Female Budworm Research Articles

Mass Trapping Lepidopteran Pests with Light Traps, with Focus on Tortricid Forest Pests: What If?

The management of Lepidopteran pests with light traps (LTs) is often achieved by luring adults to death at light sources (light trap-based mass trapping, or LTmt). Large-scale LTmt programs against agricultural pests initiated in the late 1920s in the United States were phased out in the 1970s, coinciding with the rise of pheromone-based management research. The interest in LTmt has surged in recent years with the advent of light emitting diodes, solar power sources, and intelligent design. The first step in implementing LTmt is to identify a trapping design that maximizes the capture of target pests and minimizes the capture of non-target beneficial insects-with a cautionary note that high captures in LTs are not equivalent to the feasibility of mass trapping: the ultimate objective of LTmt is to protect crop plants from pest damage, not to trap adults. The captures of egg-carrying females in light traps have a greater impact on the efficiency of LTmt than the captures of males. When LTmt is defined as a harvesting procedure, the biomass of females in LTs may be viewed as the best estimator of the mass trapping yield; biomass proxy has universal application in LTmt as every living organism can be defined on a per weight basis. While research has largely focused on agricultural pests, an attempt is made here to conceptualize LTmt as a pest management strategy in forest ecosystems, using spruce budworm as a case study. The mass trapping of female budworms is impossible to achieve in endemic populations due to the large spatial scale of forest landscapes (implying the deployment of a prohibitively large number of LTs); in addition, ovipositing female budworms do not respond to light sources at a low density of conspecifics. The light-based mass trapping of female budworms may provide a realistic management option for geographically isolated forest stands heavily infested with budworms, as a tool to prevent tree mortality. Somehow unexpectedly, however, one factor obscuring the feasibility of LTmt is as follows: the complex ('unknowable') economic valuation of forest stands as opposed to agricultural landscapes.

Polyandry across Behavioral Classes in Female Spruce Budworm

Reproduction in spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), is characterized by sedentary oviposition in the natal forest patch early in life (gravid females are incapable of flight due to their heavy abdomen) followed by windborne migrations among females that have laid >50% of their eggs; the nature of migrations (facultative or obligatory) remains unknown. The incidence of polyandry (females with more than one spermatophore in their reproductive tract) was evaluated for several thousand field-collected female budworms (data professionally archived at Canadian Forest Service) using an array of sampling procedures that can be delineated along four behavioral classes: (1) resident females collected on host trees; (2) in-flight females captured while foraging in forest canopies; (3) migrant females captured above tree canopies; and (4) females collected postmortem on drop trays. Overall, polyandry increased over time (reflecting the ageing of local populations) and with female body size (likely due to male mating preference for large, most fecund females). Polyandry did not increase postmortem realized fecundity of females. The level of polyandry was lowest among migrants, intermediate for in-flight and resident females, and highest for naturally dead females. Sedentary reproduction among young female budworms may limit gene flow and increase the risk of inbreeding; a low level of polyandry among migrants may thus be due to females not only seeking novel habitats for their progeny but also mating partners that are not closely related genetically.

Size-Dependent Realized Fecundity in Two Lepidopteran Capital Breeders.

Body size is correlated with potential fecundity in capital breeders, but size-dependent functions of realized fecundity may be impacted by reproductive losses due to mating failure or oviposition time limitations (number of eggs remaining in the abdomen of females at death). Post-mortem assessment of adults collected in the field after natural death represents a sound approach to quantify how body size affects realized fecundity. This approach is used here for two Lepidoptera for which replicated field data are available, the spruce budworm Choristoneura fumiferana Clemens (Tortricidae) and bagworm Metisa plana Walker (Psychidae). Dead female budworms were collected on drop trays placed beneath tree canopies at four locations. Most females had mated during their lifetime (presence of a spermatophore in spermatheca), and body size did not influence mating failure. Oviposition time limitation was the major factor restricting realized fecundity of females, and its incidence was independent of body size at three of the four locations. Both realized and potential fecundity of female budworms increased linearly with body size. Female bagworms are neotenous and reproduce within a bag; hence, parameters related to realized fecundity are unusually tractable. For each of five consecutive generations of bagworms, mating probability increased with body size, so that virgin-dead females were predominantly small, least fecund individuals. The implication of size-dependent reproductive losses are compared for the two organisms in terms of life history theory and population dynamics, with an emphasis on how differential female motility affects the evolutionary and ecological consequences of size-dependent realized fecundity.

Oviposition strategies employed by the western spruce budworm: tests of predictions from the phylogenetic constraints hypothesis

Abstract1 Predictions from the Phylogenetic Constraints Hypothesis were tested for the first time in an eruptive forest Lepidopteran species, the western spruce budworm.2 In previous work, we established that western spruce budworm females exhibit oviposition preferences with regard to tree age, tree vigour and host species. However, there was no evidence to support a link between oviposition preference and larval performance, which supports the Phylogenetic Constraints Hypothesis.3 Our preference data led us to test whether female budworms use oviposition strategies to select the sites where they lay their egg masses. Our experiments were designed to make direct comparisons between latent and eruptive insect herbivores with respect to two oviposition behaviours: egg retention and avoidance of conspecifics. This type of research has not previously been conducted on any eruptive forest Lepidopteran.4 Female budworms retained eggs instead of laying them on less preferred hosts in two of three experiments, but the percentage of eggs they retained was significantly less compared to latent insect herbivores.5 In addition, female budworms actively avoided oviposition in areas with the highest density of conspecific egg masses, but they laid egg masses in all the other locations provided. This contrasts with the pattern seen in latent insect herbivores, which consistently avoid laying their eggs near any sites already used by conspecifics.6 Our research indicates that there are extreme differences between latent and eruptive insect herbivores with respect to egg retention and avoidance of conspecifics, thus supporting the Phylogenetic Constraints Hypothesis.

A BIOLOGICALLY ACTIVE ANALOGUE OF THE PRIMARY SEX-PHEROMONE COMPONENTS OF SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

Disruption of mating and of trap capture of spruce budworm, Choristoneura fumiferana (Clem.), has been accomplished in recent years (reviewed in Silk and Kuenen 1984) by disseminating large quantities of the primary components (synthetic) of the female sex pheromone within a forest environment. These components (E)- and (2)-11-tetradecenal (E/Z11-14:Ald) (Sanders and Weatherston 1976) are emitted by virgin female budworm at a 95/5 E/Z ratio (Silk et al. 1980). Unsaturated aldehydes are expensive, tend to polymerize readily (Dunkelblum et al. 1984), and are susceptible to air oxidation and/or photodegradation in the field environment. Analogues, with increased stability and reduced cost, that duplicate the effects of these pheromone components would therefore be of practical value.

Effect of Sex and Instar on Food Consumption, Nutritional Indices, and Foliage Wasting by the Western Spruce Budworm, Choristoneura occidentalis

Consumption rates, food utilization efficiencies, and foliage wasted by the western spruce budworm, Choristoneura occidentalis , were determined for three larval instars and for both sexes. Sixth-instar larvae ingested significantly more Douglas-fir foliage than did fifth-instar larvae. Relative consumption rate ( RCR ), relative growth rate ( RGR ), efficiency of conversion of ingested foods ( ECI ), and the percentage of foliage wasted were statistically equal (α = 0.10) between fifth- and sixth-instar larvae feeding on host foliage. Fourth-instar larvae feeding on artifical diet medium ingested less food than did fifth- and sixth-instar larvae. Relative growth rate was greater for fourth- and fifth-instar larvae, ECI was greater for fifth- and sixth-instar larvae, and RCR was greater for fourth-instar larvae. Female budworms consumed less host foliage in relation to their body weight than did males. However, females maintained an RGR equal to that of males due to greater ECI. Female budworms had significantly longer development times and greater fresh pupal weights than males. The percentages of total damaged host foliage that was wasted by male and female western spruce budworms were statistically equal. The percentages of foliage wasted were also statistically equal for fifth- and sixth-instar larvae feeding on Douglas-fir foliage.

Douglas-fir (Pseudotsuga menziesii)-spruce budworm (Choristoneura occidentalis) interactions: the effect of nutrition, chemical defenses, tissue phenology, and tree physical parameters on budworm success.

Measurements of foliage quality, physiological, and phenological condition of sample trees were used as independent variables in multiple correlation analyses to determine their effect on female and male spruce budworm larval dry weights. Female budworm from trees high in foliar concentrations of beta-pinene, myrcene and total nitrogen weighed less than those from trees lacking these characteristics. Male budworm from trees high in foliar concentrations of alpha-pinene, myrcene, terpinolene, citronellyl acetate, and bornyl acetate weighted less than those from trees lacking these characteristics. Additionally, relatively vigorous and productive trees tended to be less susceptible (as evidenced by reduced larval weight) to budworm of either sex.

TESTS OF MOTOR STIMULANTS FOR EASTERN SPRUCE BUDWORM MOTHS (LEPIDOPTERA: TORTRICIDAE)

AbstractThe insecticide phosphamidon, both alone and mixed with other chemicals, was tested in the laboratory as a motor stimulant to female spruce budworm moths. For phosphamidon alone, the time to reaction of virgin female budworm (Choristoneura fumiferana) moths was about 40 min. However, small supplements of pyrethrum or synthetic pyrethroids reduced the reaction time to about 3–8 min. The slow reaction to phosphamidon alone could account for the failure of that insecticide to kill gravid females. It is postulated that moths quickly stimulated to flight activity within the canopy would be more likely to acquire a lethal dose of insecticide before the spray cloud dissipated.

FACTORS AFFECTING ADULT EMERGENCE AND MATING BEHAVIOR OF THE EASTERN SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

AbstractLaboratory and field experiments indicate that the female spruce budworm (Choristoneura fumiferana (Clem.)) pupal stadium requires approximately 122C degree-days above a threshold of 7.2 °C (45°F), the male 124. Emergence time on any given day depends on temperature but is independent of photoperiod. Under field conditions male and female budworm mate only once per 24-h period. In the laboratory under continuous illumination females mate repeatedly and males readily mate a second time within a few hours, but the duration of the second copulation is abnormally long. The probability of multiple matings under field conditions is reduced by the restricted period of sexual activity coupled with the duration of copulation and the lower competitiveness of mated insects. Antennae are essential to the male for successful copulation.

Development of the Black-Headed Budworm in the Laboratory1

Two successive generations of Acleris variana (Fernald) were successfully reared in the laboratory on both western hemlock and Sitka spruce foliage. There was no difference in development time (egg to adult) between 1st generation bud worms reared at an average temperature of 66°F (range 58–71° and 2nd generation budworms reared at 71°F (range 69–72°. The average development time of budworms (egg to adult) was approximately equal when reared on hemlock and spruce. Female budworms had a longer life span (88 days) than males (77 days) when reared on either hemlock or spruce. This difference in life span was greatest in the adult stage.