PIN YO N PINE

Management Guidelines For Common Pests

JoAnne Skelly Extension Educator, Carson City/Storey County University of Nevada Cooperative Extension

John Christopherson Resource Management Officer, Nevada Division of For

EB-03-02

PIN YO N PINE

Management Guidelines For Common Pests

JoAnne Skelly

Extension Educator, Carson City/Storey County University of Nevada Cooperative Extension

John Christopherson Resource Management Officer, Nevada Division of Forestry

Funded in cooperation with the USDA Forest Service. This reprint was made possible with funds from an Assistance Agreement with the Bureau of Land Management and Storey County Fire Protection District in collaboration with University of Nevada Cooperative Extension.

Copyright © 2003, 2nd edition, 2nd printing 2016. University of Nevada Cooperative Extension is a partnership of Nevada counties; University of Nevada, Reno; and U. S. Department of Agriculture. The University of Nevada, Reno, Nevada Division of Forestry and the USDA Forest Service are equal opportunity affirmative action employers and do not discriminate on the basis of race, color, religion, sex, age, creed, national origin, veteran status, physical or mental disability, sexual orientation or genetic information in any program or activity they operate. The University of Nevada, Reno, Nevada Division of Forestry and USDA Forest Service employ only United States citizens and aliens lawfully authorized to work in the United States.

CONTENTS

Introduction and Description ...... 7

Keeping Trees Healthy ...... 9

Pinyon Forest Management Guidelines ...... 13

Common Pests ...... 15

Insects

Pinyon Ips Beetle ...... 15

Red Turpentine Beetle ...... 17

Twig Beetle ...... 19

Pinyon Needle Scale ...... 20

Pitch Mass Borer ...... 22

Pinyon Tip Moth ...... 23

Pinyon Sawfly ...... 24

Diseases

Black Stain Root Disease ...... 25

Pinyon Needle Rust ...... 26

Pinyon Blister Rust ...... 27

Pinyon Dwarf Mistletoe ...... 27

Conclusion ...... 31

Glossary ...... 33

References ...... 35

Photo Credits ...... 37

PINYON PINE Management Guidelines For Common Pests : 7

INTRODUCTION

inyon pine (Pinus monophylla) know how to take care of the native woodlands occur on many of pines. This guide will help homeown- thPe mountai n ranges of Nevada. ers identify and manage common With development spreading into pests of pinyon pine. The guide these woodlands, home landscapes discusses general practices to often include singleleaf pinyon. maintain healthy trees, lists specific Home-owners wishing to maintain pests, and outlines management these native landscapes need to strategies.

DESCRIPTION

ne of Nevada’s two state trees, conifer, taking as long as 60 years to singleleaf pinyon is also one of reach about 6.5 feet. However, it theO pr edominant trees in the Great typically grows from 2 to 4 inches per Basin, growing not only in Nevada, but year with mature trees reaching 20 also in parts of California, and feet to 40 feet, depending on the site western Utah. It tolerates drier quality. Its life span can be greater conditions better than other Nevada than 600 years. pines. In the drier portions of its range, it is often found in association Across its extensive range in the with Utah juniper (Juniperus osteosper- state, pinyon is important to wildlife, ma). It grows at elevations ranging providing food and cover for many from approximately 3,200 feet to species including birds and large and 9,200 feet. small mammals. Trees are also of considerable cultural value to Native Singleleaf pinyon is a slow growing Americans of the Great Basin.

PINYON PINE Management Guidelines For Common Pests : 9

KEEPING TREES HEALTHY

ealthy trees have fewer insect Constant irrigation can rot pinyon and disease problems than roots, causing diseases, branch tHrees that are stressed. It is impor- dieback, and death. tant to keep trees vigorous by reducing human-caused stress factors The pinyon’s growth, starting in April such as improper irrigation, construc- and ending in September or October, tion damage, soil compaction, and is supported by stored soil moisture improper fertilizer or chemical use. rather than spring or summer rains. Watering a pinyon pine should mimic natural rain or snow, and should be Pinyon pines in home landscapes done primarily from December to require minimal maintenance. They April if a winter is unusually dry. are growing in their native habitat, and therefore are adapted to the site. During periods of drought in winter Irrigation and fertilization are typically and early spring, trees should be given unnecessary except when trees have a deep watering monthly. Keep water been damaged by human activity or away from the root crown (Figure 1, weather. next page).

An exception to the “don’t irrigate Avoiding Stress Factors: Humans pinyon” rule is when trees have lost often impact trees with their daily roots due to excavation. Then it is activities. Trees that have been necessary to provide supplemental injured, above- or below-ground, are prime candidates for attack by insects irrigation to keep soil moist through and diseases. Root damage is a the growing season (May to Septem- ber). This should encourage new root common source of tree stress caused development to replace damaged by humans. roots. Be careful not to overwater; allow soil to drain between waterings. Root systems of pinyon are often Do not leave standing water in the damaged by overwatering. Because root zone. Pinyon pines need well- their native habitats are drier than drained soils. those of other pines, too much water can cause root problems and death. Construction often damages trees by Homeowners used to watering compacting soil, destroying roots, and landscape trees such as Austrian scraping bark. In order to protect (Pinus nigra) or Scotch (Pinus sylvestris) trees from construction hazards, pine regularly through the summer, protective zones should be estab- often mistakenly irrigate their pinyon lished around individual trees and similarly. Pinyon trees should never groups of trees. These zones should have irrigated landscapes planted be clearly delineated with brightly around them. colored flagging. 10

Since pinyon roots often extend out branches with a sharp knife. Do not from the trunk two to three times remove bark that is firmly attached. the tree’s height, and are located near Don’t use a sealant on wounds; leave the soil surface, it is difficult to avoid them exposed. damaging them. Therefore, it is important to consider these root systems when locating structures, Natural Target Pruning access lanes, and utility lines. Avoid 1. Find Target A — Just outside of paving over tree roots. the branch bark ridge. At a minimum, keep construction- 2. Find Target B — Swelling where related activity outside the dripline of branch meets collar. trees planned for retention (Figure 1). 3. Make cuts — Use the ‘three-cut’ method for two inch and larger limbs. Make a first cut on the underside of the branch 8 to 10 inches from where the branch connects to the trunk.

Cut a third to halfway through the limb. Make the second cut from 1 to 3 inches outside the first cut, starting on the top and cutting

through the branch. Make the final cut at line AB, just outside the Figure 1. Tree’s dripline and root branch collar. crown

Correcting Existing Problems: Homeowners often inherit tree problems upon purchase of a proper- ty. What can be done to reduce stress factors and encourage tree vigor in this case?

Prune off any broken branches or branch stubs. Pruning cuts should follow natural target pruning guide- lines (Figure 2). DO NOT: Remove any soil deeper than 6 inches • Cut behind the branch bark added during recent construction ridge over a tree’s root zone down to the • Leave stubs original soil grade. Aerate and mulch • Cut branch collar compacted soils and older fill. • Paint cuts

Loose bark should be removed from Figure 2. Natural target pruning the edges of wounds on the trunk or PINYON PINE Management Guidelines For Common Pests : 11

Trees that have sustained significant and all branches up as high as possible root damage may need to be sprayed on uninfested trees. March is the with an insecticide for one to two best time to spray. Contact Nevada seasons to protect them from bark Department of Agriculture for a list beetle attack. of pesticides registered for bark beetle on pine. There are no chemical sprays to save trees that are already infested with Another corrective action that can be beetles. However, spraying uninfested taken in an existing landscape is to trees with insecticides can protect remove lawn or other plantings them during times of stress or requiring water from the area between following injury. Spray the main trunk the trunk and the dripline of the tree.

PINYON PINE Management Guidelines For Common Pests : 13

PINYON FOREST MANAGEMENT GUIDELINES

he management guidelines for Trees infected with dwarf mistletoe pinyon contained here are very (see page 27), a parasitic plant, and Tgeneral. Specific recommendations those with numerous branch and need to be tailored to the individual stem cankers are also good choices site and take into consideration the for removal. Insect infested trees landowner’s objectives. should be evaluated for removal as well. Retain trees that have been Thinning: One of the primary good cone producers. Look for factors leading to poor tree health is immature and old cones in the too many trees spaced too closely. branches and accumulations of fallen Thinning, the selective removal of cones beneath the tree (Figure 3). individual trees to reduce tree density, is an important management Keep large trees with healthy, vigor- practice that improves tree health ous crowns (Figure 4, next page). If and vigor and decreases wildfire your property has both pinyon and potential as well. juniper, keep junipers too. A mixed stand will help deter the spread of Little research-based information insects and diseases. exists from which to develop guide- lines for thinning in pinyon stands. Try to achieve a spacing between There are, however, many general trees that is roughly equivalent to considerations that apply to all forest one and a half times the average tree types that should be considered height. Since all trees on a property when selecting trees for removal. will not be the same size, attempt to estimate the average height. By using Remove declining trees with dead and this spacing guideline, the number of dying branches and sparse foliage. trees retained per acre will be

Figure 3. Good cone production 14 greater with smaller trees, and also satisfactory methods of disposal. conversely, lower with larger trees. Avoid creating large amounts of slash in successive years, particularly during Timing of Cutting and Slash drought. Keep chip piles away from Management: Cutting operations live trees. They can attract bark should be carried out during late beetles to the area. fall and winter. This is the time when insects are inactive and less likely to Any infested material should be be attracted by freshly cut material. removed from the site or burned This will also allow time to clean up before the insects mature. To use the the slash and debris created by material for firewood, pile it in direct management activity prior to the sunlight and cover with at least four insects becoming active the following mil clear plastic. The smaller the pile, spring. the more effective this is – keep it just a few logs high. Be sure all edges Ideally, slash should be removed from of the plastic are buried and avoid the property. Alternatively, the wood tearing it. Leave the pile covered for can be left on site and cut into 12- three months during hot weather, and inch lengths. Keep wood exposed to longer during cooler times of the the drying sun. Split pieces larger year. Heat trapped under the plastic than 8 inches in diameter to speed will make the wood unsuitable for the drying. Chipping and burning are bark beetles.

Figure 4. Pinyon with a healthy crown and large cone crop PINYON PINE Management Guidelines For Common Pests : 15

COMMON PESTS

n Nevada, there are a number of insects and diseases of pinyon. The Ifollowing pests account for the majority of problems a homeowner is likely to encounter.

INSECTS

Pinyon Ips Beetle Ips confusus

Indicators: If you notice a pinyon changing color from green to yellow and finally to a reddish-brown (Figure 5), it may be infested with the pinyon Ips beetle (Figure 6).

By the time the color changes, the beetles Figure 5. Pinyon color change have usually left the tree, so carefully inspect green trees nearby for new attacks.

Look for boring dust (frass) collected in the bark crevices and at the base of the tree. Small globules of pitch (pitch tubes) and frass may be present at the entrance holes and in the bark crevices (Figure 7, next page). Egg tunnels or Figure 6. Adult Ips beetle (L. Livingston) galleries will be visible beneath the bark (Figure 8, next Nevada’s woodlands. The adult page). beetles are dark brown to black and approximately 0.2 inches long (Figure Description: Pinyon Ips beetles or 6). They first attack trees in the engraver beetles are native to spring as they emerge from woody 16

Unlike most other bark beetles, Ips egg galleries are free of sawdust and are etched into the wood (hence the name “engraver” beetles).

The eggs hatch into small white larvae that feed on the inner bark, and move out at right angles from the egg gallery. After a few Figure 7. Pitch tubes with boring dust weeks, they complete their growth, form a material infested the previous fall. pupal chamber at the end of the They continue their attacks through- feeding gallery, transform into pupae, out the summer. and then become adults.

If the attack is successful, the male The adults bore out of the tree and beetles release a chemical attractant, fly to new trees to begin another a pheromone, drawing a mass attack generation. They produce three to of other male and female beetles. four generations per year with the first generation emerging in April or The males bore through the bark and May, depending on temperature. The build a nuptial chamber in which they first generation typically infests mate with multiple females. The freshly damaged material, such as female beetles then bore egg galleries downed trees and broken branches. away from the nuptial chamber, laying eggs singly along both sides (Figure 8). This material is still green and provides a ready food source for the first generation, whereas live trees are most vigorous in early spring and are resistant to attacks. Trees become more susceptible as drier summer months progress.

The beetles carry a wood-staining fungus into the attacked tree. Figure 8. Ips galleries (D. McComb) PINYON PINE Management Guidelines For Common Pests : 17

The combination of larval feeding in Red Turpentine Beetle the inner bark and the fungus may Dendroctonus valens combine to eventually kill the tree. Indicators: Red turpentine beetles Prevention and Management: typically attack stressed or dying Since beetle attacks on healthy trees trees, freshly cut logs, and stumps. are usually unsuccessful, keep trees Their attacks are rarely fatal, however, healthy and vigorous. Thin over- they indicate a weakened tree and can crowded stands according to the predispose it to attacks by other bark guidelines presented earlier and beetles. prune out mistletoe infestations. See “PINYON FOREST MANAGEMENT The most obvious signs of red GUIDELINES,” page 13. turpentine beetle attack are large (up to 2 inches wide) reddish globules of For chemical spraying guidelines, see pitch (pitch tubes) at the point of page 11. entry (Figure 9).

These are located on the lower part of the tree trunk and on the root crown. Very weak trees may not produce much pitch in response to the beetle attack, and pitch tubes may be missing. However, accumulations of reddish-brown boring dust will be present at the base of the tree and in bark crevices. Piles of coarse, granular pitch are often present with the boring dust.

Figure 9. Pitch tubes from red turpentine beetle (B. Oakes) 18

The beetles also introduce a blue tine beetle larvae is unique and stain fungus into the tree. The fungus produces large chambers in the inner grows in the live wood tissue staining bark, rather than the individual larval the wood blue. tunnels as most other beetles produce. Description: The adult beetle has a distinctive reddish-brown color and is After two or more months, the larvae 0.25 inch to 0.5 inch long, making it transform into pupae. They remain in the largest bark beetle (Figure 10). this stage for another week or so as they turn into adult beetles. The adults attack trees throughout the warm season and generally peak The beetles then bore out through by mid-summer. The female beetle the bark, leaving small round exit bores through the bark and is soon holes, and fly to other trees to begin joined by a male with whom she another generation. The beetles breeds. normally produce one generation per

The beetles then chew a 0.5-inch to year, but may produce more in 1-inch wide egg gallery between the warmer climates. They spend the bark and wood. The gallery normally winter under the bark in either the extends down from the entrance hole adult or larval stage. and is filled with frass. The female lays groups of eggs, up to 100, along the Prevention and Management: sides of the gallery. Stressed and weakened trees are most often successfully attacked by In one to three weeks the eggs hatch red turpentine beetles. Follow into white larvae with brown heads thinning and slash management and a brown area on the hind ends. guidelines presented earlier to The larvae then tunnel in groups away prevent beetle problems. For from the egg gallery. The group- insecticide spraying recommendations, feeding characteristic of red turpen- see page 11.

Figure 10. Adult red turpentine beetle (T. W. Davies) PINYON PINE Management Guidelines For Common Pests : 19

Twig Beetle Pityophthorus spp. Pityogenes spp.

Indicators: Trees infested by twig beetle will have branch tips that are brown and dead. Careful examination of the small branches will reveal small pitch tubes where the insects have entered the branch (Figure 11). Bark on Figure 11. Twig beetle pitch tubes infected twigs may appear sunken and wrinkled (Figure 12).

Description: Another bark beetle, the twig beetle, attacks twigs less than 0.5 inch in diameter and the terminal growth. During drought condi- tions, the beetles will move to larger branches and the trunks of smaller trees. Figure 12. Sunken wrinkled bark resulting from twig beetle mining These beetles are approximately 0.1 inch in length. An infestation of twig Eggs are laid in the twigs. Then larvae beetles will usually not kill a tree, but tunnel into the food transporting will predispose it to other insect systems and inner bark, killing the attacks or disease. twig.

Twig beetles attack pinyon and other pine species. Natural outbreaks A gallery down the middle of the twig fluctuate year to year, but increases in is made for overwintering. Exit holes populations may be encouraged by are similar to the other bark beetles, drought and mild winters. There are but occur at the base of twigs rather two generations or more per year. than on the trunk or branches. 20

Prevention and Management: and thin. Trees with long-lasting Remove and destroy the dead twigs infestations will have a few short and branches. Winter is a good time needles clustered at branch tips. to prune out the infested material, because the adult beetles will also be Description: Adult scales look like removed. Cut the twigs back to small, black bean-shaped objects green growth. (Figure 13). Wingless females emerge in April after overwintering in The same chemical sprays that deter immobile waxy shells on the needles. pinyon lps beetle will also work against twig beetles. Chemicals will They then mate with winged males, not kill insects already in trees, but which are seen in large numbers flying may prevent successful attacks on around scale-infested trees. uninfested trees. After mating, females crawl to several

Pinyon Needle Scale sites on the tree, such as bark Matsucoccus acalyptus crevices, branch crotches, undersides of branches, and the root collar. Indicators: This is a sap-sucking There they lay clusters of oval yellow insect that feeds on previous years’ eggs held loosely together with thin needles. It weakens trees by killing sheaths of yellow cottony webbing needles. Small trees may be killed by that look like cotton candy (Figure 14, repeated feeding, and large trees next page). weakened to the point that they succumb to bark beetle attacks. In about four weeks, red eyespots become visible on the eggs. Seven to Foliage of infested trees turns yellow 10 days later, tiny yellow crawlers (chlorotic), then brown. Needle emerge. The crawlers move to the length is reduced and needles drop ends of branches, settling on year-old prematurely. Foliage of trees dam- needles. They insert their sucking aged for several years is chlorotic mouthparts and become immobile, covering their bodies with wax and turning black. This all happens in about one day following emergence. Feeding continues through the summer.

Figure 13. Pinyon needle scale PINYON PINE Management Guidelines For Common Pests : 21

Eventually, the scales grow too large Rake up litter and egg masses from for their initial waxy shell, which the area under the tree. Place the ruptures. A second developmental litter in plastic bags and dispose of it stage occurs on the needles as the immediately. In addition, a band of a scale develops a new waxy shell. The sticky trapping substance available immature males emerge from this from nurseries can be applied at the second stage in October or Novem- base of the washed tree trunk to ber. They have legs and crawl to the prevent crawlers on the ground from ground, where they spin loose webs gaining access to the tree crown. under stones, twigs, or in plant litter. Females spend the winter immobile Washing will be effective only when on needles. The life cycle is complet- the insects are in the egg stage, ed in one year. before crawlers emerge and disperse. This usually takes place in the Prevention and Management: beginning to middle of May or earlier Thoroughly wash the yellow cottony in southern areas. Drenching trunk egg masses from branch crotches, sprays are specifically registered for undersides of branches, and trunk of use on this insect. These should be the tree with a garden hose and spray applied against the adult stages in nozzle. early spring before egg laying. Sprays used against other scale insects should also be effective. Check with the Nevada Department of Agriculture for registered insecticides.

Figure 14. Pinyon scale egg masses 22

Figure 15. Pitch masses

trees are susceptible to attacks by other insects. The large amounts of pitch produced also increase the tree’s flammability.

Description: The borers live in the tree Pitch Mass Borer for one to two years and emerge as Dioryctria sp. adult moths. The adult lays eggs in bark crevices or near wounds Indicators: The larvae of this small throughout the summer months. The gray moth feed on the inner bark of eggs hatch into larvae that bore into pinyon and other pines. In their the branch or trunk. feeding, they excavate under the bark, causing wounds 2 inches to 4 inches Prevention and Management: in diameter. The tree produces large Maintain tree vigor. See “KEEPING masses of pinkish-white pitch in TREES HEALTHY,” page 9. Avoid response to the feeding (Figures 15 pruning or inflicting other injuries to and 16). The injuries caused by these the branches and trunk during attacks weaken the host tree and kill summer when the adult borers are individual branches. Heavily impacted active. Individual larvae can be controlled by removing the pitch mass and removing the larvae from under the bark with a knife or other sharp tool. Spraying trunks thoroughly with insecticide can reduce new attacks. Check with the Nevada Department of Agriculture for registered insecticides.

Figure 16. Pitch masses PINYON PINE Management Guidelines For Common Pests : 23

Pinyon Tip Moth They often will destroy the bud and Dioryctria albovitella move to another developing shoot or developing cone to continue feeding. Indicators: Larvae of this small, They pupate in the shoots or cones grayish moth feed in the branch tips and emerge in midsummer to begin of pinyon, killing new shoots and the cycle again. giving the tree a scorched appearance (Figure 17). Although the damage can be conspicuous, these larvae have Prevention and Management: As little effect on overall tree health. stated above, the damage caused by However, they can slow growth and this insect is superficial. However, it deform trees. can be controlled with insecticides.

Description: Adult moths lay eggs Spraying with insecticide in May, prior in midsummer. The eggs hatch soon to the larvae entering new buds, after, but do no damage in this early should be effective. larval stage.

The new larvae form a silken cocoon Spraying later in summer, when larvae on the bark and spend winter in this are moving to new food sources, stage. They emerge from the cocoon should also work. Check with the in late spring or early summer and Nevada Department of Agriculture begin feeding on unopened buds. for registered insecticides.

Figure 17. Tip moth damage 24

Pinyon Sawfly in late October and early November. Neodiprion edulicolus The eggs hatch in early April and groups of new larvae move to the tips Indicators: Sawfly larvae feed in of adjacent needles to feed (Figure colonies on the foliage of pinyon. 18). In June, the larvae drop to the Young larvae feed on the current ground and form cocoons beneath year’s needles, taking small bites that the litter layer (duff) or soil. The skeletonize the needle. Older larvae larvae pupate in the fall and emerge consume entire needles. as adult sawflies in October or November.

These sawflies typically go undetected because they occur in small numbers, Prevention and Management: causing little damage. However, they On individual trees, sawfly larvae can have become epidemic in the past, be blasted out of the tree with a causing widespread defoliation and garden hose. Most broad-spectrum mortality of smaller trees. insecticides kill exposed larvae. Insecticidal soaps and narrow-range Description: The adult sawflies, oils will also kill larvae and are less wasp-like insects, lay eggs in needles toxic to other non-target organisms.

Figure 18. Sawfly larvae group feeding (G. Durham) PINYON PINE Management Guidelines For Common Pests : 25

DISEASES

Black Stain Root Disease Root feeding beetles and weevils may Leptographium wageneri var. act as vectors, or carrying agents of wageneri the disease, spreading the disease organism as they feed and breed in Indicators: The black stain fungus recently dead or dying trees. As the causes a root disease that clogs beetles emerge, they are contaminat- water-conducting tissues of the roots, ed with spores and then move on and root collars, and lower stems of contaminate new host trees. Root pinyon, and blocks the movement of contact with adjacent trees is likely water to the needles. The fungus the most important means of spread. creates an arcing pattern on roots (Figure 19). Black stain kills young The fungus may also inhibit the flow trees within a year or two of infec- of pitch, reducing the tree’s protective tion. Older trees decline more mechanism that would normally allow slowly, but become susceptible to it to push out bark beetles. bark beetle infestation.

Description: Infected trees show Although pinyon can be a host for symptoms of gradual decline, with a black stain root disease, disease reduction in terminal growth and occurrence is not widespread. It is yellowing older needles. With the more appropriately considered a progression of the disease, older disease associated with certain needles drop off prematurely and new locations, rather than intimately tied needles may be stunted and yellow. to pinyon. It is also found on ponde- This causes growth in advanced rosa and Jeffrey pines. In those stages to be compact, yellow, and species it is associated with site sparse, creating a tufted look. There disturbance and damage to tree roots. may even be a “distress” cone crop, This association with disturbance has an abundant crop of cones. not been demonstrated with pinyons.

Figure 19. Infected root, note arcing pattern of Black Stain fungus (USDA Forest Service) 26

Prevention and Management: Pine needles are infected in late There is no cure for diseased trees. summer to early fall with no evident By reducing damage during construc- symptoms. The disease organism tion, site disturbances, and tree overwinters in the needles. By spring, injuries, further spread of the disease needles show yellow spots, with an may be reduced. Avoid soil compac- eventual rusty colored oozing tion. Do not cover root crowns with (exudation) occurring (Figure 20). soil or partially bury trees. Avoid changing drainage. For small, isolated As this disappears toward the end of infections, stump removal may summer, tiny scars or bands on green eliminate further infections. or partly yellowed needles occur. The fungal spores are then dispersed by Pinyon Needle Rust the wind, infecting the alternate hosts, Coleosporium jonesii currants and gooseberries (Ribes sp.). The organism repeats its growth and Indicators: Pinyon needle rust can dispersal cycle and reinfects pines. destroy enough foliage to disfigure or slow the growth of young pinyon Prevention and Management: To pines, but rarely causes significant help prevent needle rusts, do not damage that threatens tree health. plant the alternate hosts currants or gooseberries in the area. Prune Description: The cycle for rusts, infected tree branches and dispose of whether on leaf or stem, requires one them by burning or removing them year and two host plants. from the site.

Figure 20. Heavy needle rust infection (P. Murphy) PINYON PINE Management Guidelines For Common Pests : 27

Pinyon Blister Rust Pinyon Dwarf Mistletoe Cronartium occidentale Arceuthobium divaricatum

Indicators: Another rust disease, Indicators: The first visible sign of pinyon blister rust causes branch and pinyon dwarf mistletoe infection is a trunk swellings. It also needs cur- spindle-shaped swelling on a young rants or gooseberries to complete its branch. Two to three years following life cycle. infection, the plant produces yellow to light-green, leafless shoots up to 8 Description: Blister rusts deform inches long (Figure 22, next page). and kill trees or individual branches. Spores are released at night and spread by wind. They land on and “Witches brooms”, deformed loosely infect pine needles, shoots, and cones. arranged masses of twigs and foliage, The disease then spreads into the are another symptom of the disease branches and trunks, causing galls, that is easily visible in the crowns of cankers, and dieback (Figure 21). The infected trees (Figure 23, next page). activity of pinyon blister rust is associated with available moisture. Over time, the foliage of infected Infections are more likely to be trees becomes thin, short, and evident in wet years. yellowish, and the tree begins to die.

Prevention and Management: To Description: Dwarf mistletoe is a help prevent blister rusts, do not parasitic plant that causes widespread plant the alternate hosts currants or damage to pinyon. The plant spreads gooseberries in the area. Cut off primarily by seed. The berry-like infected tree branches and dispose of fruits ripen in the late summer or fall them by burning or removing them and burst, shooting their sticky seeds from the site. to other branches or trees.

Figure 21. Pinyon blister rust with typical bark blisters and rodent feeding (G. Durham) 28

years with mistletoe infections. The disease slowly weakens trees, making them more susceptible to other pests like bark beetles.

The length of time it takes for mistletoe to kill a tree depends on the age of the tree, how vigorous the tree is, and how heavily infected with mistletoe the tree is.

Prevention and Management: The Figure 22. best treatment option for mistletoe Pinyon dwarf mistletoe with swollen depends on the degree of infection, branch (F. Hawksworth & D. Wiens) the age and location of the tree, and concerns of property owner.

Seeds can travel horizontal distances Trees with severe infections, dwarf equal to their height in the tree. The mistletoe rating equal to 5 or 6 seeds adhere to needles, twigs, (Figure 24, next page), and those with branches, and trunks. They germinate only a few live branches should be the following spring. Infection of the removed. Trees with high, unreach- host occurs when the root-like able infections should also be re- structure from germinated seed moved to keep them from raining successfully penetrates the bark. seeds on uninfected trees below. Removal of heavily infected trees also The root-like system becomes eliminates the hazard that diseased embedded in the wood and provides trees can become around the home. the mistletoe with water and nutri- tion from the host tree. The mistle- toe plant continues to grow and spread in the host. Shoots of mistle- toe form within two to four years, and fruits are produced in another one to two years.

Dwarf mistletoe weakens trees by robbing them of food and water changing the balance of plant hor- mones that control growth. Infected trees grow more slowly, have de- formed branches, and produce less seed. The parasite can also kill trees.

Seedlings and saplings can be killed before they grow into large trees, Figure 23. Common dwarf mistletoe while larger trees can live for many symptoms PINYON PINE Management Guidelines For Common Pests : 29

All trees, particularly older ones, Mistletoe infections on branches should be examined to determine if within 6 inches of the tree trunk will decay, disease, or any other defect has likely have spread into the main tree created hazardous conditions. If the stem. If the main stem is less than 5 trees are isolated from uninfected inches in diameter where the infected pinyons (minimum separation of 30 branch attaches, the entire tree feet) they may be retained for their should be removed. Otherwise, aesthetic benefits. remove the infected branch and periodically scrape shoots off the Pruning infected branches can benefit trunk should they appear. trees with less severe infections.

Removing witches brooms can Examine pruned trees every two or improve the tree’s health and length- three years. Prune out any additional en its life. If more than 50 percent of infections and knock off new mistle- the tree’s crown needs to be re- toe shoots to slow its growth and moved to eliminate the infections, it is seed spread. best to remove the entire tree. An environmentally safe, growth- Remove infected branches where regulating chemical, ethephon, has they join the trunk or at branch been used to control the spread of junctions. Remove the entire branch dwarf mistletoes. rather than just the infected section, as not all infections will be visible. It causes the shoots to dehydrate and fall off. This treatment will not kill the Cut all visibly infected branches and two layers of branches above and parasite, but will slow its spread by below all infections. Forty percent of seeds. the total tree height should contain Thoroughly cover all shoots with the live branches following pruning. spray (until wet) to obtain good results. The chemical should be applied by mid-August before seed dispersal. Reapplication is needed as new shoots grow back to maturity and again produce seed.

Figure 24. Dwarf mistletoe rating system

PINYON PINE Management Guidelines For Common Pests : 31

CONCLUSION

inyon pines are important susceptible to attacks from insects Ptrees in the Great Basin. In the that can kill them and then spread to hom e landscape, they provide ecologi- infest trees in surrounding areas. cal, aesthetic, and financial value to the Dying or dead trees and dense stands property. The trees are assets when of trees around a home create a high they are healthy and growing vigor- fire hazard. ously. If properly cared for, they will be long-lived, providing beauty, wildlife By following the guidelines and habitat, and watershed protection. If recommendations in this publication, not cared for, the trees can become a landowners can ensure the pinyons on liability. Trees damaged by careless their property are an asset, rather than activity can become structurally a liability. They will provide years of unsound from decay fungi entering benefit to the property and its users. wounds. Wounded trees are

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GLOSSARY

Aerate – To physically “open” up a Dwarf mistletoe rating system – soil to allow air to penetrate, typically A simple method for evaluating the done with a core pulling machine. severity of dwarf mistletoe infections in a single tree or a stand of trees.

Canker – A lesion on a stem; a plant disease causing tissue dieback on Exudation – Liquid discharged from bark. diseased or damaged plant tissue.

Canopy – The leafy portion of a tree Fill – Soil added over existing native or stand of trees. soil.

Chlorotic – The yellowing of green Frass – Sawdust like material portions of a plant, particularly the produced by boring beetles, consist- leaves or needles. ing of ground-up wood and feces.

Crown – The foliage bearing branch- es of a tree. Gall – A growth or swelling that results from attack by bacteria, fungi, or other organisms.

Dripline – The ground area under the branches of a tree from the outermost reaching branches to the Galleries – Tunnels produced under trunk. the bark as boring beetles move through the tree to lay eggs, feed, mate, or exit.

Duff – The partially decomposed organic matter (litter of leaves, flowers, and fruits) found beneath Instar – The stage of an insect plants, as on a forest floor. between successive molts.

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Larva / larvae – Immature stage of Slash – Cut tree tops and branch an insect between egg and pupa; often wood resulting from tree or forest caterpillar- or worm-like in management activity. appearance.

Soil compaction – The reduction in Mulch – Any loose organic or air and water holding capacity (pore inorganic material placed over the space) of soil resulting from the effect soil. of traffic or weight on the soil

surface.

Pheromone – Attractant chemical produced by beetles. Spore – Of fungi, a one- to many- celled reproductive unit that becomes detached from the parent and that Pitch – Sap. can germinate to give rise to a new individual.

Pitch tubes – Globules of congealed sap that exude from branches and twigs. Terminal – The growth at the end of a stem or trunk.

Pupa / pupae – Resting stage of an insect between larva and adult. Thin – Selective removal of trees to the recommended distance to reduce competition for nutrients and water.

Root crown – The area of transition from stem tissue to root tissue located at the base of a tree. Vector – Carrying agent for a

disease organism.

Skeletonize – The lacy effect produced when insects chew up most of the green tissue on a leaf or Witches broom – Loosely arranged needle. masses of twigs and foliage.

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REFERENCES

Burns, R.M. and B.H. Honkala. 1990. Hessburg, P.F., D.J. Goheen, and R.V. Silvics of North America, volume 1, Bega. 1995. Black stain root disease conifers. USDA Forest Service of conifers. USDA Forest Service Agriculture Handbook 654. Forest Insect and Disease Leaflet 145. Washington, D.C. Washington, D.C.

Cranshaw, W. 1989. Biology and McCambridge, W.F. 1974. Pinyon management of pinyon pine insect needle scale. USDA Forest Service pests. Colorado Green, Summer, Forest Pest Leaflet 148. 1989. Washington, D.C.

Flake, H.W. Jr. and D.T. Jennings. 1974. McGregor, M.D. and O. Sandin. 1969. A cultural control method for pinyon Pinyon sawfly, Neodiprion edulicolus needle scale. USDA Forest Service Ross. USDA Forest Service Forest Research Note RM-270. Fort Collins. Pest Leaflet 117.

Francis, C., W.R. Jacobi, and W.S. Sinclair, W., H.H. Lyon, and W. Johnson. Cranshaw. 1999. Pinyon pine 1987. Diseases of trees and shrubs. diseases and insects. Colorado State Comstock Publishing Associates. University Cooperative Extension New York. Fact Sheet Number 2.948. Westcott, C. 1971. Plant disease Furniss, R.L. and V.M. Carolin. 1977. handbook. Van Nostrand Reinhold Western forest insects. USDA Forest Company. New York. Service Miscellaneous Publication 1339.

Hepting, G.H. 1971. Diseases of forest and shade trees of the United States. USDA Forest Service Agriculture Handbook 386. Washington, D.C.

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PHOTO CREDITS

Davies, T.W. © California Academy of McComb, D. Image 1678055. Sciences. Photo No. E220. www.forestryimages.org.

Durham, G. Nevada Division Murphy, P. Nevada Division of of Forestry. Forestry.

Hawksworth, F.G. and D. Wiens. 1996. Oakes, B. Image 2254026. Dwarf mistletoes: biology, pathology, www.forestryimages.org. and systematics. USDA Forest Service Agriculture Handbook 709. USDA Forest Service. Missoula Figure 16.40, page 204. Archive. Image 2250056. www.forestryimages.org. Livingston, L. Image 2253082. www.forestryimages.org.

McCambridge, W.F. 1974. Pinyon needle scale. USDA Forest Service, Forest Pest Leaflet 148. Figure 4, page 3.