Effect of sex-pheromone concentration on behavior of three strains of western spruce budworm male moths

The responses of male western spruce budworm moths,Choristoneura occidentalis Freeman, to a range of concentrations of the major sex pheromone, 928 (E/Z)-11-tetradecenal (Ald), in polyvinyl chloride lures, were observed using the electroantennogram technique, a flight tunnel, and field-trapping bioassays. The responses to virgin female moths were also observed in the flight tunnel and field bioassays. The moths were from three strains: a nondiapausing laboratory colony; field-collected wild budworm; and laboratory-wild crosses. The mean peak amplitude of antennal response and the time required for the electroantennogram signal to return to the baseline after stimulation (lag) increased with Ald concentration in both laboratory and wild moths. However, at Ald concentrations of 0.005% and greater, the lag period of the wild male's antennae was significantly shorter than that of the laboratory male's. The mean number of moths caught in the field in delta sticky traps increased with Ald concentration, but the number of moths caught per trap was not significantly different between concentrations of 0.005 % and 0.5 %. The threshold concentration required to elicit upwind flight in the flight tunnel was between 0.0005 and 0.005% Ald; peak response occurred to 0.05 % Ald but was not significantly different from that to 0.005 % or 0.5% Ald. Moths from all three populations significantly reduced their net upwind groundspeed as they approached the pheromone lure. When pheromone concentration was increased, the net upwind groundspeed of laboratory and lab-wild moths, but not wild moths, was significantly reduced between 2 m and 1 m downwind from the pheromone lure. The three populations of moths differed significantly in the percentage of wing-fanning and copulatory attempts, and in the net upwind groundspeed of flight from 2 m to 1 m downwind from the lure.     

Behavioral effects of secondary components of sex pheromone of western spruce budworm (Choristoneura occidentalis) free

In a laboratory wind tunnel, upwind flight and close-range orientation to a pheromone source by maleC. occidentalis were facilitated by the addition of the secondary componentsE/Z11-tetradecen-1-ol acetate (8911) andE/Z11-tetradecen-1-ol (8515) to low source concentrations of the primary components,E/Z11-tetradecenal (928). Male responses to the blends tested never equalled their responses to virgin females. The primary components alone, when released at a rate similar to that of a calling female, never elicited male upwind flight or source location. However, the addition of the secondary components enhanced these behavioral sequences.Lepidoptera: Tortricidae.     

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.     

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.     

Chemistry and field evaluation of the sex pheromone of western spruce budworm,Choristoneura occidentalis,Freeman

Chemical analyses and field bioassays showed a mixture of 92% (E)- and 8% (Z)-11-tetradecenal to be the sex attractant pheromone of the western spruce budworm,Choristoneura occidentalis Freeman. Females were also found to emit small amounts of the corresponding acetates and alcohols, but these components were not active in the bioassay. In contrast, in whole female tip extracts, (E)-11-tetradecenyl acetate predominates, and aldehyde pheromone components are present in lesser quantities, suggesting that final biosynthesis of pheromone takes place just prior to or during emission. At release rates approximating that of the female (2–4 ng/hr), a 928EZ blend of the synthetic aldehydes was at least as attractive as live females. Addition of the corresponding acetates or alcohols up to 50% of the aldehyde content did not significantly enhance or inhibit attraction. No major differences were apparent in pheromone production of females from a laboratory stock or from field collections from diverse geographic locations ranging from Colorado to British Columbia.     

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.     

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     

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.     

Behavior and survival of western spruce budworm,Choristoneura occidentalis Freeman,exposed to an ω-fluorinated pheromone analogue

-Fluorinated (E)-11-tetradecenal (14F-E11-14: Al) was synthesized using 1,10-decanediol as a starting compound. Male and female western spruce budworm,Choristoneura occidentalis Freeman, moths exposed to 14F-E11-14: Al had LC₅₀s (CI) of 12.0 (7.4–19.5) µg and 41.7 (22.7–76.2) µg, respectively. Antennectomized moths had lower mortality rates than normal moths. 14F-E11-14:Al elicited slightly lower amplitudes than 97:3 (E/Z)-11-tetradecenal (E/Z11-14:Al) in electroantennogram studies, but the lag or recovery period following excitation by 14F-E11-14:Al was much lower than forE/Z11-14:Al at the same concentrations. 14F-E11-14:Al andE11-14:Al evoked similar responses from male moths in wind-tunnel evaluations but neither compound was as effective as a virgin female in stimulating moths to fly upwind to contact the lure.     

Attraction ofCacoecimorpha pronubana male moths to synthetic sex pheromone blends in the wind tunnel

Attraction ofCacoecimorpha pronubana male moths to blends of four sex pheromone components was studied in the wind tunnel.Z11–14Ac alone did not elicit upwind flight, admixture of 10%Z11–14OH or more led to successful attraction of males to the source. Attractivity of these binary blends was further enhanced by addition ofE11–14Ac orZ9–14Ac; the optimum was a blend ofZ11–14Ac,Z11–14OH,E11–14Ac, andZ9–14Ac at the proportion of 1003033. In ternary and quaternary blends, the effect ofZ11–14OH andE11–14Ac was strongest at 30% and 3%, respectively. By contrast,Z9–14Ac increased behavioral responses over a wide range.     

Disruption of male spruce budworm orientation to calling females in a wind tunnel by synthetic pheromone

Male spruce budworm [Chorisloneura fumiferana (Clem.)] moths were held for 3 hr in a wind tunnel and subjected to various concentrations of background synthetic pheromone. They were then exposed to calling females and their response was recorded. The background pheromone was presented either as discrete turbulent plumes or as a uniform permeation throughout the tunnel. The numbers of males wing-fanning and flying in response to the calling females decreased as the concentration of background pheromone increased. Of the males which flew, a higher proportion progressed upwind in the discrete plumes than in the uniform permeation, an indication that structure in the pheromone cloud is necessary for upwind progression. In both discrete plumes and uniform permeation fewer males were able to locate the females (i.e., disruption was greater) as the concentration of synthetic pheromone increased, but for the same total release rates, disruption was greater when the synthetic pheromone was released in discrete plumes rather than in a uniform permeation. This implies that disruption which involves luring males to sources of synthetic pheromone is more effective than masking female plumes by uniform permeation and suggests that it is more efficient to release pheromone from a few potent sources than from numerous low-potency sources.     

The role of monoterpenes in resistance of Douglas fir to western spruce budworm defoliation

We conducted defoliation experiments with 7- to 8-year-old clones of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco var. glauca] to assess the role of monoterpenes as a resistance mechanism to western spruce budworm (Choristoneura occidentalis Freeman) defoliation. The grafted clones were derived from mature trees that showed resistance or susceptibility to budworm defoliation in the forest. All clones were exposed to either budworm defoliation or nondefoliation treatments in 1998 and 1999 under greenhouse conditions. We found that the total concentration of monoterpenes in current-year foliage varied greatly between two consecutive years in clones in the greenhouse and in their corresponding mature trees in the forest. Fractional composition of different monoterpenes was similar between different years and between clones and mature trees, indicating genetic control of this trait. Two different defoliation experiments were conducted to assess the importance of budburst phenology as a factor determining host plant resistance. In the 1998 experiment, budworm feeding was matched to the budburst of each individual plant. Monoterpene concentration was high in 1998, and budworm potential fitness was greater on clones from the resistant mature trees that had lower concentrations of total monoterpenes. In the 1999 experiment, budworm feeding was matched to budburst of the whole population of plants in order to mimic conditions similar to insects feeding on trees in the field. The concentration of monoterpenes was low in 1999, and budworm fitness was not related to monoterpenes. Total monoterpene concentration was negatively related to foliar nitrogen concentration, suggesting that C/N balance may affect monoterpene synthesis in needles. However, tree growth was not related to total monoterpene concentration. We concluded that expression of differences in budworm resistance among Douglas fir genotypes might be caused by interactions among multiple resistance mechanisms such as needle monoterpenes and tree budburst phenology.     

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.     

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.     

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.     

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.     

Identification of sex pheromone components of jack pine budworm,Choristoneura pinus pinus freeman

Chemical identification and field-trapping experiments have shown that a blend of 8515 (E,Z)-11-tetradecenyl acetates and 8515 (E,Z)-11-tetradecen-1-ols (in a 91 ratio) are female sex pheromone components for jack pine budworm,Choristoneura pinus pinus. This blend of chemicals, formulated in PVC (0.1 %, w/w) sources is as effective a trap bait as virgin females. Preliminary wind tunnel observations have indicated that this blend, effective as a trap bait, is not equivalent to females.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.     

Pattern of pheromone-oriented flight in male potato tuberworm moths

The pheromone-oriented flight of maleP. operculella was observed under field conditions. Eighty percent or more of the flights were shorter than 1 m. Thus the approach of males of this species to a distant pheromone source is composed of a chain of short flights. The pattern of the flights changed when the males came within about 1 m of the lure, with a decrease of flight speed and an increased tortuosity. This probably facilitates eventual location of the female by a male. Only a few males succeeded in arriving at the high-dose lures. Males did not succeed in arriving at the lure when it was 70 cm above the ground: this was confirmed by a trap test; however, the flight pattern consisted of a chain of short flights even in these cases. The adaptive significance of this flight pattern is discussed.     

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.