Tests for induction of feeding preferences in larvae of eastern spruce budworm using extracts from three host plants

Feeding preferences to extracts from three host plants were determined for sixth-instar eastern spruce budworm larvae reared on one of three hosts or on artificial diet. Preferences of foliage-reared larvae were compared to those of diet-reared, or naive, larvae. No effect of plant induction was found using amino acids and bases and chloroform extracts on test disks in three-choice experiments. Possible effects of habituation for sugars and glycosides from white spruce were shown. Organic acids contributed to a phenomenon of avoidance learning in larvae reared on all three hosts, showing that this fraction from balsam fir was the least deterrent, while that from black spruce was the most deterrent.     

Metabolism of pheromone components and analogs by cuticular enzymes ofChoristoneura fumiferana

In vivo incubation ofChoristoneura fumiferana with (E)-11-tetradecenal, the major pheromone component, resulted in adsorption followed by transformation to (E)-11-tetradecenoic acid, the only observed metabolite. Antennae, legs, and wings from both sexes were investigated for enzyme activity. Specificity studies with the aldehyde dehydrogenase system showed that the enzyme prefers aldehydes of 14-carbon chain length or shorter.     

Feeding responses of eastern spruce budworm larvae to sucrose and other carbohydrates

Spruce budworm larvae reared on an artificial diet were tested for preference of twelve carbohydrates over a water control. A strong preference for sucrose was seen, followed by fructose, inositol, and glucose. Male and female larvae do not differ in their responses to sucrose. The behavioral threshold for sucrose is at 10^–4 to 10^–3 M, with a peak response in the range of 0.01 to 0.05 M sucrose. Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae).Work leading to this publication was funded in part by a USDA Forest Service sponsored program entitled Canada/United States Spruce Budworms Program (grant 23–352), and in part by the National Sciences and Engineering Council of Canada (operating grant A9723), and in part by the Whitehall Foundation.     

Repellency of oral exudate to eastern and western spruce budworm larvae (Lepidoptera: Tortricidae)

A two-choice feeding bioassay was used to investigate the intra-specific repellency of the larval oral exudate of eastern and western spruce budworms,Choristoneura fumiferana (Clem.) andC. occidentalis Free., respectively. Results of the bioassay indicated that feeding behavior on artificial diet-drop feeding stations was modified in the presence of exudate, with feeding stations treated with conspecific exudate being avoided when an untreated station was available 3 cm away. Feeding was suppressed when a single, exudate-treated station was provided, or when the treated and untreated stations were separated by only 1 cm. The repellent effect functioned both inter- and intraspecifically. When induced to produce exudate,C. occidentalis larvae were not immediately repelled by either their own or other individuals' exudate. However, 24 hr after induction, test larvae were repelled by exudate from either source. In both species, larval oral exudate probably functions to repel conspecific competitors.     

Sex pheromone chemistry of the western spruce budwormChoristoneura occidentalis Free

SCOT capillary Chromatographic and SCOT capillary chromatographic-mass spectrometic analyses of gland washes and effluvia of virgin femaleChoristoneura occidentalis Free, have been conducted with both a diapausing and nondiapausing strain of this insect. The following compounds were identified in gland washes and effluvia in both strains:E andZ11–14Ald,E andZ11–14Ac,E andZ11–14OH and 14Ald, 14Ac, and 14OH. The average aldehyde: acetate: alcohol ratio found by analysis of single glands by virgin females (nondiapausing strain) was 170.73. Analysis of virgin female effluvia gave this ratio as 1038 (diapausing strain: %Z=8, 11, 15, respectively) and 1036 (nondiapausing strain: %Z=8, 11, 12, respectively). The saturated components were generally 1–2% of theE isomer in each case. Comparisons of EAG responses of bothC. occidentalis andC. fumiferana toE11–14Ald,E11–14Ac andE11–14OH were made. Correlations with both laboratory and field data previously published were also made betweenC. fumiferana andC. occidentalis.Lepidoptera: Tortricidae.     

Effect of a Rugulosin-producing Endophyte in Picea glauca on Choristoneura fumiferana

Disease-free second instar Choristoneura fumiferana (eastern spruce budworm) were placed on trees infected with a rugulosin-producing needle endophyte in two experiments. They were allowed to grow to sixth instar when survivors were collected. First, by using 3-yr old trees, a comparison was made of budworm growth on infected and uninfected trees. A second experiment used 4-yr old trees to study the effect of rugulosin content in the needle on growth. This permitted an examination of a dose response in relation to growth, and allowed us to eliminate the potential for differences in environment or foliar chemistry affecting the results. At sixth instar, budworms feeding on infected trees that contained rugulosin were smaller than those on uninfected trees. At needle concentrations above the dietary low observed effect level of rugulosin for C. fumerana >0.5 μg g⁻¹, a dose response was seen. For the first time, this demonstrates an inverse effect in outdoor nursery experiments between budworm weight and rugulosin concentration.     

Differences in oxidase and esterase activities involved in pheromone biosynthesis in two species ofChoristoneura

The released pheromone and the glandular lipids, labeled with [¹⁴C]acetate, were analyzed fromChoristoneura orae andChoristoneura fumiferana budworm moths by thin-layer chromatography and autoradiography. Radiolabeled lipids in the gland appeared to be identical in the two moths with both insects containing high amounts of 11-tetradecenyl acetates. In contrast, theC. orae moths released primarily labeled acetate ester and alcohol, and the spruce budworm moths (C. fumiferana) labeled aldehyde consistent with the known composition of their respective pheromones. The levels of the enzymes responsible for converting the acetate ester into aldehyde were found to be significantly lower in gland extracts fromC. orae moths than fromC. fumiferana moths. These results implicate an acetate esterase and an alcohol oxidase in controlling the composition of the pheromone blend released from closely related budworm species.     

Development of a bioluminescence assay for aldehyde pheromones of insects

A newly developed bioluminescent assay was used to measure quantitatively the amount of (E)-11-tetradecenal, the major component of the sex pheromone of the spruce budworm, trapped on Porapak Q^®. The bioluminescent response was linearly related to the amount of aldehyde either deposited on the absorbent or trapped from an airstream. However, the recovery of pheromone from Porapak was dependent on whether the air was prefiltered (through Porapak) or taken directly from the atmosphere. Furthermore, pheromone on Porapak was lost with time during the flow of air through the absorbent, indicating that trapping of aldehyde pheromone should be conducted for short periods of time for optimal recoveries. The applicability of the assay system for the rapid and direct measurement of the release rates of aldehyde pheromone lures was demonstrated for pheromone lures used for baiting spruce budworm traps.This investigation was supported by the U.S.D.A. Forest Service Program entitled Canada United States Spruce Budworms Program (23–345) and the Medical Research Council of Canada (MT-4314).     

Behavioral responses of the female eastern spruce budwormChoristoneura fumiferana (Lepidoptera,Tortricidae) to the sex pheromone of her own species

Female eastern spruce budworm moths respond to the synthetic sex pheromone of their own species (a mixture ofcis- andtrans-11-tetradecenal) by walking, antennal grooming, flexation of the body, extension of the ovipositors, and oviposition. The sex pheromone is perceived by receptors on the antennae. Electroantennogram responses from the female are approximately two-thirds the amplitude of those obtained from males.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Insect olfactory receptor responses to components of pheromone blends

Multicomponent pheromone systems are common in many insect species. As our knowledge about the number of different chemical compounds actually involved in a particular communication system increases, so too does the need for an efficient neural mechanism for the encoding of behaviorially relevant odor compounds. Here we consider the electrical activity of olfactory receptor neurons in a subset of the individual pheromone-sensitive sensilla on the antennae of male cabbage looper moths (Trichoplupia ni). Responses to single- and multiple-component stimuli, drawn from seven behaviorally active compounds, were obtained at several different intensities. Some blends elicited electrical responses which were not readily predicted from a knowledge of the receptor neuron's response to individual components.     

Kairomone-mediated host finding by spruce budworm egg parasite,Trichogramma minutum

The host-finding responses of the egg parasite,Trichogramma minutum Riley, reared from its natural host,Choristoneura fumiferana (Clemens) and a laboratory host,Sitotroga cerealella (Oliver), to hexane extracts of scales of these hosts were compared in laboratory experiments. When presented withC. fumiferana eggs on filter papers treated with hexane and hexane extract of grain moth scales, egg finding byT. minutum was random. When presented with budworm eggs on filter papers treated with hexane and hexane extract of budworm scales,T. minutum found significantly more eggs on extract-treated filter papers, indicating the presence of kairomones on the scales of spruce budworms.T. minutum responded to kairomone-treated patches with a localized search behavior characterized by intense antennal tapping, decreased locomotion and increased turning within the patch, and repeated returns to the patch. In the absence of successful host finding, this response slowly waned. No significant difference in behavior ofT. minutum reared on eitherC. fumiferana orS. cerealella was observed.     

Flight and copulation of female spruce budworm in pheromone-permeated air

High concentrations of synthetic sex pheromone caused increased flight activity among mated female spruce budworm of all ages, a fact that may indicate an increase in dispersal. Flight activity also increased among older virgin females, but not among females one day old, the age at which they usually mate. Receptivity of young virgin females to courting males was not affected by pheromone-permeated air. Synthetic sex pheromone is therefore not likely to influence mating frequency through its effects on female activity.     

Attraction of male spruce budworm moths,Choristoneura fumiferana (Clemens), to pheromone-baited traps in small-tree thinnings

Mean catches of spruce budworm,Choristoneura fumiferana (Clemens), moths were not significantly different among four small-tree thinning treatments of young spruce-fir-hemlock regeneration. Significant inverse relationships were found between trap catches and distances to nearby spruce-fir-hemlock overstory. Prevailing wind directions indicated that moths were attracted anemotactically to upwind pheromone sources. No definite trends were detected between catches and temperature or precipitation.Lepidoptera: Tortricidae.A contribution to the Canada/ United States (CANUSA) Spruce Budworms Program. Mention of proprietary products does not constitute an endorsement of those products by the USDA.     

Enniatins fromFusarium avenaceum isolated from balsam fir foliage and their toxicity to spruce budworm larvae,Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae)

Material extracted from hyphae ofFusarium avenaceum, isolated from foliage of balsam fir,Abies balsamea, was toxic to spruce budworm larvae when incorporated into insect diet. The major insecticidal component of the toxic fraction was identified by chemical and spectroscopic methods as enniatin complex, rich in enniatin A/A₁. Possible ecological implications of these observations are considered.     

Synthesis of pungenin,a foliar constituent of some spruce species,and investigation of its efficacy as a feeding deterrent for spruce budworm [Choristoneura fumiferana (Clem.)]

Pungenin was synthesized from 3,4-dihydroxyacetophenone by a short sequence involving manipulation of protecting groups on the 3 and 4 hydroxyl functions. Bioassays indicated that the glucoside is a modest feeding deterrent for sixth-instar spruce budworm larvae, but it does not appear to retard the development of small larvae or lead to increased mortality.     

Feeding preferences of eastern spruce budworm larvae in two-choice tests with extracts of mature foliage and with pure amino acids

The feeding preferences and feeding rates of eastern spruce budworm on extracts from mature foliage normally avoided by larvae indicate that the chemical composition of four major host plants does not account for this avoidance. Other factors such as the degree of lignification and/or moisture content of the older foliage may play a more important role. Of 14 amino acids tested, alanine, lysine, proline, and serine stimulated feeding. The interactions of amino acids and sucrose were studied, and the results are discussed in relation to feeding preferences and feeding rates.     

Orientation behavior of second-instar larvae of eastern spruce budwormChoristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae) in a y-type olfactometer

A two-choice, wind-tunnel olfactometer was designed and contructed to determine whether second-instar eastern spruce budworm larvae,Christoneura fumiferana (Clem.), could detect and discriminate among host-plant volatiles. Volatiles of current year's growth ofPicea glauca were preferred over those ofP. rubens, P. mariana, or air.Abies balsamea was preferred overP. mariana or air.P. rubens andP. mariana were both preferred over air. Two-year-old growth ofP. glauca, A. balsamea, P. rubens, andP. mariana were all preferred over air. Current year's growth of these host evergreen species was usually preferred over former year's growth of the same species in each case.     

Spruce budworm (Choristoneura fumiferana) pheromone chemistry and behavioral responses to pheromone components and analogs

This paper reviews the sex pheromone chemistry and pheromone-mediated behavior of the spruce budworm and related coniferophagous (Choristoneura) budworms. InC. fumiferana, temporal changes in pheromone-gland monounsaturated fatty acids (pheromone precursors) enable the prediction of the primary sex pheromone components. This technique may also be applicable for predicting additional pheromone components. Tetradecanal (14 Ald), previously shown to enhance close-range precopulatory behavior, lowers the threshold of response by males for upwind flight to a pheromone-component source. Spruce budworm males maintain upwind flight to 955 (E/Z)-1,12-pentadecadiene (diolefin analog) after initiating upwind flight to a primary-component pheromone source (955E/Z11-14Ald). This is the first demonstration of apparently normal male flight responses to a pheromone analog.Lepidoptera: Tortricidae     

Olfactory response of eastern spruce budworm larvae to red spruce needles exposed to acid rain and elevated levels of ozone

Second-instar eastern spruce budworm larvae,Choristoneura fumiferana (Clem.), were tested in a two-choice, Y-type, wind-tunnel olfactometer for preferences for red spruce,Picea rubens Sarg., needles exposed for eight weeks to charcoal-filtered air (CFA) or 0.15 ppm ozone (O₃) in combination with acidified rainfall at pH 4.2 or 3.0. Volatiles from needles treated with CFA plus pH 4.2 rain (control) were preferred over those from needles exposed to pH 3.0 rain + O₃ or O₃ alone; O₃-treated needles were chosen over those exposed to pH 3.0 rain + O₃. No preference was shown between the pH 4.2 and 3.0 rain treatments. Larvae chose purified air flowing through the olfactometer in preference to needle volatiles from the pH 3.0 rain + O₃ treatment.The use of trade, firm, or corporation names in this paper is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Forest Service of any product or service to the exclusion of others that may be suitable.