is repeated for all combinations of SI, T5, S5, and PA values

125 defined by the menu. Initially, a default value of zero is assigned to C5, which provides comparisons with rust-free stands.

The bottom half of Figure 1 (labeled "VOLUME SPECIFICATION") allows the user strict control of volume computations for each stand table. The left half of the volume specification menu controls volumes that are computed by stem profile equations, an the right half controls volume computed by equations based on d.b.h. squared times total height (DSQH). Given these inputs, the program computes merchantable volumes by diameter class using the stem profile model defined by Dell and others (1979).

Figure 1. Default menu for slash pine rust model.

YIELDS BY DIAMETER CLASSES FOR UNTHINNED SLASH PINE PLANTATIONS INFECTED WITH FUSIFORM RUST STEM CANKERS AT AGE 5 *****************************j^uGE OF APPLICATION****************************** ------PRIMARY VARIABLES------KEYFIRST LASTSTEP SITE' INDEX SI 70 70 1 TREES ESTABLISHED (AGE 5) T5 800 800 1 PERCENT STEMS RUST INFECTED (AGE 5) S5 60 60 1 PROJECTED PLANTATION AGE (YEARS) PA 20 20 1 ------ADDITIONAL VARIABLES------KEY VALUE INDEX AGE FOR SITE INDEX IA 25 S5 FOR COMPARISON C5 0 ******************************VOLUME SPECIFICATION***************************** FROM STEM PROFILE * FROM DSQH EQUATION ITEM KEY VALUE * ITEM KEY VALUE * MIN DBH CLASS MD 4 * MIN DBH CLASS MC 0 TOP LIMIT DIAMETER (INCHES) TD 3 * INTERCEPT BZ 0.033900 TD OUTSIDE OR INSIDE BARK? 01 0B * LINEAR Bl 0.002646 STUMP HEIGHT (FEET) SH 0.5 * QUADRATIC B2 0.000000 ******************************************************************************* *** Available commands are HELP, DISPLAY, FULL, BRIEF, RUN, AND STOP *** *** Type HELP INPUT for help on changing values in this input menu COMMAND?

The DSQH variables include MC, BZ, Bl, and B2. The variable MC is equiva­ lent to the stem profile variable MD and simply defines the minimum acceptable d.b.h. The variables BZ, Bl, and B2 define the coefficients to be used in the following quadratic equation:

V = BZ + Bl(DSQH) + B2(DSQH*DSQH) where

V = volume (or perhaps dry weight), BZ = intercept term, Bl = linear coefficient of DSQH, and B2 = quadratic coefficient of DSQH.

By setting B2 equal to zero, the user can force a simple linear regression model for volume equations based on DSQH. Typical default values for slash

126 pine are initialized in the menu, but most users prefer to use their own local values instead.

The value for any variable in the menu can be changed easily by the user. In response to the "COMMAND?" prompt, the user types the key letters and the new values

SI = 50,70,10.

This statement redefines FIRST, LAST, and STEP values for site index to 50,70, and 10 respectively. Typing DISPLAY in response to the command prompt will display (or print, if the terminal is a hardcopy device) a new menu containing the current values for all input variables. Once no more changes to the input menu are desired, typing RUN causes the program to generate stand tables prescribed by the menu. Typing FULL before typing RUN directs the program to print the full stand table. If full output is not desired, typing BRIEF before RUN causes another menu to appear, from which the user can select the particular stand summary information to be printed. BRIEF output is much more compact than FULL and is preferable when generating more than a few stand tables. The program also allows a HELP command that provides information regarding the operation of the program.

Figure 2 is a copy of the FULL printout generated by the menu shown in Figure 1. Most of the output is self explanatory, but the following cryptic abbreviations may not be obvious:

Abbreviation ______Meaning

AV. D+C HT. average height of dominant and co-dominant trees CR average crown ratio AV. HT. average height of all trees 0.B. outside bark 1.B. inside bark AP plantation age, same as PA D2H d.b.h. x d.b.h. x total height, same as DSQH A, B, C the shape, scale, and location parameters of the Weibull distribution function used to represent the diameter distribution of the current stand table.

The top section (labeled "STAND TABLE") contains predicted values for each 1—inch diameter class. The lower half (labeled "MORE DETAILS ON RUST COMPARISON") contains several stand summary statistics that are compared for the two stands with rust levels equal to S5 and C5. The comparison between C5 and S5 is highlighted throughout the output.

Application of the Slash Pine Model

The three primary variables (T5, S5, and SI) must be specified in order to generate predicted yields. For any plantation observable at age 5, one can utilize a suitable sampling scheme to obtain estimates of the number of living trees per acre (T5), as well as the proportion of those trees with stem galls (S5). However, the site index of the established site is more difficult to estimate. Experience has shown that the height of trees at age 5 is a poor predictor of mean dominant—codominant height in future years, so it is recom—

127 Figure 2. Stand table output generated by slash pine rust model with default input values.

— YIELDS BY'd IAMETER CLASSES FOR AN UNTHINNED SLASH PINE PLANTATION OF GIVEN AGE (AP), SITE INDEX (SI), TREES LIVING AT AGE 5 (T5), AND PERCENT OF LIVING TREES INFECTED WITH FUSIFORM RUST STEM CANKERS AT AGE 5 (S5) *********************************STAND TABLE*********************************** INCLUDES COMPARISONS TO A REFERENCES PLANTATION WITH A DIFFERENT RUST LEVEL (S5) BUT THE SAME VALUES FOR AP, SI, AND T5

SITE INDEX 70 (BASE AGE 25'*

AGE --- CUBIC FOOT VOLUME--- MERCHANTABLE TREES GROWING ALL TREES >= 4 IN. DBH CLASS SEASONS AV. TREES BASAL GROUND FROM 0.5 FT. STUMP IN D+C DBH PERAREA/ CR AV. TO TIP TO 3.0 IN. OB TOP FIELD HT.CLASS ACRE ACRE HT. O.B. I.B. O.B. I.B. •k'k'k'k'k'k'k ******** ***** ***** •kielc **** **** ****

20 60 4 2 0.2 34 33 4 2 3 2 5 8 1.1 37 41 25 16 21 14

6 21 4.1 40 47 108 73 97 67 7 41 11.0 42 52 315 221 293 208 8 60 20.9 44 56 645 462 607 439 9 57 25.2 46 60 825 600 783 575 10 33 18.0 47 63 615 453 587 436

11 10 6.6 49 65 231 172 221 166 12 1 0.8 50 67 28 21 27 20 ----- TOTALS------FOR S5 = 60% 233 87.9 2796 2020 2639 1927 IF S5 = 0% 621 158.1 4933 3488 4561 3268 DIFFERENCE -388 -70.2 -2137 -1468 -1922 -1341 % DIFFERENCE -43 -42 -41 -41 -40 ************************* MORE d e t a i l s o n r u s t c o m p a r i s o n *********************

S5 = 60% S5 = 0% % DIFFERENCE *********** ********** ************

***SURVIVAL AND RUST*** NUMBER OF LIVING TREES AT AGE 5 (T5) 800 800 PERCENT STEMS RUST INFECTED AT AGE 5 (S5) 60 0 PERCENT SURVIVAL AT AP = 20 ------29 78 -49

***DBH AND CROWN RATIO*** MEAN CROWN RATIO (ALL TREES) 44 34 10 ARITH, MEAN DBH------8.2 6.6 23 QUADRATIC MEAN DBH------8.3 6.8 22

***DSQH VOLUME PER ACRE (DBH CLASSES >= 0)*** SUM OF DSQUARED H ------937514. 1686294. -43 VOLUME: USING 0.033900 + 0.002646 * D2H + 0.000000 * D2H * D2H ----- 2489. 4483. -43

***WEIBULL PARAMETERS***

A 1.55 1.08 44 B 7.21 6.14 17 C 5.10 4.06 26

128 mended that estimates of site Index be based on concomitant Information such as soil-site predictors or perhaps site index estimates for former or present nearby slash pine stands. Once estimates of T5, S5, and SI are obtained, the program can be used to generate expected yields at any future age up to age 20, assuming there are no thinnings. The predicted yields could then be combined with economic data to help the manager make decisions regarding the management of that particular plantation.

Although the model can be used in the manner described above, it is perhaps more valuable to the manager when used to simulate yields. In this way, the user assigns a range of values to T5, S5, and SI; generates the predicted yields for these values; and then combines the yield information with economic data to help him make decisions regarding the establishment and management of new slash pine plantations in his particular operation.

A Hypothetical Problem For Slash Pine Management

A simplified example is offered to illustrate one way in which the model simulations of pine yields might be used to aid in pre-planting decisions. In this example, total cubic foot volume is the only production unit considered (economic data on costs and returns will not be considered), and the range of alternatives to be considered is severely restricted.

The problem

A manager has to plant 3,000 acres with slash pine seedlings. Half the land is of good quality, having a site index of 50. Sites of both good and poorer quality are evenly distributed throughout the 3,000 acres. Fusiform rust presents a high hazard (S5 = 70%) to 1,000 acres, a medium hazard (S5 = 30%) to 1,000 acres, and a low hazard (S5 = 10%) to 1,000 acres. The dis­ tribution of sites is:

Site category SI S5 Acreage 1 70 50 500 2 70 30 500 3 , 70 10 500 4 50 50 500 5 50 30 500 6 50 10 500

The manager normally plants 750 trees per acre and achieves, on the average, an establishment density of 500 trees per acre. Unimproved planting stock is typically used. The manager generally waits until about age 15 before considering thinning and other management options. The manager wants to know: (1) the expected volume losses (relative to when S, = 0) due to fusiform rust if he establishes the planting sites in the normal way, (2) the alternatives available to reduce the volume losses, and (3) the amount of the volume loss.

Available management alternatives

Many alternatives could be considered with the current model, but only three will be examined in this case. Alternative A would establish the plan­ tations in the normal way using unimproved planting stock and a planting density of 750 trees per acre. Alternative B would increase the planting

129 density with unimproved stock to compensate for the increased mortality due to fusiform rust. Alternative C would use resistant planting stock (the planting density could be changed at the same time).

Assessment of alternative A

Table 3 summarizes the expected total volumes per acre for the six site categories and the expected volume loss due to fusiform rust under this manage­ ment option. About half of the expected volume losses are confined to sites of index 70, with S5 equal to 50 percent, and almost three-fourths of the expected volume losses occur on sites where the site index is 70. Considering the total acreage, this alternative has an expected volume at age 15 of about 5,158,500 cubic feet, and 795,000 cubic feet are expected to be lost due to fusiform rust.

Table 3. Expected total volumes (per acre, outside bark) and volume losses due to fusiform rust at age 15 for management alternative A.

Site Assumed values Expected Assumed values Expected Expected loss category SI S5 T5 volume SI S5 T5 volume due to rust

--- With fusiform rust------Without fusiform rust------Loss ------

ft % t/a ft3 ft % t/a ft3 ft3 %

1 70 50 500 2,030 70 0 500 2,735 705 25 £.o 70 30 500 2,372 70 0 500 2,735 363 12 3 70 10 500 2,631 70 0 500 2,735 104 3

4 50 50 500 988 50 0 500 1,234 246 19 5 50 50 500 1,109 50 0 500 1,234 125 9 6 50 10 500 1,187 50 0 500 1,234 47 3

Mean per acre 1,720 1,984 265 13

Assessment of alternative B

Two simple variations of this alternative were considered. The first, option 1, is to simply choose a uniformly higher planting density for all site categories in order to lower the overall expected volume losses and achieve some target goal. Option 2 is to allow different planting densities for each site category in an attempt to reach the same target goal. In both options, the target goal for this example is to produce 5,953,500 cubic feet of total volume for the 3,000 acres. This is the expected volume under management alternative A in the absence of rust.

To find a uniform planting density for all site categories that will produce the required volume, one can simply apply the program repeatedly for a range of T5 values until one is found that produces the desired volumes. The

130 following input values for the primary variable in the input menu was used to accomplish the task:

KEY FIRST LAST STEP

SI 50 70 20 T5 500 700 10 S5 10 50 20 PA 15 15 1

The values for SI and S5 define the range of site indexes and rust levels for the 6 site categories of interest, and the values for T5 define a range of 20 establishment densities to simulate for each category. The program output reveals that when T5 equals 660 trees per acre, the total volume over all 6 site categories is 5,943,500 cubic feet, which is within 10,000 cubic feet of the target volume. Table 4 contains a summary of the increase in volume by category for option 1. Assuming the same planting mortality rate as before (33 percent), an establishment density of 660 trees per acre translates to a required planting density of 990 trees per acre, or an increase of 240 trees per acre (or 720,000 trees for the 3,000 acres) in planting density compared to alternative A.

Table 4. Expected gains from uniformly increasing establishment density under management alternative B, option 1.

Site Assumed values Expected Assumed values Expected Expected loss category SI S5 T5 volume SI S5 T5 volume from higher T5 ----- With lower T5------With higher T5------Gain----

ft % t/a ft3 ft_ % t/a ft3 ft3 %

1 70 50 500 2,030 70 50 660 2,418 388 25 2 70 30 500 2,372 70 30 660 2,761 389 12 3 70 10 500 2,631 70 10 660 3,015 384 3

4 50 50 500 988 50 50 660 1,130 142 19 5 50 30 500 1,109 50 30 660 1,237 128 9 6 50 10 500 1,187 50 10 660 1,326 139 3

in per acre 1,720 1,981 262 13

Unfortunately, the regained volume under this strategy is not ideally distributed throughout the six site categories. For example, only about half of the expected losses in categories 1 and 4 (high hazard) would be regained with this option, while net increases over and above expected losses for categories 3 and 6 (low hazard) make up the difference. Only categories 2 and 5 (medium hazard) appear to be correctly adjusted by this approach.

The second option is perhaps more realistic, because it allows one to vary T5 for the different site categories in order to achieve the same goal. Repeated application of the program category by category results in the required T5 values for each category shown in Table 5. As expected, the required adjustment in T5 ranges from a small increase of only 40 established

131 trees per acre (or 60 planted trees per acre) for categories 3 and 6 to a large increase of 330 established trees per acre (or 495 planted trees per acre) for categories 1 and 4. Categories 2 and 5, as expected, were only slightly changed from the densities required in option 1.

Table 5. Expected gains from variable increases in establishment density under management alternative B, option 2.

Site Assumed values Expected Assumed values Expected Expected loss category SI S5 T5 volume SI S5 T5 volume from higher T5 ------With lower T5------With higher T5------Gain----

ft % t/a ft3 ft % t/a ft3 ft3 %

1 70 50 500 2,030 70 50 830 2,735 704 35 2 70 30 500 2,372 70 30 650 2,742 370 16 3 70 10 500 2,631 70 10 540 2,735 104 4

4 50 50 500 988 50 50 830 1,234 246 25 5 50 30 500 1,109 50 30 650 1,234 122 11 6 50 10 500 1,187 50 10 540 1,234 47 4

Mean per acre 1,720 1,985 266 15

Assessment of alternative C

The use of genetically resistant planting stock is currently the primary control measure for fusiform rust. In addition to lowering infection levels, improved stock offers the possible advantage of increased growth potential as well.

Two different types of improved stock are simulated in the alternative. Type 1 offers resistance without increased growth potential when compared to the unimproved stock assumed in management alternative A. The use of this stock would simply result in a 50 percent reduction in S5 values. Type 2 stock is assumed to offer both resistance and increased growth potential. This stock has the same resistance as type 1 stock (lowering S5 by 50 percent) and at the same time results in an increase in site index of 6 percent compared to unim­ proved stock on the same site.

Table 6 show the effect of using type 1 stock. About half of the expected losses under management alternative A would be regained under this option. As expected, the volume gains are not distributed equally over the six site categories—high hazard sites benefit much more from the use of the resistant stock than the other site categories.

Table 7 shows the additional effect of using type 2 stock, where the combination of resistance and growth rate resulted in an expected overall gain of 1,261,000 cubic feet over the 3,000 acres-—surpassing the amount needed to regain the expected volume loss under management alternative A for all six site categories. The total increase in expected volume for the 3,000 acres amounted to 466,000 cubic feet (or 155 cubic feet per acre).

132 Table 6. Expected gains from uniformly decreasing rust levels under management alternative C using resistant (type 1) planting stock.

Site Assumed values Expected Assumed values Expected Expected loss category SI S5 T5 volume SI S5 T5 volume from higher S5 ----- With higher S5------With lower S5------Gain----

ft % t/a ft3 ft % t/a ft3 ft3 %

1 70 50 500 2,030 70 25 500 2,441 411 20 2 70 30 500 2,372 70 15 500 2,572 200 8 3 70 10 500 2,631 70 5 500 2,689 58 2

4 50 50 500 988 50 25 500 1,133 145 15 5 50 30 500 1,109 50 15 500 1,178 69 6 6 50 10 500 1,187 50 5 500 1,208 21 2

n per acre 1,720 1,870 151 9

Table 7. Expected gains from uniformly decreasing rust levels and increasing site index under management alternative C using resistant (type 2) planting stock having increased growth potential.

Site Assumed values Expected Assumed values Expected Expected gain sgory SI S5 T5 volume SI S5 T5 volume higher T5, SI -With higher S5, lower Si­ -With lower S5, higher Si­ ----- Gain—

ft % t/a ft3 ft % t/a ft3 ft3 %

1 70 50 500 2,030 74 25 500 2,794 764 38 2 70 30 500 2,372 74 15 500 2,926 554 23 3 70 10 500 2,631 74 5 500 3,051 420 16

4 50 50 500 988 53 25 500 1,304 316 32 5 50 30 500 1,109 53 15 500 1,359 250 23 6 50 10 500 1,187 53 5 500 1,405 218 18

i per acre 1,720 2,140 420 24

Genetically improved stock tends to be both expensive and in short supply. It seems reasonable then to investigate alternatives that make better use of improved stock. In the above examples, 2.25 million improved seedlings would be required to plant 3,000 acres at 750 trees per acre. In this option, it is assumed that the supply of improved seedlings is limited to this number, but that they need not be deployed uniformly over all site categories at a constant planting density. Furthermore, it is assumed that unimproved stock is not to be planted in lieu of improved stock. The goal is to increase volumes over those attained with type 2 seedlings planted at a uniform density of 750 trees per acre simply by re-deploying the same material at variable densities for different site categories.

133 The assessment of this alternative can become quite complicated. So complicated, in fact, that one has little hope of reaching some sort of optimum solution without employing sophisticated mathematical techniques. Rather than resort to such complicated techniques, it suffices here to generate an alterna­ tive based on a simple idea.

The reasoning is as follows. Choose some minimum number of seedlings to be deployed as a group, say 25,000, and restrict their deployment to a single site category. This is enough seedlings to plant 50 trees per acre for any given site category. Next, compare the effect on volume when this number of trees per acre is added to the current planting rate for each site category in turn. Finally, allocate the group of 25,000 trees to the site category that would produce the highest volume increment resulting from the density increase. Applying this process repeatedly will eventually allocate the entire set of resistant seedlings to the various site categories.

Table 8 shows the deployment strategy arrived at by this process. The total volume expected from this deployment amounts to 6,795,000 cubic feet—a gain of 375,500 cubic feet (or 125 cubic feet per acre) compared to the uniform deployment of the same stock at 750 trees per acre across all sites. Hence, the gain achieved from this strategy nearly equals the gain achieved from the use of genetically improved stock in the first place.

Table 8. Expected gains from uniformly decreasing rust levels and increasing site index under management alternative C using resistant (type 2) planting stock having increased growth potential and variable plant­ ing densities.

Site Assumed values Expected Assumed values Expected Expected gain category SI S5 T5 volume SI S5 T5 volume higher T5, SI -With higher S5, lower SI- --With lower S5, higher Si­ ----- Gain------

ft % t/a ft3 ft % t/a ft3 ft3 % 1 74 25 500 2,794 74 25 800 3,537 743 27 2 74 15 500 2,926 74 15 750 3,579 653 22 3 74 5 500 3,051 74 5 700 3,617 566 19

4 53 25 500 1,304 53 25 300 1,007 -297 -23 5 53 15 500 1,359 53 15 250 956 -403 -30 6 53 5 500 1,405 53 5 200 894 -511 -36

Mean per acre 2,140 2,265 +125 + 6

Even more gain might be achieved if one relaxed the constraint on the use of unimproved stock. By deploying unimproved stock—either in mixtures with improved stock, or in pure plantations—it is possible that the improved stock could be more effectively utilized than with the deployment shown in table 8.

Conclusions

The somewhat simplistic approach taken here was designed merely to illus­ trate how managers might apply yield prediction systems in developing disease management strategies. Obviously, economic data must ultimately be incorporat­

134 ed in the process before economic decisions can be made. Also, a wider, and more complex, array of sites and alternative strategies need to be evaluated. For example, more complex, but yet more realistic, deployment strategies would include deployment of individual families, mixtures of certain families, and perhaps the use of unimproved stock in mixtures with various improved families.

Although the current version of the model presented here for slash pine is limited in the kinds of alternatives that can be addressed, it should still be useful to forest managers in helping to evaluate common alternatives such as manipulating planting density and deploying resistant planting stock. Hope­ fully, future enhancements to the system will allow forest managers to evaluate the kinds of complex management schemes that are required in intensive forestry.

Literature Cited

Dell, T.R., D.P. Feduccia, T.E. Campbell, W.F. Mann, Jr., and B.H. Polmer. 1979. Yields of unthinned slash pine plantations on cutover sites in the west Gulf region. Res. Pap. SO-147. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, 84 p.

Feduccia, D.P., T.R. Dell, W.F. Mann, Jr., T.E. Campbell, and B.H. Polmer. 1979. Yields of unthinned loblolly pine plantations on cutover sites in the west Gulf region. Res Pap. SO-148. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, 88 p.

Moehring, D.M., M.R. Holmes, and R.G. Merrifield. 1973. Tables for estimating cubic foot volume and fresh weight of planted slash pine. MP-1079. Texas A&M Univ., College Station, TX.

Nance, W.L., R.C. Froelich, and E. Shoulders. 1981. Effects of fusiform rust on survival and structure of Mississippi and Louisiana slash pine plan­ tations. Res. Pap. So-172. New Orleans, LA: &.S. Department of Agricul­ ture, Forest Service, Southern Forest Experiment Station, 11 p.

Nance, W.L., R.C. Froelich, T.R. Dell, and E. Shoulders. 1982. A growth and yield model for unthinned slash pine plantations infected with fusiform rust. In: Jones, Earle P., Jr., ed. Proceedings of the Second Biennial Southern Silvicultural Research Conferences; 1982 November 4-5; Atlanta GA. Gen. Tech. Rep. SE-24. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, 1982:275-282.

Shoulders, E. 1976. Site characteristics influence relative performance of loblolly and slash pine. Res. Pap. SO-115. New Orleans, LA: U.S. Depart­ ment of Agriculture, Forest Service, Southern Forest Experiment Station, 115 p.

Shoulders, E., and F.V. Walker. 1979. Soil, slope, and rainfall affect height and yield in 15-year-old southern pine plantations. Res. Pap. SO-153. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, 52 p.

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