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University Micrdfilms International 300 N. Zeeb Road Ann Arbor, Ml 48106 8510544

Akers, Rodney Cliff

REPRODUCTIVE BIOLOGY OF THE BRONZE BIRCH BORER, AGRILUS ANXIUS GORY, IN OHIO (COLEOPTERA: BUPRESTIDAE)

The Ohio State University Ph.D. 1985

University Microfilms

International300 N. Zeeb Road, Ann Arbor, Ml 48106 REPRODUCTIVE BIOLOGY OF THE BRONZE BIRCH BORER,

AGRILUS ANXIUS GORY, IN OHIO

(COLEOPTERA: BUPRESTIDAE)

DISSERTATION

Presented in Partial Fulfillment of the Requirements for

the Degree Doctor of Philosophy in the Graduate

School of The Ohio State University

Rodney Cliff Akers, B.A., M.S.

*****

The Ohio State University

1985

Reading Committee: Approved By

Dr. David G. Nielsen

Dr. Harry D. Niemczyk

Dr. Benjamin R. Stinner Department of Entomology ACKNOWLEDGMENTS

I would like to express my gratitude to Professors D. G. Nielsen, H. D. Niemczyk, B. R. Stinner, C. A. Triplehorn, G. R. Stairs, and R. D. Mitchell. Drs. Triplehorn, Stairs, and Mitchell offered helpful suggestions at the initiation of this study. Drs. Niemczyk and Stinner critically re viewed my progress throughout this study. Their interest and concern are appreciated.

Dr. Nielsen served as my committee chairman and helped in the design and implementation of this study. His persis tence in helping me strive for excellence, professionally and personally, was invaluable to my growth and success during this study.

I wish to thank others who contributed to this work. D. Cox, C. Birk, L. Birk, L. Blockus, and M. Dunlap provided much assistance in data collection. Special thanks to Michael Dunlap for his friendship.

Finally, I would like to thank my wife, Anne Trice, for editing and typing this dissertation, but above all, for her encouragement, confidence, patience, and understanding throughout the last four years. VITA

Peer uary 21, 1d 53 norn - aecford, Indiana

LjI o U.S., biology, Lynci'.burr Cc lie g e , i-.ynciibr.rg, Virginia i :< 7 -iy7c Gracuato Kesearch civ Teaching /issirtant, ueyarl- raont of Lnto.noiogy, V i r g i n ia Polytechnic Institute and State university, uiacksourg, Virginia i i) ~hj .S . , entomology, Vir ini a Polytechnic Institute ant.; State University, alacks- burg, Virginia

1 D 7 o Extension agent, Virginia C o o p e r a t i v e l. >: t e r: a ion c. r - vice, uUck ing nan:, Virginia,

I I O J or an ui; te h e s e a re., . u a e l — ate, Department of Lnto;.cl og y , on io .Ig r icuitu :a i desearcr. an... Development Center, 1 ne ukio state University, coo; ter, unio

Ph.D., n n toir.c- log y, Tne on io State University, Colu...bus, on io

i i i TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS i i

VITA...... iii

LIST OF TABLES...... vi

LIST OF FIGURES...... ix

INTRODUCTION...... I

LITERATURE REVIEW...... 5

EXPERIMENTATION...... 20

I. Influence of Post-Felling Treatment of Birch Logs on Adult Emergence...... 20

Materials and Methods...... 20 Results and Discussion...... 21

II. Spatial Emergence Patterns from European White Birch...... 29

Materials and Methods...... 29 Results and Discussion...... 30

III. Predicting Adult Emergence by Heat Unit Accumulation...... 40

Materials and Methods...... 40 Results and Discussion...... 41

IV. Host and Host Quality Influences on Reproductive Biology...... 57

Materials and Methods...... 57 Results and Discussion...... 62

iv Page

V. Mating Behavior...... 82

Materials and Methods...... 82 Results and Discussion...... 85

DISCUSSION...... 93

SIGNIFICANT FINDINGS...... 101

APPENDICES...... 10 2

A. Leaf Collection and Extraction...... 102

B. Determination of Total Phenols by Folin-Denis Method...... 103

C. Determination of Hydrolysable Tannins by KIO4 Method...... 10 4

D. Determination of Condensed Tannins by HC1 in n-BuOH Method...... 10 5

E. Determination of Tanning Coefficient by Protein Precipitate Method...... 106

F. Determination of Total Proteins by Bradford Method...... 107

LIST OF REFERENCES...... 108

v LIST OF TABLES

TABLE PAGE

1 Analysis of variance of factors and interactions influencing A. anxius emergence success under laboratory conditions, 1981 to 1983...... 22

2 Influence of felling date on A. anxius emergence under laboratory conditions...... 24

3 Influence of bolt end treatment on A. anxius emergence under laboratory conditions...... 25

4 Influence of weeks of cold storage on A. anxius emergence under laboratory conditions.. 28

5 Comparison of A. anxius, parasite, wood pecker predation, and total holes from B. pendula vs height near Wooster, OH...... 32

6 Comparison of A. anxius. parasite, wood pecker predation, and total holes from B. pendula vs circumference near Wooster, OH 33

7 Comparison of A. anxius, parasite, wood pecker predation, and total holes from B. pendula vs bark thickness near Wooster, OH.... 34

8 Comparison of A. anxius, parasite, wood pecker predation, and total holes from B. pendula vs compass direction near Wooster, OH. 36

9 Comparison of coefficient of variation for 10% A. anxius emergence in Ohio. Eight base temperatures and 4 starting dates were used for calculations...... 47

10 Julian dates of actual 10% A. anxius emergence compared to predicted emergence based on °D and linear regression...... 53

v i TABLE PAGE

11 Julian dates of actual and predicted 10% emergence of A. anxius adults in Ohio localities and years not incorporated into predictive models...... 54

12 Julian dates of actual 10% A., anxius emergence compared to recommended spray date.. 56

13 Longevity and length of maturation feeding period of A. anxius on selected trees near Wooster, OH, during 1980 through 1983...... 63

14 Host influnces on A. anxius fecundity and egg incubation period near Wooster, OH, during 1980 through 1983...... 65

15 Foliage consumption per A. anxius adult on selected hosts near Wooster, OH, in 1983...... 68

16 B . pendula leaf treatment effects on A. anxius adult longevity in 1983 near Wooster, OH...... 71

17 B . pendula leaf treatment effects on A. anxius adult reproductive biology in 1984 near Wooster, OH...... 72

18 B . pendula leaf traits assayed on 3 sampling dates during 1984 . Values are X ± S.E...... 74

19 Influence of cage movement on A. anx ius reproductive biology in 1984...... 80

20 Percent of A. anxus beetles copulating at different ages under laboratory conditions near Wooster, OH...... 86

21 Duration of copulation and time prior to first copulation of naive A. anxius adults under laboratory conditions near Wooster, OH...... 88

22 Comparison of copulation duration and time prior to copulation between naive and 3-min- interrupted A. anxius adults under laboratory conditions near Wooster, OH...... 90

v i i TABLE PAGE

23 Influence of mating frequency on longevity, fecundity, and egg hatchability of beetles fed on 2 host species near Wooster, OH...... 92

24 Oviposition by A. anxius females fed attached B. pendula foliage during 1981 through 1984 in the OARDC birch study area neat Wooster, OH...... 94 LIST OF FIGURES

Figure Page

1 Model of A. anxius reproductive biology...... 3

2 Daily temperature and % A. anxius emergence in Columbus, Ohio, 1981 through 1983...... 42

3 Daily temperature and % A. anxius emergence in Wooster, Ohio, 1981 through 1983...... 44

4 Linear regression of cumulative percent emergence of A. anx ius vs °D, based on Columbus, OH emergence. °D were computed from 1 May at 8 ° C base temperature...... 48

5 Linear regression of cumulative percent emergence of A. anxius vs °D, based on Wooster, OH emergence. °D were computed from 1 April at 10° C base temperature...... 50

ix Introduction

The bronze birch borer, Agr ilus anx ius Gory (Coleop- tera: Buprestidae), was first described by Gory in 1841.

It achieved notoriety as a serious pest of ornamental plants in the late 1890's when it was found infesting white-barked birch trees (Jack 1896; Chittenden 1898; Chamberlin 1900).

Chittenden (1898) coined its common name, bronze birch borer, because of its olivaceous-bronze, iridescent exoskeleton.

Larval feeding causes damage by scaring cambium, restricting phloem translocation, and interfering with move ment of water, ultimately causing tree death. Consequently, most studies have examined the larval stage and its impact on the host (Balch and Prebble 1940; Anderson 1944; Barter

1957; Ball 1979; Loerch 1983) .

Research on adults and their interaction with host trees is limited. They feed on willow, Salix sp., poplar,

Populus sp., and birch, Betula sp. (Larsen 1901, Slingerland

1906, Britton 1923, Hutchings 1923, Balch and Prebble 1940,

Barter 1957, Carlson and Knight 1969), but the influence of

1 host and host quality on its reproductive biology is un known. This study was initiated to investigate bronze birch borer reproductive biology. A broad approach was undertaken because of the lack of information about this beetle's reproductive biology ( Fig. 1). Techniques were needed to manipulate beetles for experiments as well as to examine host influence on beetle reproductive biology. Therefore, this study was conducted with the following objectives:

1. To manipulate infested birch logs to obtain beetles at

times when they are not otherwise available.

2. To examine spatial distribution of beetle emergence in

order to understand host exploitation and maximize ef

ficiency in selecting infested birches for obtaining

beetles.

3. To characterize seasonal beetle emergence.

4. To determine host foliage effects on reproduction.

5. To examine mating behavior in an effort to learn how to

maximize reproduction. Figure 1. .Model of A. anxius reproductive biology.

3 BBB Reproductive Biology Model

Maturation Faading Maturation Faoding

M ating

Boftavtor

v in m t- cu. Q AudHonr r|_ | yi»m l~i^ 1 A u^ m TI

S tim u li S tim u li

t vtauaI

c m c m

-C-. 5

Literature Review

General Description of Life Stages

A. anxius is endemic to North America, occurring throughout the range of birch in Canada and the United

States (Barter and Brown 1949; Fisher 1928). The adult is a subcylindrical buprestid beetle. Females are slightly larger than males, 7.7 to 11.3 mm vs 6.5 to 9.8 mm, respec tively. The first and second abdominal segments of males are grooved on the ventral side, a characteristic that can be used to distinguish males from females (Chittenden 1898,

Slingerland 1906, Hutchings 1923, Knull 1925, Barter 1957).

The egg ranges from 1.25 to 1.50 mm long and 0.75 to

1 . 0 0 mm wide; oval but flattened on two sides; creamy-white at first, changing to a yellowish color (Hutchings 1923;

Barter 1957). The female covers her eggs with a semi transparent protectant that cements the eggs to bark. Each larva bores directly through the egg shell into the bark and subcortical tissues.

The larva is a typical flatheaded borer with a small head, flattened and wide thoracic segments, and seven flat tened, ribbon-like abdominal segments. Full grown larvae are 8 - 2 0 mm long with white caudal segments terminating in two sclerotized, toothed, forcep-like prongs subparallel to the meson (Peterson 1967, Barter 1957). Damage to birch

trees is caused by larvae tunneling in a zigzag pattern in

the phloem or sapwood. In Ohio, larvae have four instars, overwintering usually as full grown larvae in a pupal cell.

Pupation in Ohio occurs from late April to early May

(Neiswander 1966). The pupa is creamy-white at first, then assumes adult coloration. Adults chew characteristic D- shaped holes in the bark during emergence.

History of Research Conducted

A. anxius was first identified as a pest of ornamental birches by Chittenden (1898) in Buffalo, New York, who pre dicted it would destroy every variety of birch within the city. Slingerland (1906) associated symptoms of birch top dieback in central New York with this borer. He conducted life history studies and reported that it had one generation per year with full grown larvae overwintering in cells near the bark surface. Adults emerged from May 15 through June

1; eggs were laid approximately June 8. The whole tree was usually infested by the time symptoms appeared.

Bronze birch borer was recorded as a forest pest by

Swaine (1918) who found it associated with dying birch in

the Ottawa river watershed. In forest studies, Pierson

(1927) found the greatest amount of A. anxius damage in birch stands where trees were left in the open after cutting of marketable trees. A strategy of cutting all trees was suggested to avoid borer problems. Pelt and Bromley (1930,

1931) suggested fertilizing and watering as a strategy to reduce borer attack. They improved vigor of heavily infes ted trees using these horticultural practices.

Spaulding and MacAloney (1931) studied birch decline on cut-over land. They concluded that A. anxius was not the primary pest, but that the borer and the shoestring fungus,

Armillaria mellea (Vahl), contributed to tree decline. En vironmental conditions caused the trees to become more sus ceptible to attack.

In 1940, Balch and Prebble examined the relationship of bronze birch borer to dying birch in New Brunswick. They discovered similar damage in virgin and cut-over forests caused by Agrilus larvae but did not believe the borer was the primary cause of birch mortality. The presence of large stands of mature and overmature trees, damage to birch trees from exposure due to cutting of softwoods, dying of soft woods due to budworm attack, and repeated attacks by birch defoliators contributed most to birch dying in New Bruns wick. In Nova Scotia, Hawboldt and Skolko (1948) investi gated dieback of yellow birch, Betula lutea Michx. They, too, found insufficient evidence to implicate bronze birch as the cause for the unmistakable and sometimes advanced

Symptoms o'f dieback. Anderson (1944) investigated the at tack of bronze birch borer in a northern Minnesota aspen- birch forest. Host condition was altered experimentally either by topping, girdling, felling, or a combination of

the above. Anderson surmised that A. anxius adults were attracted to and attacked decadent quaking aspen and paper birch trees, with the most stressed trees being the most susceptible to attack. He suggested that other factors, besides borer attack, should be considered when evaluating birch mortality.

In a later study by Barter (1957), A. anxius was studied in greater detail. Barter provided information that filled the gaps of earlier studies on life history, habits, and host-pest relationships. Effects of location, tempera ture, time of emergence, and host condition helped explain differences observed in other studies. Barter reported that larvae could not survive in healthy trees. Instead, larval development depended upon the host being predisposed by un successful attack, defoliation by herbivores, adverse weather conditions, or old age. In 1969, Carlson and Knight analyzed four sympatric Agrilus species, including A. an xius. They examined taxonomic characters, larval habits and ecological relationships to hosts, behavior of adults in the field and laboratory, and evolutionary relationships. They reported that A. anxius infested trees under physiological stress and appeared to be attracted to hosts by odiferous products of biodegradation.

Ball (1979) studied interactions of A. anxius and Eu ropean white birch, Betula pendula Roth, in the urban en vironment. He investigated the presence of A. anxius larvae and galleries in birch in various stages of decline. Borers emerged from the upper bole and crown of all trees exhibit ing branch dieback.

The latest study of A. anxius was conducted by Loerch

(1983). Morphometric analysis of immatures, vertical dis tribution of eggs, larvae, and pupae along tree boles, and egg and larval predation were examined at a strip mine reforestation site of European white birch in Pennsylvania.

Loerch determined that A. anxius had four larval instars in

Pennsylvania with the width of the peristoma, an exposed sclerotized portion of the head capsule, as the best struc ture for discriminating instars. Eggs, larvae, and pupae were found to be distributed vertically at random on the tree bole, with overwintering larvae primarily in the south west aspect. Only 10 percent of A. anxius eggs were para sitized, but woodpecker predation reduced overwintering lar val populations by up to 60 percent. 10 Laboratory, Spatial, and Seasonal Emergence

Laboratory Emergence. Research on wood-boring insects

is hampered by limited availability of insects for ex perimentation. Several families of borers can be reared on artificial diets, including Cossidae (Solomon and Abrahamson

1976), Sessidae (Antonio et al. 1975; Nielsen et al. 1980),

Cerambycidae (Cannon 1979; Galford 1974; Wollerman et al.

1969), and Pyralidae (Fatzinger 1981). However, efficient rearing procedures have not been developed for Buprestidae.

Mourkis and Vasilaina-Alexopoulou (1975) reported rearing the peach buprestid, Capnodis tenebrionis L., on a semisyn thetic diet. The effects of continuous rearing on the biol ogy of this beetle were not examined, but the time required for one reproductive cycle was the same as on natural hosts outdoors.

Since borer adults can often be collected from infested wood if natural infestations are available (i.e., Anobiidae,

Williams and Mauldin 1974), research concerning wood borers has usually been restricted to the time of the natural emer gence and flight periods. Consequently, research with buprestid beetles has been conducted exclusively during a two to three week emergence period of naturally occurring populations. Protocols for manipulating infested wood for obtaining beetle emergence at other times of the year is 11

needed to permit more intensive research with the beetles during a given year.

The influence of post-felling treatment of infested

wood on the success of beetle emergence is not known. Dun

bar and Stephens (1974) indicated that cooler temperatures caused by increased moisture in oak slabs outdoors delayed emergence of adult twolined chestnut borer, Aqrilus bilinea-

tus (Weber). Chittenden (1898) found larvae of bronze birch borer in wood that retained moisture (i.e., wood lying on the forest floor), but not in dry wood. Carlson and Knight

(1969) noted that emergence of Aqr ilus qranulatus liragus

Barter and Brown, was reduced by desiccation of bark layers and wood prior to the beginning of pupal eclosion.

Spatial Emergence Patterns. Information about spatial emergence is needed to optimize procedures for collecting infested wood for rearing insects in the laboratory. Host factors influencing distribution of emergence holes by subcortical feeders in woody plants have been examined exten sively in some beetle families, including the Scolytidae

(Berryman 1968; Ferrell 1978; Hodges and Pichard 1971;

Schenk et al. 1977; Shepherd 1965), but not for the Bupres tidae. Instead, investigations of host-emergence relation ships in the Buprestidae have emphasized host specificity and quality (Anderson 1944, Balch and Prebble 1940, Ball and 11 needed to permit more intensive research with the beetles during a given year.

The influence of post-felling treatment of infested wood on the success of beetle emergence is not known. Dun bar and Stephens (1974) indicated that cooler temperatures caused by increased moisture in oak slabs outdoors delayed emergence of adult twolined chestnut borer, Aqrilus bilineatus (Weber). Chittenden (1898) found larvae of bronze birch borer in wood that retained moisture (i.e., wood lying on the forest floor), but not in dry wood. Carlson and Knight

(1969) noted that emergence of Aqrilus qranulatus liragus

Barter and Brown, was reduced by desiccation of bark layers and wood prior to the beginning of pupal eclosion.

(Berryman 1968; Ferrell 1978; Hodges and Pichard 1971;

Schenk et al. 1977; Shepherd 1965), but not for the Bupres-- tidae. Instead, investigations of host-emergence relation ships in the Buprestidae have emphasized host specificity and quality (Anderson 1944, Balch and Prebble 1940, Ball and 12

Simmons 1980, Barter 1957, Carlson and Knight 1969, Chapman

1915, Hespenheide 1969, 1976). Developing protocols for choosing wood that contains a large number of overwintering larvae will increase chances of obtaining a workable beetle population from a minimum amount of wood.

Seasonal Emergence of A. anxius. Bronze birch borer has been associated with birch dieback since first cited as a pest of Betula. Attacked trees are thought to be pre viously stressed, since larvae have been reported to survive poorly in so-called healthy trees (Barter 1957, Hawboldt and

Skolko 1948, Spaulding and MacAloney 1931). Trees colonized by larvae usually die unless control measures are implemented.

Predicting seasonal emergence is important in determin ing when beetles will be available outdoors. Carlson and

Knight (1969) remarked ". . . that in most parts of their ranges, peak emergence for (Aqrilus) anxius, 3 . liraqus, and horni occurs during June, but even within a given region there can be significant year-to-year variations in the emergence pattern." Apparently, variations in emergence periods relate to temperature.

Pheromone traps are useful in monitoring seasonal flight activity of some insect borers, such as clearwing moths (Lepidoptera: Sessidae) (Nielsen et al. 1975, Barry et al. 1978, Nielsen et al. 1978, Nielsen and Purrington

1978, 1980), but long range pheromonal communication has not been demonstrated for Aqr ilus beetles. Predicting emergence by correlation with monthly temperatures worked well with the rose stem girdler, Aqr ilus aur ichalceus Redtenbacher

(Davis and Raghuvir 1964) and the red-necked cane borer,

Aqrilus ruficollis (Fabricius) (Walton 1951). Potter and

Timmons (1983) developed a method for predicting seasonal flight activity for another landscape pest, the lilac borer,

Podosesia syringae (Harris), by accumulating degree-days from a prescribed threshold temperature while capturing male moths in pheromone traps. Since Aqrilus beetle emergence is apparently temperature dependent and a heat unit summation model has proven effective with another borer in the urban landscape, predicting A. anxius emergence by accumulating degree-days may be feasible.

Hosts and Host Quality Influences

on Reproductive Biology

Although A. anx ius was recognized as a serious pest of ornamental birches in the late 1800's, research has concen trated on the larval stages of A. anxius because of its ob vious impact on the host (Balch and Prebble 1940, Anderson

1944, Barter 1957, Ball 1979, Loerch 1983). The limited research that has been conducted with adults is dominated by 14

host foliage preference tests. Britton (1923) observed

adults feeding naturally on willow, Salix sp., poplar, Popu-

lus sp., and birch, Betula sp. Field observations by Hutch

ings (1923) indicated beetle preference for poplar and wil

low foliage over birch. Carlson and Knight (1969) main

tained adults in the laboratory on apple pieces, but con cluded that tree foliage was the probable food source. In

laboratory preference tests, beetles consumed more poplar and willow than birch foliage and preferred quaking aspen,

Populus tremuloides Michx. (Barter 1957; Nash et al. 1951).

The influence of host foliage on the reproductive biology of

A. anxius is unknown.

Recent studies have demonstrated that host species and quality both influence herbivore success. Many theories have been used to explain insect population cycles. One explanation receiving research attention is plant quality and natural host defenses. Feeny (1975, 1976) and Rhoades and Cates (1976) described plant defenses as either

"qualitative" or "quantitative." Early successional plants are short-lived and unpredictable for insect herbivores.

These plants have evolved toxins or "qualitative" defenses'.

Late successional plants are long-lived and predictable.

These have evolved digestability reducers or "quantitative" defenses. 15

Plant defenses are not easily characterized. Plants

subjected to attack by herbivores may respond quickly or

with long term defenses. Short term responses influence

insects currently attacking the plant, whereas long term

responses influence succeeding herbivore generations.

Rhoades (1983) indicated that leaf quality in Sitka

willow, Salix sitchensis Sanson, was altered in trees fed

upon by western tent caterpillars, Malacosoma californicum

pluviale (Packard). Nearby trees that had not experienced

current herbivory also responded in a defensive mode.

Rhoades suggested that this message may have been sent

through airborne pheromonal substances.

Baldwin and Schultz (1983) discovered that potted pop

lar, Populus x euroamericana, ramets had increased con

centrations and rates of synthesis of phenolic compounds within 52 hours of having 7% of their leaf area removed by

tearing. The same response occurred in undamaged plants

sharing the same enclosure. Since phenolic compounds are detrimental to herbivores, this experiment suggested that

the feeding and growth of phytophagous insects could be in

fluenced by airborne cues originating in nearby damaged tissues. Schultz and Baldwin (1982) also reported long-lasting

defensive response in red oak, Quercus rubra L., to herbivo

ry. Defoliation of red oaks by gypsy moth, Lymantria dispar

L., larvae during the previous year and current year (same

trees) resulted in leaves with higher levels of total phe

nols, hydrolyzable and condensed tannins, lower water con

tent, and increased toughness than did leaves from undamaged

trees. Wallner and Walton (1979) found that gypsy moth lar vae reared in the field on artificially defoliated gray

birch, Betula populifolia Mash, and black oak, Quercus velutina Lam., had reduced survival compared to larvae

reared on undefoliated trees. The effects occurred not only

in the first year of defoliation, but were intensified the

second year. Defoliation altered the nutritional value of

the foliage and influenced the biology of gypsy moth larvae.

Long-lasting and inducible defensive responses have been investigated in the genus Betula. Werner (1979) found

that larval development rate and survival of the spear- marked black moth, Rheumaptera hastata (L.), decreased when

larvae were fed foliage from paper birch, Betula papyrifera

Marsh, that had been defoliated for two and three years.

Considerable evidence for an inducible defense has been

found by injuring foliage of mountain birch, Betula pubescens spp. tortuosa Ledeb., in Finland. Haukioja and Niemela

(1976, 1977) reported retardion of growth of larvae of a 17 geometrid moth, Epirrita autumnata (Bkh.), when they were fed previously grazed leaves or on nearby leaves on the same plant. In later studies, changes in leaf phenolics were suggested as the probable cause for reduced larval growth

(Haukioja and Niemela 1979, and Niemela et al. 1979).

Leaves of Betula pubescens ssp. pubescens exhibited an anti-herbivore defense response. Palatability of damaged and adjacent undamaged leaves was reduced when assayed with a snail, Helix aspersa Muller (Edwards and Wratten 1982), a general herbivore. In the same birch species, Wratten et al. (1984) used the polyphagous lepidoptera, Spodoptera littorals (Pack.) and rusty tussock moth, Orgyia antiqua

(L.), and reported reduced, foliage palatability in damaged and adjacent undamaged leaves from 6 hrs to 5 months follow ing initial damage. Initially, soluble phenol levels in creased with wounding and correlated with palatability, but measured levels of phenols in later months did not correlate with bioassays. They suggested that these soluble phenols may be precursors of other insoluble phenolic compounds and it is these compounds which change leaf palatability.

Mating Behavior

Larvae of several insect families tunnel extensively in phloem, destroy cambium, and bore into xylem tissues. Adult mating behavior of many of these subcortical feeders is well 18

known. Members of the Scolytidae are attracted to volatiles produced by conspecific beetles and attacked hosts. This

response has been documented in Ips, Dendroctonus, and

Leperisinus species (Vite and Gara 1961, 1962, Rudinsky

1963, 1966, Renwick and Vite 1969, Silverstein, et al. 1966,

Werner 1972a, 1972b, Birch 1978, Rudinsky and Vernoff 1979).

These host volatiles and/or pheromones influence mating be havior of bark beetles. Typically, pioneer beetles select a host tree and begin to release pheromones as they bore into subcortical tissues. These odors initiate mass attack by conspecifics. Either to reduce rivalry or to recognize the opposite sex, beetles stridulate as they meet. As beetle density increases, a threshold level of volatiles/pheromones is reached which causes arriving beetles to switch to other trees. In neighboring trees, the colonization cycle begins again (Birch 1978, Payne 1981).

Pheromones play a major role in mate location among lepidopterous borers. Sex pheromones are emitted by fe males; males detect and take flight toward females in their pheromonal plume. Upon arrival at calling sites, males lo cate females and copulation occurs (Farkas and Shorey, 1972,

Nielsen 1978, Nielsen et al. 1975, Barry et al. 1978, Niel sen et al. 1978, Nielsen and Purrington 1978, 1980, Barry and Nielsen 1984). 19

Little is known about the mating behavior of buprestids. Only one buprestid species, Xenorhipis brendeli Le

C., has been reported to use sex pheromones as previously described. Wellso (1966) found that male X* brendeli pos sess elaborate pectinate antennae and he assumed that these sensory organs were used to locate virgin females. Ap parently mate location by most buprestids is facilitated by host selection. Beetles of the genus Melanophila are at tracted to burned trees over distances of several kilometers

(Mathews and Mathews 1978, Evans and Kuster 1980). Informa tion about Agrilus spp. indicates that they, too, depend upon host selection to facilitate mate location (Carlson and

Knight 1969). Selection of mating and oviposition sites is governed by many of the same factors (Carlson and Knight

1969). Once on the host, mate recognition appears to occur through visual and tactile cues (Carlson and Knight 1969,

Gwynne and Rentz 1983). Although much is known about the mating behavior of some wood borers, there is need for be havioral research with buprestids to elucidate environmental and intraspecific cues that are used in mate location and selection. EXPERIMENTATION

I. Influence of Post-Felling Treatments of Birch Logs on

Emergence

Materials and Methods

Infested European white birch, Betula pendula Roth, in

northeastern Ohio were felled during fall (17-22 Sept.)?

winter (16-22 Dec.)» and spring (18-29 Mar.) seasons from

1980 to 1983. Wood from each felling date was initially

divided into 3 equal groups of similar-size bolts, and all

old A. anxius emergence holes were circled with a wax pen

cil. Each group received 1 of 3 end treatments; ends sealed

with hot parafin; 1 end standing in distilled water; no end

treatment. Each bolt from the 3 initial groups had equal

opportunity for inclusion in 1 of the temperature treat ments. Some bolts within each treatment were placed direct

ly into an emergence room (rm 1 @ 26°C, 45% RH; rm 2 @ 22°C,

80%RH) or in cold storage at 2-3°C. Bolts held in cold

storage for 6 or 8 weeks were kept in closed 190 liter plas

tic containers with 0.3% sodium hypochlorite solution in the

bottom. After cold treatment, bolts were placed in 1 of the emergence rooms until emergence was complete. New emergence

20 holes and surface area of all bolts were recorded after adult emergence from each group of bolts.

Date of felling, weeks in cold storage and bolt end treatments were analyzed with a 4-way ANOVA to determine which treatments expedited, delayed, or reduced emergence.

Means were separated using Tukey's test for significance.

Results and Discussion

There was no way to determine larval density in trees prior to felling. The only way to measure the influence of cutting date on beetle development and emergence was to record emergence and then count dead larvae within bolts.

This was done the first two years of the study.

Date of felling and bolt end treatment were the only factors that significantly affected the density of A. anxius adult emergence in the laboratory (Table 1). Emergence den sity differences between rooms, weeks of cold treatment, and all interactions between factors were insignificant for all test years, but were important in determining when emergence occurred.

Felling. Date of felling was highly significant in influencing beetle emergence from infested logs (Table 1;

P < 0.001). In 1980-1981 and 1981-1982 significantly more 22

Table 1. Analysis of variance of factors and interactions influencing A. anxius emergence under laboratory conditions, 1981 to 1983.

Source Mean squares/year of variation DF 1980-1981 1981-1932 1982-1983

Rearing rooms I bib . 2 E U J • ^ ^

1 - , . N , K * * ... ★ * ■* - — . * * * Felling date 2 1JiOuu • - Oo3’.U C * . / 1; » J

V.eeks

in cold storage 0 191. J X• ' ^ . 7t m

'/veeks* felling ■4 O i / • o c. J 0 ^ J • J

Bolt end treatment (BET) 2 d U U 2 . -i * S .j i * ‘l

BET* felling 10713 . d O • 7 «j S' “1 •

i n r. r » . *v B E T * weeks ‘t 8 0 0 >j . 7 X w/ • -F W -E •

B E T * weeks*

felling J 31 11 .0 1 LU • J 2 U J/ •

Error j j t i • j J ‘ j •

** ^ * F < 0 . U 0 1 O t u x 1- < 0 . 0 b 23 beetles, 5x and 2.8x, respectively, emerged from bolts fel

led in winter and spring than in fall. In 1982-1983, winter-felled bolts produced significantly more beetles, 43 adults/m2 bark surface, than either fall-felled (7 adults) or spring-felled (15 adults) bolts (Table 2). Although fall and spring fellings were not significantly different, spring felling produced 2x more beetles than fall felling in 1982.

In terms of overall beetle emergence per unit bark sur face, infested bolts cut in 1980-1981 produced approximately

11.7x and 5.6x more beetles than bolts cut in subsequent years 1981-82 and 1982-83, respectively. Birch bolts used for experimentation are chosen by subjective criteria, in cluding amount of crown dieback and presence of attached dead leaves. From past experience, birch trees exhibiting these signs usually are infested with borers. There is no way to predict the larval density in felled trees. There fore, the lack of significant differences in adult emergence density between fall and spring felling in 1982-1983 prob ably reflects variability of larval density between trees.

Bolt End Treatment. Bolt end treatment influenced density of beetle emergence (Table 3). Significantly fewer beetles emerged from bolts with 1 end in water than from those with waxed ends in 1980-1981 and from those with waxed 24

Table 2. Influence of felling date on A. anxius emergence under laboratory conditions.

Felling X Acult emerqence z■ £>.D./m^— ~ r, / O1/ date 1980-■1981 LS81-1982 1982-1983

Fall Cu.j 1 2 u . b a « b 21 O . li c.‘ 1 • -i J2 b • L) c:

Winter lbb.0 ± 'j 7 . :< . j £ u • b 2. _l jj, j j

Spr ing L

±.‘ We a:i s £ o j. l c a' e <_ uy ejrr.e let ter are not s io n ificar L.., i. l- I 0 L .•nt, xukey *s tost, y < 0.0b. 25

Table 3. Influence of bolt end treatment on A. anxius emer gence under laboratory conditions.

Bolt end X Adult emerqence + S.D./m2 1/ treatment 1980-1981 1981-1982 1982- 1983

None 127.1 + 112.3ab 11.4 ± 12.2a 24.2 ± 26.0a

Waxed 160.1 ± 132.2a 15.0 ± 10.5a 23.5 ± 28.6a

End in water 81.5 ± 58.4b 5.1 ± 5.6b 17.6 ± 25.5a

•i/ Means followed by same letter are not significantly dif ferent, Tukey's test, P < 0.05. 26

or unwaxed ends in 1981-1982. In 1982-1983, bolt end treat

ment did not influence adult emergence." -

Wood quality deteriorated rapidly in bolts with 1 end

in water in 1980-1981 and 1981-1982. Emergence densities

were statistically similar from bolts with waxed ends or

without waxed ends and not standing in water, but waxed

bolts usually had more emergence. Lack of moisture within a

bolt may not become a critical factor when bolts are placed directly in an emergence room, since beetles emerged within

2-4 weeks once bolts were subjected to emergence tempera

tures. However, if bolts are to be placed in cold storage

for more than a few weeks, waxing their ends may enhance beetle production.

No differences in 1982-1983 between end treatments may be because bolts with 1 end in water required more frequent watering than in pervious years. During the first 2 years, the prescribed water level was maintained by watering once per week, but the water level decreased more rapidly in

1982-1983, requiring watering every 3-4 days.

Temperature. Weeks of cold treatment did not in fluence density of beetle emergence from bolts (Table 4).

However, temperature was used to delay beetle emergence.

Winter- or spring-felled bolts placed directly in the rear ing room did not produce more beetles than bolts held 6 or 8 27 weeks in cold treatment (Table 4). Since beetles were over wintering and had already been exposed to cold outdoor tem peratures when winter and spring wood collections were made,

further cold treatment did not affect emergence success. In

fact, beetles will emerge in July and August from bolts held

in cold storage from March or May.

Regardless of felling date, beetles began emerging from

infested bolts ca. 2 weeks following placement at warm tem peratures. Beetle emergence density did not vary between emergence rooms (Table 1), but emergence began ca. 8 days sooner in the warmer and less humid room (260 c and 45% RH).

Conclusion

Bronze birch borer adults can be obtained from fall through spring by placing infested wood in an emergence room. Length of cold storage did not influence beetle emer gence. Emergence can be maximized by felling trees in winter through spring and, perhaps, by waxing bolt ends. 2d

Table 4. Influence of weeks of cold storage on A. anxius emergence under laboratory conditions.

Weeks ' o*/ of cold X Adult emerqence ± S . D . / m Z - incubation 1980--1981 1981-1982 1982-1983

0 123.3 ± 12o.l 11.2 ± 11.0 15.8 ± 17.6

6 125.6 ± 94.4 10.7 ± 10.4 20.2 ± 16.5

8 119.3 ± 109 .4 9.6 ± 10.7 2y .3 ± 38.6

1/ Means within each year were not significantly different, AMOVA, P < 0.05. 29

II. Spatial Emergence Patterns from European White Birch

Materials and Methods

Twenty recently killed European white birch, Betula

pendula Roth, with unbroken tops were selected from a com

mercial nursery near Shreve, Ohio, and a research nursery at

the Ohio Agricultural Research and Development Center,

Wooster. A wax pencil was used to delimit compass direc

tions on trunks before trees were cut. Trees were then fel

led to facilitate data collection. Tree trunks were cut

into 1 m bolts beginning at ground level. Bolt ends were

measured to the nearest mm and averaged to determine circum

ference. Bark thickness was derived as the average of 2

measurements per compass direction per bolt. All A. anxius,

Phasgonophora sulcata Westwood, a larval parasitoid of A.

anxius, and woodpecker predation holes were then counted to measure influence of aforementioned variables on emergence

hole density on tree trunks. In addition, emergence hole density in limbs and branches of the canopies were compared with that in the trunks. 30

Results and Discussion

Beetle and Total Holes vs Height, Circumference, and Bark Thickness

An average of 184 + 82 (SD) beetles and 290 + 162 (SD) total holes (beetle, parasitoid, and woodpecker) were re corded from trunks of trees 3.4 to 8 m tall. A. anxius emergence and total holes per m2 bark area were regressed on the variables height, circumference, and bark thickness of bolt. These relationships can best be described by the fol lowing equations:

Logio BBB/m2 bark area = 0.48 - 2.61 C + 1.69 logig BT

r2 = 49.9, P < 0.005

Lo9 l0 total holes/m2 bark area =

0.63 - 3.01 C + 1.80 logBT

r2 = 52.2, P < 0.005, where BBB/m2 bark area is the density of beetle emergence holes per unit area, total holes/m2 bark area is the density of all holes per unit area, C is average circumference (cm), and BT is average bark thickness (mm) of tree trunks. The variable height did not add significantly to the equation.

Although only ca. 50% of emergence holes and total holes can be explained by circumference and bark thickness variables, 31 the relationship is significant and warranted analyzing con tinuous variables height, circumference, and bark thickness as discrete variables.

One-way ANOVA (P < 0.05) for each variable, height, circumference, and bark thickness, indicated a significant difference in emergence density for beetles and total holes.

Means were separated by Duncan's (1955) new multiple range test (P = 0.05). Fewer beetles emerged at the 6 m height,

0.1 to 5.0 cm circumference, and 0.1 to 1.5 mm bark thick ness than from bolts 1 to 3 m above ground, 5.1 to 60.0 cm circumference, and with bark 1.51 to 3.0 mm thick (Tables 5-

7). These factors are interrelated, since circumference decreases and bark becomes thinner as tree height increases.

Although emergence and total holes were greatest in the lower trunk, emergence hole and total hole density was even ly distributed except for the upper tree crown. There was little emergence from bolts less than 5 cm in circumference.

This may be due to crown tissues becoming necrotic before larvae complete development. Small larvae are probably not pitched-out of susceptible trees because they feed in a zig zag pattern that tends to minimize exposure to high vascular pressures (Barter 1957). Ball and Simmons (1980) and Loerch

(1983) recorded more beetle emergence from the lowest sec tion of the trunk, but when emergence was adjusted for unit Table 5. Comparison of A. anxius, parasite, woodpecker predation, and total holes from B. pendula vs height near Wooster, OH.

X Parasite emergence fc X A. anxius woodpecker X Total emergence/m2 predation/m2 emergence/m2 Height No. of bark surface ± bark surface ± bark surface! (m) observations S.D. 1/ S.D. 1/ S.D. 1/

1 19 247.8 ± 180.3a 28.0 ± 33.4b 275.8 ± 193.3a

2 19 250.6 ± 158.4a 105.5 ± 80.4a 356.1 ± 178.3a

3 19 225.3 ± 182.0a 180.3 ± 154.3a 405.6 ± 293.2a

4 19 158.6 ± 153.0a 123.4 ± 143.4ab 282.0 ± 265.2ab

5 8 198.4 ± 245.4ab 234.0 ± 312.6ab 432.4 ± 497.Oab

6 4 53.8 ± 89.8b 153.4 ± 185.4ab 207.1 ± 267.5b

Data were transformed to log^o (X + 1) before analysis. Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Duncan's (1952 new multiple range test) .

to Table 6. Comparison of A. anxius, parasite, woodpecker predation, and total holes from B. pendula vs circumference near Wooster, OH.

X Parasite emergence & X A. anxius woodpecker X Total emergence/m2 predation/m2 eaergence/a2 Circumference No. of bark surface ± bark surface ± bark surface ± (cm) of bolt observations S.D. X/ S.D. 1/ S.D. 1/

0 . 1 to 5.0 8 33.3 ± 94.3c 5.6 + 15.7c 38.9 + 1 1 0 .0 c

5.1 to 1 0 . 0 18 189.8 ± 189.8ab 169.8 + 235.7ab 359.6 + 374.Oab

1 0 . 1 to 15.0 16 259.9 ± 160.9a 224.6 + 159.1a 484.5 + 257.0a

15.1 to 2 0 . 0 15 249.4 ± 156.3a 139.5 + 140.5a 388.9 + 255.6ab

2 0 . 1 to 25.0 14 258.3 ± 170.9a 1 0 2 . 8 + 1 0 2 .8 ab 361.1 + 180.2ab

25.1 to 35.0 16 237.2 ± 186.8ab 39.4 + 45.6b 276 .6 + 204.Sab

35.1 to 60.0 9 87.9 ± 47.7b 102.7 + 85.8ab 190.6 + 120.9b

Data were transformed to log^o (X + 1) before analysis. Means within a column fol lowed by the same letter are not significantly different at the P = 0.05 level (Dun can's [1955] new multiple range test).

U) CJ Table 7. Comparison of A. anxius, parasite, woodpecker predation, and total holes from B. pendula vs bark thickness near Wooster, OH.

X Parasite emergence & X A. anxius woodpecker X Total Bark emergence/m2 predation/m2 emergence/m2 thickness(mm) No. of bark surface + bark surface + bark surface ± of bolt observations S.D. 1/ S.D. 1/ S.D. 1/

0.1 to 1.5 37 174.4 + 185.8a 151.0 + 218.3a 325.4 + 359.3a

1.51 to 3.0 37 250.2 + 167.9b 123.9 + 95.7a 374.1 + 201.5b

3.1 to 7.4 22 185.2 + 146.0b 73.2 + 82.0a 258.3 + 269.Oab

Data were transformed to log^Q (x + 1) before analysis. Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Duncan's [1955] new multiple range test) . surface area, emergence hole density did not vary signifi cantly between sections of tree trunks. However, we found that the penultimate and ultimate bolts had significantly less emergence, both actual and per unit area, than the rest of the tree trunk.

Since 29.4% of the total holes on B. pendula trunks were from woodpecker predation (25.4%) and parasite emer gence (4.0%), we examined the sum of these holes (woodpecker and parasite) separately from total holes. One-way ANOVA (P

0.05) for variables height and circumference indicated a significant difference (Tables 5 and 6 ). Significantly fewer holes were found in the 1 m bolt nearest the ground than in bolts 2 to 3 m above ground. There was no signifi cant difference between 1 m and 4 to 6 m bolts, but parasite emergence and woodpecker predation was extremely variable from tree to tree. Bark thickness did not influence parasite activity or woodpecker predation (Table 7), but fewer holes were found in the thickest bark. Significantly more holes occurred on the south side of the tree than the north side (Table 8 ). As expected, there was a high cor relation (r = .87) between woodpecker predation and parasite emergence compared to total holes on each tree. Since 8 6 % of the combined woodpecker predation and parasite emergence holes is due to woodpecker predation, the low occurrence of these holes from the 1 m bolt nearest the ground indicates Table 8. Comparison of A. anxius, parasite, woodpecker predation, and total holes from B. pendula vs compass direction near Wooster, OH.

Compass X % ± S.D. X % ± S.D. X % ± S.D. direction of A. anxius of parasite emergence of total on bolt emergence!/ and woodpecker predation!/ emergence!/

SW 38.2 ± 10.1a 35.2 ± 18.9a 37.5 ± 9.8a

SE 27.4 ± 6.7b 31.3 ± 14.2a 28.1 ± 6.4b

NE 15.1 + 5.8c 16.4 + 7.9b 15.5 + 5.8c

NW 19.3 + 5.4c 17.1 + 7.8b 18.9 + 5.2c

1/ Data were transformed to log^o (X + 1) before analysis. Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Duncan's (1955| new multiple range test) .

0 4 o\ - 37 that other factors besides larval distribution influence woodpecker predation.

Emergence VS Cardinal Compass Direction

ANOVA indicated a significant difference in emergence holes and total holes associated with different compass di rections (Table 8 ). To adjust for different tree heights, we calculated % of A. anxius and total emergence from each tree before analysis. Significantly more emergence occurred from the SW quadrant than from other quadrants. Signifi cantly more beetles emerged from the SE quadrant than from the NE or NW. These results are not surprising, since A. anxius adults are photopositive, responding to environmental cues above a temperature threshold of 20°C (Barter, 1957,

Larsen 1901). The south side of a tree is the warmest and the SW quadrant usually receives more sunlight above this temperature threshold than other quadrants. Ovipositing beetles may respond to these stimuli by spending more time on the SW side of trees. Larvae may dwell in the sunny, warmer portions of the tree when completing development.

Loerch (1983) reported that overwintering A. anxius larvae and pupae were concentrated in the SW side of paper birch,

Betula papyrifera Marsh. ’ 38 Bole vs Branch Emergence

Beetle emergence and total holes were significantly less from branches, 61 ± 69 and 116 + 143 (X ± S.D.), respectively, than from tree trunks, 184 ± 82 and 280 ± 153

(X ± S.D.), respectively, according to Student's t-test (P^

0.01). When emergence holes were converted to number/m2 of bark area, similar results were obtained. There were sig nificantly fewer emergence holes and total holes in branches, 46 ± 37 and 83 ± 5 6 (X + S.D./m2 bark area), than in tree trunks, 232 ± 122 and 330 ± 156, according to Stu dent's t-test (P < 0.01). Ball and Simmons (1980) sampled

A. anxius larvae by removing 10 cm strips of bark from B. pendula trees, and also found significantly lower larval density in branches than in tree trunks.

Conclusion

A. anxius larvae utilize branches and tree trunks as food resources. Less emergence occurs from branches and the upper portion of the trunk, perhaps as a result of host colonization sequence. As larvae become established, they interfere with phloem translocation and may alter host quality above and below larval feeding sites. These alter ations probably influence larval survivorship. 39 A typical progression of dieback occurs in birch

* * basipedily starting with "flagging" in the upper canopy with little or no beetle emergence. Later the lower bole becomes heavily infested producing large numbers of beetles (Akers and Nielsen, unpublished). Mass emergence from a tree during the year of its death would seem to be adaptive.

Since beetles cannot colonize dead trees, production of a large number of beetles during the end of host utilization may enhance the likelihood of some beetles locating new hosts.

Researchers interested in obtaining beetles for ex perimentation should collect the lower sections of recently killed birches. This practice will minimize the time re quired to obtain large numbers of beetles for experimentation.

Information about buprestid-host relationships is limited. More studies are needed to understand colonization dynamics, including oviposition preferences, factors that influence larval success, beetle effects on host trees, and the efficiency of this borer in utilizing its food resource.

Host quality is probably the most important factor in deter mining success of borer larvae in woody plants. However, biotic and abiotic factors contributing to borer suscep tibility have not been elucidated. 40

III. Predicting Adult Emergence by Heat Unit Accumulation

Materials and Methods

Adult emergence was monitored in Columbus and Wooster,

Ohio from 1981 through 1983. Four A. anxius-infested Eu ropean white birch, Betula pendula Roth, were located and felled in each locality. Tree selection was based upon 50% or more top dieback and presence of previous adult emergence holes or larval galleries. DBH of bolts varied from 8 to 18 cm. The bottom 1.8-2.1 m bolt of each trunk was anchored vertically in the ground to a depth of 25 cm and observed for adult emergence in each locality. New emergence holes were counted daily from first adult emergence until 2 weeks after the last emergence hole was found.

Rearing A. anxius under controlled conditions to deter mine a developmental threshold for the emergence model was avoided by evaluating selected base temperatures from 0 to

12° C and several starting dates. Arnold (1959) reported that the base temperature resulting in the lowest coeffi cient of variation (CV) of °D was the appropriate base to use in heat summation models. Eight base temperatures were evaluated using a modified Allen's program (1976) to measure the area under a sine curve above the threshold with ampli tude specified by each pair of daily maximum and minimum 41 temperatures. Temperatures were obtained from NOAA weather

stations within 15 km of the study area. Daily °D were cal

culated from 4 arbitrary starting dates: 1 July (previous

year), 1 January, 1 April, and 1 May.

Cumulative % adult emergence at each of the two locali

ties was plotted against a od scale for incorporation into a predictive model. Due to the sigmoidal distribution of

these data, ©D were transformed to log^o an<3 cumulative %

emergence to probit units (Riedel et al. 1976, Potter and

Timmons 1983). A log-probit line was then fitted to the

combined data by least-squares analysis. Predicted dates

for 10% emergence from average °D requirements and lines

estimated by log-probit regression were compared to actual

emergence dates.

Dates predicted by the model using X °D requirements were compared to actual 10% emergence in other Ohio locali

ties not incorporated in the model: Cincinnati 1982;

Painesville 1981, 1983; Wooster 1979, 1980.

Results and Discussion

Adult A. anxius emergence varied according to location and year in Ohio (Figs. 2 and 3). First emergence was ob served as early as 5 May (Columbus-1981) due to a warm spring and as late as 3 June (Columbus-1981). First borer Figure 2. Daily temperature and % A. anxius emergence in Columbus, Ohio, 1981 through 1983.

42 diva w m nr m

v v < A y -

* y » '' v'-• / - - \ A/ // M J i \ \ ■■■■ - n , v : \ / v ' iV 'i’\ r / \. .■* \ ■ ,/\ / \ ,-\ N . - • i/> v (i?^K!gui\N'W I* V 3> • j w ^ y a a « A v / w . \. a u y •■I. \ v 'V 7 'p^ •'/ /I A-; -• Ii -v ./ v v*

* -I » I » — i---- 1---- 1---- t- t -1 -1 -i > 1 _l I 1 » Figure 3. Daily temperature and % A. anxius emergence in Wooster, Ohio, 1981 through 1983.

44 • /o EMERGENCE VC. DAILY A TEMPERATURE (®C) i c c St JULIAN DATE 46 emergence differed by 2 and 5 days at 2 sites for Wooster in

1981 and 1982, respectively (Nielsen and Akers, unpublished).

Four starting dates and 8 potential base temperatures were compared for predicting 10% adult emergence. For

Columbus, the base temperature of 8© C (46.4°F) and the starting date of 1 May gave the lowest CV, 3.4, with an average of 255.2od. For Wooster, the base temperature of

10o c (50OF) and starting date of 1 April gave the lowest

CV, 3.7, with an average of 235.7°D (Table 9). The dif ference in base temperatures and starting dates for generat ing the lowest CV's for the 2 Ohio localities may not be surprising. Plant phenology in Columbus is advanced ca. 10-

14 days compared to Wooster (Nielsen's personal observa tions) , so beetle populations are subjected to different rates of climatic change.

Lines estimated by log-probit regression for cumulative borer emergence in Ohio are presented in Figs. 4 and 5. A correlation coefficient (r) of 0.89 and regression equation,

Y = 6.5X - 10.97, for Columbus, and a correlation coeffi cient (r) of 0.93 and regression equation, Y = 14.2X - 29.9, for Wooster, indicate a reasonable fit of the calculated Table 9. Comparison of coefficient of variation for 10% A. anxius emergence in Ohio. Eight base temperatures and 4 starting dates were used for calculations.

Starting Base temperature (OC) Location date 0 4 6 7 8 9 10 12

Jul 1 8.2 8.9 9.2 9.4 9.7 10.0 10.5 11.7

Jan 1 12.6 13.2 13.2 13.1 12.9 12.6 12.5 13.0 Columbus Apr 1 14.9 15.3 15.1 15.4 15.3 15.6 16.2 17.8

May 1 10.6 7.1 4.8 3.8 3.4* 4.3 6.2 12.2

Jul 1 6.7 5.8 5.0 4.8 5.2 4.4 5.3 6.9

Jan 1 14.6 12.5 13.1 9.7 11.0 9.9 6.5 5.7 Wooster Apr 1 11.9 8.9 9.3 5.5 6.7 5.3 3.7* 6.5

May 1 20.6 19.3 18.8 18.6 18.5 18.8 18.8 20.2

* Base temperature and starting date yielding the lowest CV. Figure 4. Linear regression of cumulative percent emergence of anxius vs oD ^ based on Columbus, Ohio, emergence. Oq were computed from 1 May at 8° C base temperature.

48 00 PROBIT (y)= 6.5 x-10.97 99 r= 0.89

UJ 98 95

6.0 80

60 £ 50 50 it1 40 PROBITS »- 30 < _J 20 4.0

x -I98I

2.2 2.32.4 2.5 2.6 2.7 2.8

LOGkj DEGREE DAYS AT 8 ° C BASE Figure 5. Linear regression of cumulative percent emergence of A. anxius vs oD^ based on booster, Ohio, emer gence. c>q were computed from 1 April at LOO C oase temperature.

50 "D 35 CD ro <0 u> <0 PROBITS ro tr CUMULATIVE °/o EMERGENCE

lines to the data. The regression equations gave a proj

ected OD requirement of 189.6 and 233.1 for 10% emergence in

Columbus and Wooster, respectively.

Table 10 compares mean (X) od and regression to actual day of 10% adult emergence. Although there was no signifi cant difference between actual and predicted A. anxius emergence dates (ANOVA, P 0.05), mean deviation from actu al emergence was greater using the regression method (=3.8 days) than X od (=1.0 day).

Table 11 compares predicted 10% emergence cates by the

X od method to actual 10% emergence in Ohio localities and years not incorporated into the model. Since Cincinnati is south of Columbus, emergence was predicted using parameter values of the Columbus model; Painesville is north of

Wooster, so the Wooster model was used for this prediction.

The mean deviation between actual and predicted emergence in all locations and years was 1 day. Therefore, the models can be used to predict bronze birch borer emergence through out Ohio.

These models can be used by arborists and landscape managers to optimize timing of insecticidal sprays to reduce bronze birch borer attack and damage. The current target first spray date recommended for Columbus is 6 May (Julian

Date 12b); for Wooster, the recommended spray date is 20 May 53

Table 10. Julian dates of actual 10% A. anxius emergence compared to predicted emergence based on X o d and linear regression models.

Actual Prediction!/ Location Year emergence X °d Regression

Columbus 1981 154 153 147

Columbus 198 2 143 143 138

Columbus 1983 156 157 148

Wooster 1981 150 152 151

Wooster 1982 145 144 144

Wooster 1983 163 162 ' 162

Mean deviation 1.0 3.8

!/ Columbus °Q computed from May 1 at 8°c base temperature. Wooster °d computed from April 1 at i o ° C base tempera ture. One-way aNOVa indicated that actual and predicted days by x Op or regression were not significantly dif ferent at P < 0.05. 54

Table 11. Julian dates of actual and predicted 10% emer gence of A. anxius adults in Ohio localities and years not incorporated into predictive models.

Actual Predicted emergence^/ Location Year emergence by x°D

Cincinnati 1982 139 140

Wooster 1979 154 154

Wooster 1980 156 152

Painesville 1981 154 153

Painesville 1983 161 16 2

Mean deviation 1.0 i/ Cincinnati prediction based on Columbus model of x °D = 255.2°D. Wooster and Painesville predictions based on Wooster model of x °D = 235.7°D. 55

(Julian Date 140) (Miller and Nielsen 1981). This rep

resents a mean deviation of 19 days when compared to actual

emergence (Table 12). Although reliance on calendar dates

for spraying, coupled with 3 applications at 2-week inter vals, may provide acceptable control during most years,

timing based on our predictive models will be more precise and can be expected to provide consistent results, even during years of unseasonable temperatures.

This study was designed to develop a predictive model for bronze birch borer emergence in Ohio, but the technique described can be used for other insects and localities.

Fine tuning of threshold temperatures and starting dates may be required for accurate prediction of A. anxius emergence

in other parts of its range. This approach may provide an

important tool for improving insect control in nursery pro duction and landscape maintenance. 56

Table 12. Julian dates of actual 10% A. anxius emergence compared to recommended spray date.

Recommended Time Actual spray difference Location Year emergence date—/ (days)

Columbus 1981 154 126 28

Columbus 1982 143 126 17

Columbus 1933 156 126 30

Wooster 1981 150 140 10

Wooster 1982 145 140 5

Wooster 1983 163 140 23

Mean deviation 18.8

Miller, R. L., and D. G. Nielsen. 1981. Insect and mite control on woody ornamentals. Ohio Coop. Ext. Serv. Bull. #504, 63 pp. 57

IV. Host and Host Quality Influences on Reproductive Biology

Materials and Methods

Infested birch, Betula sp., were felled in the Wooster vicinity and placed in a screenhouse insectary at The Ohio

State University, Ohio Agricultural Research and Development

Center (OSU-OARDC), Wooster. Newly emerged, unmated A. an xius beetles were collected daily and separated by sex.

Host influence on adult biology was investigated by caging virgin beetle pairs on leaves of selected trees on the OARDC campus. Beetles 1- to 2-d-old were caged on attached leaves in 19.2 cm3 transparent plastic petri dishes with tops and bottoms partially replaced with nylon mesh to provide ven tilation. Cages were examined at least every other day for eggs and dead beetles. When eggs were found, beetles were moved to new cages. Cages with eggs were positioned in the interior of a tree canopy and examined daily for egg eclosion.

Reproductive Biology of A. anxius on Selected Hosts

In 1980, 25 ^eetle prs, 5 prs/30-cm-tall cutting or seedling (birch), were placed on each of 5 Populus generosa

A. Henry, cottonwood, P. deltoides Bartr. ex. Marsh, and 58

Betula sp. in a polyhouse. In 1981, 10 prs were placed on * * individual, mature P. deltoides and European white birch,

Betula pendula Roth. In 1982, 15 prs were placed on indi vidual, mature B. pendula, pin oak, Quercus palustris

Muenchh., Salix elaeagnos Scop., and silver maple, Acer saccharinum L.; 5 prs were placed on each of 3 P. deltoides.

In 1982, a high population of beetles (100+ prs) was main

tained on a single 3. pendula (ca. 4.2 mtall, 8.5 cm DBh).

In 1983, 15 prs were placed on individual, mature £. palus tr is and S. elaeagnos, and 5 prs were placed on each of 3 P. deltoides and B. pendula.

In 1983, foliage consumption by each beetle pr was determined from leaf tracings processed with a LI-COR 3000

Area Meter. Consumption by individual beetles was calcu lated by dividing total leaf area (cm2) or mg dry wt consumed/pr by total days of male and female feeding. Leaf area and mg dry wt consumed per beetle per host were an alyzed by 1-way ANOVa (P < 0.05).

Inducible Defense Response in B. pendula to Herbivory

In 1983, trees without top dieback, A. anxius larval galleries, or emergence holes were selected in a 2 acre planting of birch at the OARDC. Three trees were chosen randomly from border trees for each of 2 foliage treatments: 59 control (no defoliation); artificial defoliation which con sisted of excising with scissors the apical half of every other leaf on branches within 2 m of the ground (= ca. 25% defoliation). Two other foliage treatments were examined: natural defoliation which consisted of 100 beetle prs feed ing on a single tree; and first-year seedlings. Five beetle prs were fed on each control tree; 10 beetle prs were fed on each artificially defoliated tree— 5 prs on excised leaves ("cut") and 5 prs on leaves not excised ("uncut"); 10 beetle prs were monitored out of the 100 beetle prs feeding on the naturally defoliated tree; and 1 beetle pr was fed on each of 16 first-year seedlings.

In 1984, similar treatments were imposed upon B. pendu la trees. Tree selection was made as described for 1983.

Four trees/treatment were chosen randomly for 1 of 3 foliage treatments: control with 3 to 4 branches enclosed with 7.9 x 7.9 cm2 (20 x 20 in2) clear Chicopee saran fabric to pre vent uncontrolled defoliation, 5 beetle prs/tree; artificial defoliation as in 1983, 5 beetle prs/tree; and natural de foliation involving 1 beetle pr monitored per 10 beetle prs feeding on a single branch, 50 prs/tree. One beetle pr was also fed on each of 8 2-yr-old seedlings. An additional foliage treatment was examined— 5 beetle prs were fed on each of 5 trees defoliated manually 100% in July and August,

1983. 60

Phytochemical Analyses of B. pendula Leaves Subjected to Herbivory

Leaf chemistry was examined for trees in all defolia

tion treatments in 1984; seedling treatments were not an

alyzed. Eight leaves, 2 from each tree quadrant, were

removed from branches 1 week prior to beetle placement and 2

more times at 3 week intervals from the initial sampling

date. Leaves were immediately submerged in liquid N2 and

placed on dry ice until they were stored in a walk-in freez

er ( - 1 6 0 C) at the OARDC. Leaf samples were taken between

9:00 - 11:00 a.m. DST on bright, sunny days. Leaves were

lyophilized, hand ground, and extracted in 20 cc centrifuge

tubes with 5 ml 70% acetone:30% de-ionized H2 O per 100 mg

leaf dry wt in a 40° C water bath for 24 hrs. Subsequently,

5 ml de-ionized H2 O per 100 mg leaf dry wt were added to the

tubes followed by centrifugation (table top - International

Model HN) for 4-6 min at maximum rpms. Tubes were capped ana leaf extract stored at 4-5o C for 3 weeks until phyto chemical analyses were conducted. The following leaf traits were examined: % moisture, total phenols (A.O.A.C. 1955,

Swain and Hillis 1959, Schultz et al. 1981, Schultz and

Baldwin 1982), hydrolyzable tannins (Bate-Smith 1977,

Schultz and Baldwin 1982), condensed tannins (Bate-Smith

1975), tanning coefficient (Bate-Smith 1973, Schultz et al.

1981), and total proteins (Robinson 1979). Leaf traits between foliage treatments were analyzed by 1-way ANOVA 6 1

(P < 0.05). (See Appendix for details.) Means were sepa

rated with Duncan's (1955) new multiple range test (P =

0.05).

Influence of Changing Cage Location on Beetle Reproductive Biology

In addition to defoliation experiments, beetle cages

were moved at various intervals to new leaves in 1984 to

simulate "natural" beetle movement during maturation feed

ing. Five different temporal cage movements were examined

on each of 20 B. pendula trees: cages were moved 3 times/

day (8:00 a.m.-noon-8:00 p.m. DST); 2 times/day (8:00 a.m.-

4:00 p.m. DST); daily (noon DST); every 2 days; every 3

days.

Comparisons of adult longevity, fecundity, length of

maturation feeding period, incubation period, and egg

viability on different hosts, from 1980 through 1934, were

analyzed by Student's t-test or 1-way ANOVA. Comparisons of

adult longevity and fecundity for inducible defense response

and cage movement experiments were analyzed by 1-way ANOVA.

Since within-plant variation is probably as high as between plant variation (Schultz 1983; Schultz et al. 1982, Whitham

1981, 1983; Whitham and Slobodchikoff 1981), the number of

trees usea in the experimentation was not considered in the 62

analyses. Instead, each beetle pr was considered an ex

perimental unit. Means were separated by Duncan's (1955)

new multiple range test (P = 0.05).

Results and Discussion

Reproductive Biology on Selected Hosts

Longevity. Reproductive biology varied significantly with host and between years, in some cases. In 1980, when beetles were caged on seedlings or cuttings, male and female

longevity varied significantly with host (Table 13). Males

lived 4 days longer and females at least 3 days longer when

fed birch instead of poplar. Females lived significantly longer than males on birch (P < 0.10) and cottonwood (P—

0.05) (Student's t-test). In 1981, when beetles were caged on attached, mature leaves of B. pendula and P. deltoioes, host did not influence female longevity (Table 13).

In 1982, both sexes lived longest on P. deltoides, 38 ana 4b days for males and females, respectively (Table 13).

In 1983, females lived longest (28 days) on P. deltoides, while males lived longer on P. deltoides (17 days), and Q. palustr is (15 days) than on B. pendula (11 days) or S. elaeagnos (10 days) (Table 13). Overall, longevity was greater in 1982 than in 1981 or 1983. Early emergence Table 13. Longevity and length of maturation feeding period of A. anxius on selected trees near Wooster, OH, during 1980 through 1983.

Study Plant!/ X Longevity ± S.D. (days)2/ X Days to lstl/ date host oviposition ± S.D. cf ?

June, 1980 Betula sp. 19 ± 4a 22 + 5*a 15 ± 2a Populus deltoides 15 ± 3b 19 + 2*b 15 ± la P. qenerosa 16 ± 4b 17 + 3b 15 ± la

June, 1981 B. pendula --- 27 + 14a 12 ± 6a P. deltoides --- 19 + 9a 14 ± 5a

May-June, B. pendula 14 + 3d 22 + 7*c no oviposition 1982 P. deltoides 38 ± 10a 46 + 10+a 25 + 5a Quercus palustris 20 ± 5b 36 + 7*b 20 ± 5a Salix elaeaqnos 19 ± 5 be 35 + 12*b 24 + 0a Acer saccharinum 15 ± 3cd 20 + 3*c no oviposition

June, 1983 B. pendula 11 + 2b 15 + 4*c 10 ± la P. deltoides 17 + 7a 28 + 9*a 16 + 6a Q. palustris 15 + 4a 19 + 6*b 14 ± 0a S. elaeaqnos 10 + 2b 15 + 5* be no oviposition k/ In 1980, A. anxius adults were fed on attached leaves of Betula seedlings and Populus spp. clonal cuttings; in 1981-1983, adults were fed on attached leaves of mature trees.

2/ Means/sex/year followed by. the same letter are not significantly different at the P = 0.05 level (Duncan's fl955j new multiple range test) for 1980, 1982, and 1983 data; Student's t-test (P < 0.05) for 1981. * or + indicate significant dif ferences between sexes per host at P < 0.05 or P < 0.10, respectively, according to Student's t-test.

1/ Means/year followed by. the same letter are not significantly different at the P = 0.05 level (Duncan's |l955| new multiple range test). 64

stimulated by unseasonably warm temperatures in May, fol

lowed by cool weather in June, undoubtedly contributed to

increased beetle longevity in 1982. In similar studies,

beetle longevity was reported to be 23 days (Balch and Pre-

bble 1940) and 24 days (Barter 1957).

Fecundity. In 1980, significantly fewer eggs were pro

duced by females fed P. generosa (1.1 eggs/? ) than those

fed Betula sp. (4.4 eggs/ ?) or P. deltoides (3.3 eggs/? )

(Table 14). Fecundity comparisons only of ovipositing fe males indicated no significant host influence (P 5 0.05,

Table 15). Only 11% of the females fed P. generosa

oviposited, whereas 71% and 50% of those fed betula sp. and

P. deltoides, respectively, oviposited. Barter (1957) re ported that A. anxius females probably produce an average of

25 eggs. Low fecundity in our study may be attributed to

feeding beetles on first year seedlings or cuttings and/or higher greenhouse temperatures that may have stressed bee tles. In 1981, females fed B. pendula were more fecund (19 eggs/? ) than those fed P. deltoides (o eggs/? ) (Table 14).

Results from 1980 and 1981 suggested that Betula was a nominal host for bronze birch borer adults.

Surprisingly, females fed B. pendula in 1982 did not reproduce (Table 14). What appeared to be a nominal adult Table 14. Boat Influences on A. anxlus fecundity and egg incubation period near Booster, OH., during 1980 through 1983.

X Fecundity i S.O. 2 / X Ho. eggs!/ _ Study Plant!/ i Fecundity!/ of ovipositing 9 's hatched £ S.D./ X Days to5/ date host i S.D. (No. » *s) (Ho. 9 's) v ovipositing 1st hatch ± S.D.

June, 1980 Betula sp. 4 + 6 (17) a 6 + 6 (12) a -- -- Populus deltoides 4 T 5 (24) a 7 + 4 (12) a -- -- P. qenerosa 1 ♦ 3 (18) b 10 + 5 ( 2) a -- --

June, 1981 B. pendula 19 + 17 (12) a 25 + 15 ( 9)a 11 ± 9a P. deltoides 6 + 11 (16) b 9 + 12 (10) b 2 ± 6b

May-June B. pendula 0 (15)c 0 -- __ 1982 P. deltoides 11 + 8 (12) a 12 + 7 (11) a 3 ± 3a 15 ± 2b Quercus palustrls 4 + 6 (13) b 8 + 6 ( 7)a 4 ± 4a 25 ± la Salix elaeagnos 2 + 5 (13)be 11 + 7 ( 2)a 4 ± la 14 ± 3b Acer saccharlnum 0 (14)c 0 -- --

June, 1983 B. pendula 2 + 6 (15) b 6 + 9 ( 4) a 4 ± 7a 13 ± 4a P. deltoides 16 + 10 (13) a 17 + 9 (12) a 7 ± 7a 15 ± 5a Q. palustrls 1 + 4 (14) b 10 + 2 ( 2)a 3 ± la 18 ± (a S. elaeagnos 0 (12) b 0 0

1/ In 1900, A. anxlu8 adults were fed on attached leaves of Betula seedlings and Populus spp. clonal cuttings; in 1981-1981, adults were fed on attached leaves of mature trees.

2/_5/ Heans/year followed by the sane letter are not significantly different at the P • 0.05 level (Duncan's |1955| new multiple range test) for 1980, 1982, and 1983; Student's t-test (P < 0.05) for 1981. Data for 1980 transformed to Log^o (X + 1) for analysis. Numbers of females vary from test due to insects escaping from cages. host in 1980 and 1981 proved unsuitable in 1982. We hypoth

esize that caging a high density beetle population (200+) on

leaves of a single tree may have induced a defensive

response within the host. Partial defoliation by herbivores

has been demonstrated to reduce leaf quality in Alnus rubra

Bong and Salix sitchensis (Rhoades 1983), Quercus rubra L.

(Schultz and Baldwin 1982), and Betula pubescens ssp.

tortuosa Ledeb. (Haukioja and Niemela 1977). Feeding by

herbivores was not controlled on any of our test trees, and

we did not monitor abundance of A. anxius adults in the ex

perimental area. Based on our unpublished observations of

beetle density, in infested birch plantings in nurseries and

landscapes, however, we would not expect to find as many as

200 beetles feeding on an individual tree naturally. Beetle

sightings in the birch study area were rare until 1983 when

200 beetles were collected from tree trunks during a 2-h period. Placement of 200 beetles on a small birch tree was probably sufficient stimulus to elicit an inducible chemical

defensive response from the host. Haukioja and Niemela

(1977) reported an inducible defensive response in B. pubes cens ssp tortuosa when fed upon by larvae of a geometrid moth. The fluctuations we observed in the reproductive biology of A. anxius on B. pendula may be explained by in ducible defenses. In 1982 and 1983, significantly more eggs were produced by beetles fed P. deltoides. But, again, when fecundity of only ovipositing beetles was compared, there were no dif ferences between hosts. Again, the percent of females ovipositing was influenced by host. Ninety-two percent of the females fed P. deltoides oviposited, whereas 53% and 15% of those fed Quercus or Salix oviposited, respectively. In

1983, feeding trials were repeated with lower beetle densi ty. More eggs were produced by the female cohort on P. del toides, but fecundity of ovipositing females was not sig nificantly influenced by host (Table 14). Ninety-three per cent of the females fed P. deltoides oviposited, whereas 27% and 14% of those fed B. pendula and £. palustris oviposited, respectively. Fewer beetles fed Q. palustris oviposited in

1983 than 1982, but fecundity of ovipositing females and egg hatchability were similar. Beetles fed S. elaeagnos failed to oviposit in 1983.

Foliage consumption was higher for beetles fed P. del toides and palustris than B. pendula or S. elaeagnos (P =

0.05,Duncan's 1955i new multiple range test) (Table 15).

There was no difference, however, in egg production per unit of foliage consumed on any of the hosts. Female foliage consumption per day is probably greater than indicated.

Since beetles were usually paired, consumption was assumed to be equal for purposes of analyses, but females Table 15. Foliage consumption per A. anxius adult on selected hosts near Wooster, OH, in 1983.1/

X Leaf area consumed X Eggs per cm2 X Eggs per mg Plant per day ± S.D leaf consumed leaf consumed host cm2 mg (dry wt) per day ± S.D per day ± S.D.

Populus deltoides 0.28 ± 0.12a 1.50 ± 0.44a 0.024 ± 0.022a 0.13 ± 0.14a

Quercus palustris 0.30 ± 0.22a 1.69 ± 0.91a 0.036 + 0.001a 0.32 ± 0.15a

Betula pendula 0.14 + 0.06b 0.68 ± 0.34b 0.049 ± 0.038a 0.22 ± 0.17a

Salix elaeaqnos 0.10 ± 0.06b 0.45 ± 0.41b 0.0 0.0

1/ Means/column followed by the same letter are not significantly different at the P = 0.05 level (Duncan's [1955] new multiple range test). Data for X eggs/cm2 leaf or rag leaf consumed are for ovipositing females.

oo 69 are larger than males (X ? wt = 22 mg, a = 19 mg; n = 10) and probably require more energy, especially for egg produc tion and oviposition.

Maturation Feeding. In all test years, average days to first oviposition (Table 13) did not vary significantly with host, according to ANOVA (P < 0.05). The shortest matura tion feeding period recorded was 7 days (1981). In similar studies, oviposition did not occur until at least 6 days after adult emergence (Barter 1957, Williams and Neiswander

1959). The range in average days to first oviposition between years for a particular host indicated that environ mental conditions influenced the length of the preoviposi- tion feeding period.

Egg Incubation and Viability. Average days to first egg hatch was influenced by host only in 1982. Eggs pro duced by females fed 2* palustris required significantly longer to hatch (Table 14). Host influence on percent egg hatch was significant only in 1981. Hatch was higher for eggs from females fed Betula than Populus foliage (Table

14) .

Inducible Defense Response in B. pendula

In 1983, A. anxius males lived significantly longer, 11 days (P < 0.05), when fed foliage from undefoliated control 70 trees; females lived significantly longer (P < 0.05) when fed foliage from control trees, 15 days, and seedlings, 13 days (Table 16). More importantly, 27% of females on con trol trees oviposited (2.1 eggs/? ) whereas, those fed on trees with any other defoliation treatment failed to oviposit. In 1984, there was little difference in beetle reproduction on control trees versus other treatment trees

(Table 17). There was no significant difference in female longevity when fed foliage from control trees compared to other tree treatments. Percent females ovipositing when fed control leaves was lower in 1984 (10%) than 1983, (27%); there was no significant difference (P <0.05) in number of eggs deposited between tree treatments. In fact, oviposition was extremely low in 1984 (0 to 0.4 eggs/? ) when compared to 1981 (19 eggs/? ). There was a noticeable but unquan tified increase in herbivory in the birch study area in 1983 and 1984. By 1984, control trees were probably not true controls but more similar to other tree treatments in terms of herbivory.

Long-lasting herbivore defense response has been demon strated in paper birch, B. papyrifera, by Werner (1979) .

Immediately inducible defenses in mountain birch, B. pubescens ssp. tortuosa, were reported by Haukioja and Niemela

(1977). B. pendula probably was responding to past and Table 16. B. pendula lea£ treatment effects on A. anxius adult longevity and reproduction in 1983 near Wooster, OH.

Leaf X Lonqevity + S.D. (Days)1/ % ?'s treatment ovipositing X No. eggs/? d ?

Control 10.7 + 2.2a 14.7 ± 3.8*a 26.7 2.1

Natural Defoliation

-100 prs 6.3 ± 1.5c 10.0 ± 5.9bc 0.0 0.0

Artificial Defoliation

- Leaf Cut 6.5 ± 1.2c 8.4 + 1.9*c 0.0 0.0

- Leaf Uncut 8.2 ± 1.3b 9.25 ± 1.9c 0.0 0.0

Seedlings 8.9 ± 2.6b 12.6 ± 6.l*ab 0.0 0.0

1/ Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Duncan's 11955]new multiple range test).

* Longevity between sexes/treatment was significantly different according to Stu dent's t-test (P < 0.05). Table 17. B. pendula leaf treatment effects on A. anxius adult longevity and reproductive biology in 1984 near Wooster, OH.

Leaf X Lonqevity + S.D. (days)l/ % ? 1 s treatment a ? ovipositing X No. eggs/?

Control 12.4 ± 3.0a 14.4 ± 3.lab** 10.0 0.15a

Natural Defoliation

- 50 beetle prs 10.9 ± 2.8ab 16.2 ± 2.1a* 11.8 0.35a

Artificial Defoliation

- Leaf Cut 10.8 ± 1.2ab 13.0 ± 2.8b* 10.0 0.40a

- Leaf Dncut 10.5 ± 2.7b 12.9 ± 5.2b 5.6 0.11a

Defoliation (ca. 25%) previous year 12.2 ± 1.8a 15.8 ± 1.6a 5.3 0.32a

Seedlings 10.8 ± 1.5ab 16.1 ± 3.7a* 0.0 0.0a

Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Duncan's 1955| new multiple range test).

* Longevity between sexes/treatment were significantly different according to Student's t-test (P ^ 0.05); for control treatment, P = 0.055. 73 present herbivory, confounding the results from experimental trees, at least during 1984.

Phytochemical Analyses of B. pendula Leaves Subjected to Herbivory

There were few significant differences detected in leaf traits between foliage treatments (Table 18). By the third sampling date, foliage from the artificially (A) defoliated trees contained significantly less condensed tannins, but had a significantly greater capacity to precipitate proteins

(tanning coefficient) than the other foliage treatments.

Martin and Martin (1982) reported that correlation does not have to occur between phenolic or condensed tannin content with tanning ability (at least in the 6 oak species examined by them), but when condensed tannins were significantly dif ferent between treatments, so was the tanning coefficient.

Although artificially defoliated trees had a significantly greater capacity to precipitate proteins by the third sam pling date, the tannins responsible for this increase were not detectable by the determination method (CONC. HC1. in butanol) employed (Swain and Hillis 1959, Broadhurst and

Jones 1978). There were no significant differences between foliage treatments determined in the other leaf traits:

% moisture, total phenols, hydrolyzable tannins, or total proteins. Table 18. B. pendula leaf traits assayed on 3 sampling dates during 1984. Values are X ± S.E.

Leaf 1/ Leaf 2/ Sampling datel/ trait type 4 June 25 June 23 July

Moisture (%) c 64.2 + 1.5a,1 62.4 + 0.9 ab,1 59.0 + 0.9b,1

A 63.2 + 0.8a,1 58.9 + 0.9b,1 54.9 + 1. 3c,1

N 62.2 + 1.4a,1 58.6 + 0.67b,1 56.2 + 0.7b,1

P 63.7 + 1.5a,1 65.2 + 2.8a,l 58.6 + 1.9a,1

Total Phenols C 8.3 + 0.6a,1 7.0 + 0.8a,1 8.4 + 2.la,1 (mgTA/ml leaf extract) A 7.4 + 0.5a,1 7.8 + 0.6a,1 9.7 + 1. 9a,1

N 7.9 + 0.4a,1 8.0 + 0.6a,1 7.2 + 0.8a,1

P 8.6 + 0.4a,1 8.7 + 2.0a,1 7.4 + 0.6a,l

Hydrolyzable Tannins C 1.6 + 0.5a,1 0.8 + 0. 2 a, 1 0.9 + 0.4a,1 (mgTA/ml leaf extract) A 1.8 + 0.5a,1 1.6 + 0.4a,l 1.7 + 0.4a,1

N 2.4 + 0.3a,1 0.9 + 0.8b,1 0.9 + 0.lb,1

P 2.2 + 0.3a,1 0.9 + 0.2d ,1 1.0 + 0. 3b, 1 Table 18. Continued

Leaf 1/ Leaf 2/ Samplinq date3/ trait type 4 June 25 June 23 July

Condensed Tannins C 1.0 ± 0.3a,1 0.4 ± 0.la,1 0.3 ± 0.1a, (mgQT/ml leaf extract) A 1.1 + 0.3a,1 0.8 + 0.2a,1 0.0 + 0.2a,

N 1-4 + 0.la,1 0.5 ± 0.lb,1 0.5 ± 0.lb,1

P 1.2 + 0.2a,1 0.5 + 0.lb,1 0.4 ± 0.2b,1

Tanning Coefficient C 0.7 ± 0.4a,1 0.4 + 0.2a,1 0.2 + 0.la,1 (mgTA/ml leaf extract) A 0.9 ± 0.3a,1 0.7 ± 0 . la, 1 1.0 + 0.1a,2

N 0.8 ± 0.2a,1 0.4 ± 0.la,1 0.4 ± 0.la,1

P 0.8 + 0.2a,1 0.3 ± 0.la,1 0.4 + 0.1a,l

Cn Table 18. Continued

Leaf 1/ Leaf 2/ Samplinq date!/ trait type 4 June 25 June 23 July

Total Proteins c 0.2 ± 0.04a,1 0.2 ± 0.02a,1 0.2 ± 0.03a,1 (mg Protein/ml leaf extract) A 0.3 ± 0.06a,1 0.2 ± 0.03a,1 0.2 ± 0.02a,l

N 0.3 ± 0.00a,l 0.2 ± 0.02b,1 0.2 ± 0.02b,1

P 0.3 ± 0.04a,1 0.2 ± 0.09b,1 0.2 ± 0.01b,1

1/ tA = equivalent amount of phytochemical compound determined in tannic acid standard. QT = equivalent amount of phytochemical compound determined in quebraco acid standard.

2/ Leaf type code: C = control; A = combined leaves, cut and uncut, for artificial de foliation; N = natural defoliation; and P = previous yr defoliation.

2/ Means with the same letter/leaf trait within a row are not significantly different at the P = 0.05 level (Duncan's [1955] new multiple range test). Means with the same number/leaf trait within a column are not significantly different at the P = 0.05 level (Duncan's [1955 ] new multiple range test). 77

Significant differences in leaf traits were determined

within foliage treatments. Seasonal % moisture decreased

significantly within all treatments except for those trees

previously (P) defoliated in 1983. These seasonal trends

were similar to those reported by Haukioja et al. (1978) and

Schultz and Baldwin (1982). There was no significant dif

ference in measured total phenols within treatments, but

there was a decrease seasonally in hydrolyzable and con densed tannins. Significantly less hydrolyzable and con densed tannins occurred in naturally (N) and previously (P) defoliated trees in 25 June and 23 July samples than in ini

tial samples on 4 June. Seasonal trends in total protein

indicated a significant decrease in naturally and previously defoliated trees by the second and third sampling dates.

Haukioja et al. (1978) found nitrogen in mountain birch leaves was highest in the spring, decreased some and leveled off during summer months, and decreased rapidly in the fall.

I found no seasonal differences of total protein in control

(C) or artificially defoliated trees, however, the last sam pling date was 23 July before nitrogen content would be ex pected to decrease.

Leaves contain complex combinations of phytochemicals that influence herbivory. Polyphenolic compounds, including hydrolyzable and condensed tannins, and the ability to bind 78 proteins (tanning coefficient) are implicated as phytochemi cal compounds that reduce and retard herbivore feeding by creating tougher leaves, increasing astringency, forming insoluble complexes between proteins, or inhibiting diges tive enzymes (Feeny 1969, 1970, Rhoades and Cates 1976).

Scriber (1977) found that low moisture retarded growth of insects. Nitrogen, as indicated by total proteins, is ex tremely important to herbivores in metabolic processes, cel lular structure, and genetic coding (Mattson 1980). There were few significant leaf trait differences, however, between foliage treatments. These results are not surpris ing since the reproductive beetle bioassay of the same foliage treatments were also insignificant (Table 17). In

1984, birch trees used for experimentation did not appear to respond defensively to any defoliation treatment, yet, bee tle fecundity was lower in 1984 than in other years. Ex perimental trees may have been stressed sufficiently so they could not respond defensively. Furthermore, beetles feeding on these trees may have been nutritionally impoverished.

Cage Movement Influence on Reproductive Biology

Cage movement experiments tended to substantiate the hypothesis that B. pendula trees 'in the study area were in a defensive mode to herbivory. Moving cages to new leaves at variable intervals did not significantly influence male or 79

female longevity or fecundity (Table 19). Although the % of

females ovipositing and number of eggs produced were greater

in cage movement studies than in the defoliation experiments

in 1984, there was no significant difference in fecundity between females ovipositing, 1.5 eggs in the cage movement experiment (moved daily), versus females fed on control trees ovipositing 0.15 eggs in the 1984 defoliation experi ments (P = 0.11, Student's t-test). Fecundity was extremely low in all tests in 1984 regardless of the frequency of cage movement or degree of defoliation.

In 1982 and 1983, birch did not provide the best quali ty foliage for beetle reproduction. This may be a reflec tion of the experimental procedure. Endemic beetle popula tions continued to increase in the study area, and other herbivores were not restricted. Birch foliage quality may have been reduced by herbivory during a given year and by previous defoliation. In addition, beetles were confined in cages and therefore consumed more of a single leaf than they would normally. In nature, beetles notch leaves and are able to move freely, thereby avoiding possible inducible plant defenses such as Haukioja and Niemela (1979) reported for B. pubescens tortuosa. Table 19. Influence of cage movement on A. anxius reproductive biology in 1984.

Cage X Longevity ± S.D. (Days)l/ % ? 's movement cf 9 ovipositing X No. eggs/91 /

3 times/day 11.9 + 2.9a 16.7 + 4.7a* 20.0 1.4 + 3.0a

2 times/day 13.2 + 5.9a 17.1 + 4.2a* 11.1 0.3 + 0.8a

Daily 12.6 + 2.7a 17.5 + 5.0a* 21.1 1.5 + 3.6a

Every 2 days 12.7 + 4.0a 16.8 + 5.5a* 16.7 0.7 + 1.8a

Every 3 days 11.8 + 3.0a 16.4 + 3.5a* 11.1 0.9 + 2.7a

1/ Means within a column followed by the same letter are not significantly different according to ANOVA (P < 0.05).

* Longevity between sexes/cage movement was significantly different according to Student’s t-test (P 1 0.05).

00 o 81 In 1984, beetle bioassay and phytochemical analyses indicated that all birch trees responded similarly to her bivory. Since trees were dying, it is doubtful that this response was defensive. It is possible that repeated at tacks by herbivores had taxed birch tree energy reserves such that they were now poor nutritional resources for bee tle reproduction.

These experiments demonstrate that A. anxius reproduc tive biology is influenced not only by host species but also by host quality. Many variables must be considered when interpreting an insect's reproductive strategy. One such variable is inducible plant defenses. Another is foliage nutrition. More work is needed before we can understand how a plant responds to subtle and obvious stresses, including herbivores, and how changes in a plant's phytochemistry in fluence herbivore life history. 82

V. Mating Behavior

Materials and Methods

Newly emerged, unmated beetles were collected from in fested wood held in an insectary at the OARDC. Beetles were separated by sex and caged communally in crispers containing fresh apple pieces before and after observation periods.

Mating behavior was observed at 28-320 C on a laboratory bench illuminated by four cool-white fluorescent and 2 150- watt bulbs (1.1 x 103 jjl e m~2 s ) . Beetles were observed in inverted 30 cc clear plastic cups, 1 pr per cup, during

2-h sessions between 1:00 and 5:00 p.m. (DST).

Mating Frequency vs Age

.Unmated beetles of the same age, from less than 1- to

5-d-old, were observed periodically to investigate the in fluence of age on propensity to mate. During each observa tion session, at least 5 prs of a given age were observed.

Percent of prs copulating, length of copulation, and time prior to copulation during each 2-h observation period were recorded. One-way ANOVA and Duncan's (19 55) new multiple range test (P = 0.05) were used to assess the effect of bee tle age on these behavioral parameters. 83

Duration of Copulation vs Sperm Transfer

The influence of insemination on subsequent mating be

havior was investigated. Mating pairs were separated after

1 (4 prs) or 3 (11 prs) min of copulation or were allowed to

uncouple naturally (15 prs). Sperm transfer was determined

by dissecting females and examining spermethecae for sperm.

Previous Mating Experience

To determine if previous mating experience influences

subsequent male/female encounters, beetle prs were observed

for a 2-h period after which they were separated. Beetles

that had copulated were then paired again for another 2-h observation period during the next 24 to 48 h. Beetles not copulating were returned to crispers. Mating behavior was observed and recorded as previously described. Percent of

beetles copulating in each category was compared by 1-way

ANOVA. Student's paired t-tests (P = 0.05) were conducted

to determine if previous mating experience influenced other mating parameters. In other trials to test the effects of previous mating experience, mated males were caged with un mated females, and unmated males were caged with mated fe males. Percent of beetles copulating in the 2 groups was compared using Student's t-test (P = 0.05). 84

In another experiment, 26 prs were interrupted after 3 min of copulation, separated for 24 h, and then paired again. Percent of prs copulating, length of copulation, and time from pairing to copulation were recorded during the second pairing. Time prior to copulation and copulation duration between naive and 3-min-interrupted beetles were compared using Student's t-test (P = 0.05).

Influence of Mating Frequency on Reproductive Biology

Females mating 1, 2, or multiple (confined with a male continuously) times were caged on attached, mature leaves of

European white birch, Betula pendula Roth, or cottonwood,

Populus deltoi de s Bartr.ex. Marsh. Two females of each mating frequency were caged singly on 10 trees/host (6 cages/tree) in 19.2 cm3 transparent plastic petri dishes with tops and bottoms partially replaced with nylon mesh to provide ventilation. All trees were located at OARDC.

Cages were moved to fresh leaves and examined at least 6 days/week for eggs and dead females. When eggs were found, beetles were moved to a new cage. Cages with eggs were positioned in the interior of a tree canopy and examined 3 times/week for egg hatch.

Comparisons of female longevity, fecundity, and egg hatch on both hosts were analyzed by 1-way ANOVA. Each caged female was considered an experimental unit. Means 85 were separated at the P = 0.05 level by Duncan's (1955) new multiple range test.

Results and Discussion

Mating Frequency vs Age

Beetle age significantly influenced propensity to copu late. Beetles 2- to 5-d-old had a significantly higher copulation rate, ca. 7X, than beetles less than 1-d-old

(Table 20). Although beetles 1-d-old mated 3X more than beetles less 1-d-old, and 2X less than beetles 2- to 5-d- old, these differences were not significant. However, the most efficient approach for obtaining mated females is to use beetles that are 3- to 5-d-old.

Beetles observed emerging from infested wood outdoors and in the laboratory demonstrated no obvious sexual be havior toward other beetles. Upon emerging, beetles crawled over one another with no apparent interest in courtship.

This behavior is opposite from clearwing borers (Lepidop- tera: Sesiidae) that commonly copulate within 2-h after emergence (Barry and Nielsen 1984).

Duration of copulation was significantly less for 1- to

3-d-old beetles (338-361 sec) than for beetles 4- or 5-d-old

(432 and 419 sec), respectively. Time from pairing to 86

Table 20. Percent of A. anxius beetles copulating at dif ferent ages under laboratory conditions near Wooster, OH.

No. of 2 hr Beetle age observation X « (days) sessions^/ Copulation ± S.D.2/

1 6 3.6 + 4.0 b

1 11 13.5 + 11.9 ab

2 15 27.4 + 17.3 a

3 16 28 .8 + 17.8 a

4 10 30.4 + 21.9 a

5 8 28.5 + 16.0 a

For each session, at least 5 beetle prs were observed/ age group.

.iZ Data were transformed to arcsine sTST before analysis. Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Dun can's [1955] new multiple range test). 87 copulation was not significantly different between age groups (Table 21)*

Duration of Copulation vs Sperm Transfer

Duration of copulation influenced transfer of sperm bundles. When copulation was interrupted after 1 min, no spermethecae contained sperm; at 3 min, only 9% of the spermethecae contained sperm. However, when copulation was un- interrupted, 87% of the females dissected had been inseminated.

Previous Mating Experience

Previous experience had a pronounced influence on the mating behavior of A. anxius. Although Barter (1957) sug gested that mated females avoided second copulation en counters, beetles mated repeatedly in our tests. Beetle age was not a significant factor in the propensity of 2- to 6-d- old beetles to mate a second time. There were no signifi cant differences in duration of copulation between first and second copulations, 444 ± 194 and 491 + 170 sec. (P = 0.36;

X i S.D.), respectively, nor in time from pairing to copula tion 49 ± 24 and 52 ± 41 min (P = 0.75), respectively (Stu dent's t-test for paired comparisons).

Mated males caged with unmated females had a higher copulation rate, 45.0 ± 5.8%, than mated females caged with 88

Table 21. Duration of copulation and tine prior to first copulation of naive A. anxius adults under laboratory conditions near Wooster, OH.

_ X Time prior No. X Copulation to copula- Beetle age matings duration (sec) tion (min) (days) observed + S.D. 1/ + S.D. 1/

*:1 4 337 .7 + 110.8 51.8 + 30.4

1 25 361.0 + 104.lab 50.1 + 31.9a

2 62 347.5 + 88.6b 45.0 + 33.5a

3 50 376.2 + 100.Bab 49 .7 + 35.9a

4 35 432.5 + 174.5a 57.3 + 31.8a

5 3b 419.3 + 160.7a 6 2.2 + 40.2a

Means within a column followed by the same letter are not significantly different at the P = 0.05 level (Dun can's [l955j new multiple range test). Data were trans formed to logiQ (x + 1) before analysis. Beetles < 1-d- ola were not included in the analysis because only 4 matings were observed. 89 unmated males, 29.6 + 8.2%, according to Student's t-test (P

= 0.02). Smith (1970) reported similar results with another tree infesting insect, the peachtree borer, Synanthedon exitiosa (Say) (Lepidoptera: Sesiidae). Regardless of age, mated males caged with virgin females copulated sooner than unmated males caged with virgin females. Males readily mated 2 or more times, but only 58% of the females mated more than once.

Since only 9% of the females that had copulated for 3 min were inseminated, their subsequent mating behavior was examined. These beetles copulated sooner and were more likely to mate during their next encounter with a male.

Eighty-four percent of the "3-min" beetles mated again during their next opportunity, whereas the highest % copula tion for naive beetles was at least ca 2.8 x lower (Table

20). "Experienced" beetles copulated in half the time (33 min) than during their original encounter (66 min) and re mained in copulo for 411 sec. "Naive" beetles courted sig nificantly longer (52 min), but there was no difference in copulation duration (382 sec) (Table 22). Interrupting copulation before sperm transfer resulted in beetles mating sooner at the second meeting. This response would seem to be adaptive. Once mated, egg maturation and location of 90

Table 22. Comparison of copulation duration and time prior to copulation between naive and 3-min-interrupted A. anxius adults under laboratory conditions near Wooster, OH.

X Copulation X Time prior Beetle mating duration (sec) to copulation (min) experience ± S.D.l/ ± S.D.2/

Naive 382.0 ± 128.0 51.8 ± 34.9

3-min 411.3 ± 90.6 33.4 ± 23.8

No significant difference between beetle groups according to Student''s t-test (P = 0.15) •

2/ Significantly different between beetle groups according to Student's t-test (P = 0.0012). 91 sites for oviposition may become dominant drives for fe males, whereas males can contribute most to reproductive success of the species by pursuing additional mates.

Influence of Mating Frequency on Reproductive Biology

Mating frequency did not significantly influence female longevity, fecundity, or egg viability when beetles were fed birch or popular (Table 23). Females mated once were as fertile as females confined continuously with males. Al though we did not examine mating behavior inside leaf cages, we did observe beetles copulating in cages attached to leaves.

Beetle age and mating experience had the greatest im pact on mating behavior. Using unmated females at least 3- d-old and "experienced" males will decrease the time re quired to obtain mated females for experimentation.

i Table 23. Influence of mating frequency on longevity, fecundity, and egg hatachability of beetles fed on 2 host species at Wooster, OH.

X Fecundity + Plant No. X Longevity X Fecundity S.D. of ovi X % egg host matings (days) ± S.D. ± S.D. positing s ’ s hatch ± S.D.

1 16.4 + 4. 4a 1.5 ± 3.6a 5.6 ± 5.5a 11.3 ± 21.8a

Betula pendula 2 16.8 + 5.4a 1.0 ± 1.6a 3.0 ± 1.3a 15.8 ± 20.1a

Multiple 18.0 + 5.4a 1..2 ± 3.5a 7.3 ± 6.5a 23.8 ± 21.8a

1 30.8 + 15.5a 10.3 ± 17 .0a 19.2 ± 19.4a 23.5 + 21.9a

Populus deltoides 2 31.5 + 13.0a 5.2 ± 10.2a 9.1 ± 12.4a 19.6 + 38 .0a

Multiple 32.1 + 11.2a 9.0 ± 13.5a 14.2 ± 14.7a 7.0 ± 11.7a

1/ Means within a column for a host plant followed by the same letter are not sig nificantly different at the P = 0.05 level (Duncan's [1955! new multiple range test).

ro Discussion

The relationship between bronze birch borer and its birch host is complex. This beetle utilizes the tree 2 ways: (1 ) as an adult, it is a foliage feeder; (2 ) as a larva, it is a subcortical feeder. Through this adapta tion, the bronze birch borer has "specialized" and maxi mized its reproductive biology with its birch host.

In feeding trials with adults on trees in the study area (OARDC), birch foliage quality declined, as measured by beetle oviposition (Table 24). In 1981, birch was a nominal beetle host; 75% of the females oviposited an average of 19 eggs. This approached the reproductive potential suggested by Barter (1957). In 1982, however, when 2 0 0 beetles were caged on a single birch tree, no eggs were produced. Females fed on other, nearby host species produced eggs (Tabl* 14). Undoubtedly, increased herbivory on a single birch tree induced a defensive response affect ing beetle reproduction. Haukioja and Niemela (1977, 1979) reported a similar response to herbivory in mountain birch.

In 1983, experiments were designed to investigate this induced defensive response by artificially defoliating some

95 94

Table 24. Oviposition by A. anxius females fed attached B. pendula foliage from 1981 to 1984 in the OARDC oirch study area near Wooster, OH.

Study No. beetles % Females X No. eggs year per tree ovipositing per female

1981 10 75.0 18 .6

1982 1 0 0 0 . 0 0 . 0

1983 5 26.7 2 . 1

1984 5 1 0 . 0 0.15 9 5

birch trees and maintaining high beetle populations on

others. The reproductive biology of the beetles was com pared to that of beetles fed on "control" birch trees (only

5 beetle prs/tree). None of the beetles produced eggs when

fed on artificially or naturally defoliated trees, but 27%

of beetles fed on "control" trees produced eggs. Although

some "control" females reproduced, fecundity was extremely

low compared to 1981.

Several factors influenced the "control" birch trees.

Few beetles had been observed in the study area until 1983 when 2 0 0 + adults were collected from tree trunks in 1 hr.

Herbivory by this increasing beetle density, as well as by other insects, was not controlled. Feeding by these herbi vores may well have induced a response in the "control"

trees. In addition, previous defoliation may have influ enced current foliage quality. Werner (1979) reported re duced larval growth in the spear-marked black moth when larvae were fed leaves from repeatedly defoliated paper birch. Wallner and Walton (1979) reported similar results with gypsy moth, Lymantria dispar (L.), fed oak leaves from previously defoliated trees. Another factor that may have influenced tree quality was reported by Rhoades (1983) and

Baldwin and Schultz (1983) . In separate experiments, they found increases in defensive phytochemicals occurring in 96 undefoliated trees nearby defoliated ones, suggesting

inter-tree chemical communications.

Therefore, the "control" birch trees in the 1983 ex periments probably were not true controls. Instead, these trees were expressing a defensive response as a result of interrelated factors of current defoliation, previous de foliation, and perhaps communication between plants. Con finement of beetles in cages also may have had some effect.

In nature, beetles notch leaves and move freely within and between hosts, thereby avoiding plant defensive compounds

(Haukioja and Niemela 1979, Carroll and Hoffman 1980).

Hence, low fecundity could be due to "control" trees being in a defensive mode and caged beetles unable to avoid these defenses.

In 1984, experiments again were designed to investi gate defensive response in birch to herbivory. Branches on

"control" trees were screened to restrict herbivory; leaves from "control" and defoliated trees were analyzed for de fensive phytochemicals; caged beetles were moved at pre scribed time intervals to fresh leaves on the same trees to simulate natural adult feeding. Fecundity for females fed on "control" trees was low; 1 0 % oviposited with an average of only 0.15 egg/female. There were few significant dif ferences in leaf traits between foliage treatments, in dicating that leaf quality was similar with all trees test ed. Although leaves from trees used in the cage movement experiment (Table 19) were not analyzed for phytochemical compounds, fecundity between caged females that were moved daily and females that were fed "control" foliage was not significantly different. This indicated that all B. pendula used in these experiments were similar in leaf quality.

In all 1984 experiments, a total of 265 females were fed B. pendula foliage; average fecundity was 0.7 egg/female.

Obviously, birch leaf quality decreased from 1981 to 1984.

Also, unlike 1983, beetles were not apparent in the study area in 1984. Though emergence hole counts from trees in the study area indicated that a large adult population had emerged, few beetles were captured with a sweep net or D-

Vac from birch foliage during peak beetle emergence.

Adults must have dispersed, but oviposition obviously took place, since 90 larvae were excavated from 2 birch trees in

September 1984. Other trees in the area were exhibiting symptoms of birch dieback and mortality.

Dispersal could be explained partially by defensive phytochemicals. Another explanation is that beetles dis persed in response to low nutritional value of existing foliage. The beetles that remained were able to choose 98

suitable foliage from B. pendula and the other birch spe

cies in the study area to permit egg maturation.

Larval host utilization is important in this borer/

host relationship. Larval establishment in the study area

was first noticed in late summer/fall 1982. Reproduction

of experimental beetles was low, probably due to high den

sity feeding on a single tree. Although this experiment demonstrated an induced defensive responses in birch, bee

tles must have avoided toxic leaf compounds, since adults emerged from European and other birch trees in 1983. Bee

tle emergence in 1983 indicated that wild beetles in 1982 were able to feed and oviposit. As a result, 1983 endemic beetle density apparently was higher than 1982. Larval establishment was obvious by fall 1983 as birch dieback and dying trees were common. Larval density apparently was

increasing, as 1,124 emergence holes were counted in birch trees in 1983 and 9,404 in 1984 (unpublished data). Fewer beetles, however, were observed in the study area in 1984 than in 1983. As larval establishment increased, it ap peared that adult host acceptance eventually decreased and adults dispersed.

Ball and Simmons (1980) reported that emergence did not occur from healthy trees or trees displaying early de cline symptoms. Low numbers of adults emerged from 99

branches exhibiting dieback. Most beetles emerged from the

trunk and main branches of trees exhibiting advanced die

back symptoms. Mass emergence in the year of tree death

probably maximizes the chance for continuance of the

population at a time when dispersal was necessary.

Feeding by larvae and adults on the same host species

is an efficient strategy for any insect in utilizing a

host. Both stages can exert stress on the plant. Initial

ly, beetles feed on birch leaves to obtain energy necessary

for maturation and oviposition. This feeding can induce

the plant to allocate energy for the production and

mobilization of defensive phytochemicals. Adult beetles may avoid these toxic substances through "hopscotch" feed

ing. Indeed, in some years this allocation, as a result of

a feeding-induced defense response, may stress subtly or

approach a stress threshold level in the plant, and larvae may be more successful in these years.

After a maturation feeding period, female beetles oviposit in bark cracks and crevices, eggs mature and hatch, and larvae bore into subcortical tissues. The tree now has to use energy to defend itself against the borer stage. Depending again upon tree vitality, larvae may or may not be successful. 100

Birch trees may be assaulted continuously by adults

and larvae if an endemic beetle population is present.

Feeding by beetles, as adults and as larvae, causes trees

to allocate energy away from growth, reproduction, and/or storage towards defense and compartmentalization. Vitality thresholds probably determine the outcome of these alloca tions. At low vitality, defense and compartmentalization may not be priority tree functions. Host quality for adults begins to decrease, but for larvae, it begins to increase. As larval establishment becomes more successful, foliage quality deteriorates for adults. Defensive com pounds may not be as important to the adult as availability of nutrients. Adults begin to disperse to new hosts when foliage quality is no longer suitable.

The ecology of borer/host relationships is complex and warrants further investigation. This discussion suggests many avenues for research. How does a tree defend itself against foliage and subcortical herbivores? Is defense related to or dependent upon tree vitality? How can we measure this threshold? Does leaf quality become nutrient poor, thereby stimulating adult dispersal? What can be done to enhance tree vitality thereby increasing natural resistance to borer colonization? Basic information about tree and beetle physiology is needed to answer these questions. Significant Findings

1. B. pendula responds defensively to herbivory. Tree vitality may be extremely important in this response.

2. A. anxius reproductive biology is influenced by host species and environmental variables. Host quality must be considered when evaluating beetle biology.

3. Adult emergence can be predicted by accumulated heat units. For predicting 10% adult emergence, models using a base temperature of 8 ° C and a 1 May starting date for Columbus, and a base temperature of 10° C and 1 April starting date for Wooster were best.

4. Infested birch can be manipulated to expedite or delay beetle emergence. Felling date and bolt end treatments significantly influenced emergence density.

5. Larvae utilize both branches and tree trunks as food resources, but significantly less emergence occurs from branches and upper trunk. Collecting lower sections of recently killed birches will minimize time required to obtain large numbers of beetles for experimentation.

6 . Beetle mating behavior can be manipulated in the labora tory. Mating frequency did not influence fecundity but significantly more beetles 3- to 5-d-old mated than new ly emerged beetles. No close-range pheromonal com munication was observed.

101 Appendix A

Leaf Collection and Extraction

Leaf Collection

1. Remove 8 leaves/tree (2 leaves/quadrant)

2. Immediately submerge in liquid N2 .

3. Place in vial on dry ice.

4. Return to laboratory and freeze-dry.

5. Keep sample frozen until extraction.

Note Sample leaves same time of the day throughout the study.

Leaf Extraction

1. Use 5 ml of 70% acetone: 30% de-ionized water per 1 0 0 mg dry leaf tissue.

2. Extract leaf sample in a 40OC water for 24 hrs to boil-off acetone.

3. Add 5 ml of de-ionized water per 100 mg leaf tissue.

4. Centrifuge with tabletop centrifuge for 2- to 4- minutes until solids collect at bottom of tube.

5. Refrigerate samples until phytochemical analyses.

102 103

Appendix B

Determination of Total Phenols by Folin-Denis Method

Folin-Denis Reagent (FD)

1. To 750 ml H2 O, add 100 g sodium tungstate, 20 g phosphomolybdic acid, and 50 ml phosphoric acid.

2. Reflux 24 hrs in a soxhlet extractor, cool, dilute with de-ionized H2 O 1 :1 .

Phenolic Extraction

1. Add 0.1 ml leaf extract to 1 ml FD reagent.

2. Wait 3 min, add 1 ml 2N NaHC0 3 as a fixative.

3. Wait 60 min and determine spectrophometric absor bance at 725 nm against a blank of equal parts de ionized water, FD, and NaHCC^.

4. Construct a standard curve using tannic acid as a standard.

5. Determine total phenols in leaf extract in terms of tannic acid standard curve. 104

Appendix C

Determination of Hydrolysable Tannins by KIO4 Method

Hydrolysable Tannins Extraction

1. To 1.0 ml leaf extract, add 1.0 ml de-ionized water and 1.0 ml KIO4 (saturated KIO3 solution).

2. Place extract on ice for 40 min and determine spectrophometric absorbance at 550 nm against a blank of 2 ml de-ionized water and 1.0 ml KIO4 .

3. Construct a standard curve using tannic acid as a standard.

4. Determine hydrolysable tannins in leaf extract in terms of tannic acid standard curve. 105

Appendix D

Determiniation of Condensed Tannins by HC1 in BuOH Method

Condensed Tannins Extraction

1. Heat 0.5 ml leaf extract for 2 hrs at 95° C with 4.0 ml 5% conc. HC1 in n-BuOH and determine spectrophometric absorbance at 547 nm against a blank of 0.5 ml de-ionized water and 4.0 ml n-BuOH.

2. Construct a standard curve using quebraco acid as a standard.

3. Determine condensed tannins in leaf extract in terms of quebraco acid standard curve. 106

Appendix E

Determination of Tanning Coefficient by Protein Precipitate Method

Tanning Coefficient Extraction

1. Collect fresh steer blood and lyse immediately with cold (50 C) de-ionized water (1:1). Return to laboratory on ice and centrifuge to produce a cell membrane-free solution which remains stable 90 hrs at 50 c.

(I diluted hemaglobin solution further with 1 part blood:4 parts de-ionized water.)

2. Add 1.0 ml leaf extract, 1.0 ml de-ionized water, and 3.0 ml hemoglobin solution, vortex 15 sec, and centrifuge 7500 g's for 30 min. Decant supernatant and determine spectrophometric absorbance at 578 nm against a blank of 2.0 ml de-ionized water and 3.0 ml hemoglobin solution.

3. Construct a standard curve using tannic acid as a standard.

4. Determine tanning coefficient in leaf extract in terms of tannic acid standard curve. 107

Appendix P

Determination of Total Proteins by Bradford Method

Total Protein Extraction

1. Follow Bradford technique: dissolve 100 mg Coos- massie Brilliant Blue G-250 in 50 ml phosphoric acid; dilute final volume to 1.0 1. Refrigerated solution will keep for several weeks.

2. Add 5 ml Bradford reagent per 0.1 ml leaf extract, and vortex 5-10 sec.

3. Determine spectrophometric absorbance at 595 nm 2 min after vortexir.g but before 1 hr against a blank of 5 ml Bradford reagent and 0.1 ml de-ionized water.

4. Construct a standard curve using Albumin Bovine FR V powder (fatty acid poor) as a standard.

5. Determine total protins in leaf extract in terms of protein standard curve. LIST OF REFERENCES

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