Populations of western blackheaded budworm, Acleris gloverana (Walsingham), have fluctuated widely over the length of Vancouver Island with five outbreaks having occurred since 1941. The core of the severe defoliation occurred in the southern and northern portions of a central mountain chain running the length of the Island. Four monitoring sites were established in the central core area and five in peripheral sites during the 1970-1973 outbreak. At each site, samples were taken during five different life stages per generation, beginning at the peak of defoliation and ending when larval densities declined below detectable levels. The largest losses during the population collapse occurred during the larval period when large numbers abandoned the damaged trees by spinning off on silk threads. In addition, when age-specific survival ratios for each developmental stage were compared with the generation survival ratio, the closest relationship occurred between generation survival and the adult dispersal and oviposition period. Large emigration away from the central core area of defoliation to peripheral stands was detected, particularly during the first year of collapse. We suggest that, in response to damaged foliage, larvae and adults disperse from the stands and the outbreak collapses before the trees are killed. The dispersal response of defoliating populations appears to dampen the upward population trend. The trees survive, refoliate, and thus preserve the habitat for potential population increases during the next outbreak period. Host interrelationships during population gradations of the blackheaded budworm are compared with other conifer defoliators of British Columbia, particularly the western spruce budworm and the Douglas-fir tussock moth.

(E)-11,13-Tetradecadienal (E11,13-14:Ald) is the major component of the sex pheromone of the western blackheaded budworm (WEB), Acleris gloverana Walsingham. The compound was identified in extracts of the female's pheromone gland by coupled gas chromatographic - electroantennographic detection (GC-EAD) and coupled GC - mass spectrometry in selected ion monitoring mode. In field experiments, E11,13-14:Ald by itself was attractive, but addition of (Z)-11,13-tetradecadienal doubled trap catches of male WEB. (E)-11,13-Tetradecadienol or (E)-11,13-tetradecadienyl acetate in binary or ternary combination with E11,13-14:Ald did not enhance attractiveness of the bait. In comparative assessments of five different trap designs, Uni-traps appeared to be the most suitable for use in pheromone-based monitoring of populations of WEB.

Male moths of Choristoneura occidentalis Freeman, C. biennis Freeman, C. fumiferana (Clemens), and C. orae Freeman were caught in pheromone-baited traps. Ten traps were placed at each site, five baited with an aldehyde lure and five with an acetate lure. This procedure permitted separation of species based on the specific chemical lure and also provided specimens for further study of morphological and isozyme differences. The color of the forewings, presence or absence of spicules on the aedeagus, and a specific allozyme frequency were determined on selected specimens where these characteristics were useful in separating species at a particular site. Distributions of all species were more extensive than previously known, sometimes adding hundreds of kilometres to the recorded range. Areas of sympatry were identified and the fidelity and usefulness of characteristics for separating species in areas of overlap were discussed.

Adults of Choristoneura fumiferana, C. biennis, and an unidentified species reared from larvae or caught in pheromone traps from British Columbia were used for isozyme analysis to confirm the species identity, and for morphological study to determine the percentage of individuals with spiculate aedeagi. About 82% of C. fumiferana and less than 3% of both C, biennis and C. unidentified species (CPG) have spicules on the left side of their aedeagi. The number of moths that need to be sampled to determine a species is presented, based on the presence or absence of spicules.

In a synthesis of outbreak characteristics of common defoliating insects in British Columbia, two types emerge: those with fast-cycling outbreaks and those with sustained outbreaks. Species with fast-cycling outbreaks rise quickly to visible defoliation levels, cause significant growth loss, tree deformation and mortality, and disappear just as quickly. Impact is closely related to the severity of defoliation during the first year of an outbreak; consequently, the objective of managing these species should be to reduce populations before defoliation occurs, i.e. to prevent the outbreak. To accomplish this objective, identification of susceptible habitats and monitoring with sensitive pheromone traps in areas of expected outbreaks are necessary to detect upwelling populations. Species with sustained outbreaks cause significant growth losses only after defoliation continues for a number of years. Tree mortality usually is not important except where regeneration is being nurtured under a selective or shelterwood silvicultural system. Impact can be significant over the life of a stand because of the length and frequency of outbreaks, but treatments effective for only 1 year usually cannot be justified except where it is important to retain a full crown. Long-term cultural methods appear to be the preferred management system and, of these, utilizing nonhost species or resistant or phenologically asynchronous host species may be the best option. Again, determining the location of expected outbreaks is an important component of a management system and, at present, identifying stands by frequency of outbreak within zones of climatic suitability would be useful in selecting treatment areas.

3,13-Dimethylheptadecane (3,13-dime-17Hy) is the major sex pheromone component of the western false hemlock looper (WFHL),Nepytia freemani Munroe. It was identified in extracts of female pheromone glands by coupled gas chromatographic-electroantennographic detection (GC-EAD) and coupled GC-mass spectroscopy (GC-MS). Traps baited with 100μg of 3,13-dime-17Hy attracted large numbers of male WFHL. Of five additional candidate pheromone dimethylated hydrocarbons, only 3,13-dimethylhexadecane attracted male WFHL. However, neither 3,13-dime-16Hy nor the other four compounds enhanced attraction to 3,13-dime-17Hy when tested in binary or ternary combination at respective ratios of 100∶10, 100∶1, or 100∶1∶1. Identification of the complete WFHL sex pheromone requires structural elucidation of all 12 EAD-active components in gland extracts, determination of their chirality, and field testing of antennally active isomers in appropriate combinations and ratios. Stereoisomeric 3,13-dime-17Hy as trap bait may already be used to monitor WFHL populations.

Growth and survival of seedlings were determined for 1 to 3 years following defoliation by black army cutworm, Actebiafennica (Tausch.). Ten data sets were collected on three sites and included four species of seedlings: interior Douglas-fir, Pseudotsugamenziesii var. glauca (Beissn.) Franco; lodgepole pine, Pinuscontorta Dougl.; western larch, Larixoccidentalis Nutt.; and Engelmann spruce, Piceaengelmannii Parry. Mortality following defoliation cannot be assessed until after the flush in the next growing season because completely defoliated seedlings often regenerate new foliage and survive. More than 90% of the total mortality that did occur was detected at that time. Mortality of up to 39% occurred when seedlings were defoliated more than 60%; most of this occurred when planting was carried out concurrent with defoliation. Synergistic root stress effects caused by poor planting, dry sites, or drought significantly increased mortality. Height growth was significantly reduced when defoliation was greater than 60%; the greatest effects occurred when terminal bud destruction accompanied needle loss. Growth losses were greatest the year of defoliation; recovery of height growth of lodgepole pine was complete by the 2nd year on good growing sites. On poor sites, retardation of lodgepole pine height growth was still evident after 3 years.

Individual larvae of western spruce budworm (Choristoneura occidentalis Freeman) were observed from overwintering emergence to pupation at six locations spread over a wide range of altitudes and thus climate. A weekly census of 100 lower-crown buds per plot indicated large differences in rates of bud development and larval survival among locations.Emerging second-instar larvae attempted to mine swelling buds of Douglas-fir. If the buds were hard and tight, larvae mined 1-year-old needles until penetrable buds were available. Larvae dispersed over the crowns with only one larva becoming established in each bud; thus, many early-emerging and surplus larvae could not find suitable feeding sites and disappeared. Within the protective bud, survival was high. After buds flushed and larvae became exposed, densities dropped, probably due to increased predation and decreased food quality. Correlations indicated a close association between larval survival for the exposed period between bud flush and pupation, and overall larval survival.Douglas-fir trees responded to initial bud removal, but not to needle removal, by inducing latent buds in the axils of needles to grow into active vegetative buds ready to develop and flush the next spring. The number of these new vegetative buds formed was greatest when the initial buds were removed early in the season before flush, and decreased thereafter. Trees with vigorous crowns had the greatest response to defoliation by inducing the largest number of latent buds into becoming active vegetative buds; these were found mainly on the 2- and 3-year-old internodes.

A naturally occurring virus often leads to the development of an epizootic late in the outbreak cycle of the Douglas-fir tussock moth, but not before significant damage occurs to the trees. This virulent virus can be mass-produced in the laboratory and, when applied early in the outbreak cycle, can prevent severe defoliation. This, however, requires that an early-warning system be integrated with a virus treatment. The development and integration of a pheromone monitoring system with a virus treatment is described. Stands susceptible to Douglas-fir tussock-moth outbreaks are defined by overlying maps of past outbreaks, forest and habitat types, and climatic zones. Pheromone-baited traps are placed and monitored annually at permanent locations in the susceptible areas. Measuring annual trends of moth density indicates the time and location of the next outbreak. Trap-catch data provide an early warning of impending outbreaks. This is confirmed by ground reconnaissance. Insect density and defoliation is predicted from egg-mass and larval sampling. The virus then can be applied from the air or from the ground into threatened stands to initiate an epizootic to prevent the development of an outbreak and to minimize tree damage. The virus appears to spread, and field tests with reduced dosages indicate that that small amount of virus applied can still decimate larval populations and prevent tree mortality, at considerably reduced cost.

Catch rates of black army cutworm moths,Actebia fennica (Lepidoptera: Noctuidae), were determined for different types of traps and different dispenser loads of sex attractant. Of the five traps tested, highest catch (35 males/per night) was obtained with Uni-Traps, whereas Pherocon 1CP, Delta and Hara traps rapidly became saturated at 9, 6, and 11 males/per night, respectively. Multi-Pher traps, like the Uni-Traps, have a covered vertical cone with a large collecting bucket but only catch about 1/3 of the number of moths (9 males/per night) as the Uni-Traps, thus reducing potential saturation. Red rubber septa loaded with 500 μg of attractant blend gave a consistent catch for at least 60 days; 1000 and 2000 μg loadings lasted for a minimum of 90 days. Polyvinylchloride and red rubber septa dispensers containing 100 μg of attractant had similar catch rates, which decreased rapidly with age. Based on these trap and lure-loading experiments, Multi-Pher traps baited with 1000 μg of attractant in a red rubber septum were selected for future calibration studies between catch density and population fluctuations on susceptible sites. Two years of monitoring results also are reported.

AbstractEggs of western blackheaded budworm, Acleris gloverana (Walsingham), were found on the underside of needles of western hemlock, Tsuga heterophylla (Raf.) Sarg., with higher densities in the mid-crown area toward the outer tips of branches. Fringe and dominant trees were preferred oviposition sites over trees in lower crown classes or shaded positions. Vertical differences in needle density were considerable and led to high variability in insect densities when expressed on a per branch basis. When densities of eggs were based on a fresh branch weight basis there was a significant decrease in sample bias caused by the uneven distribution of foliage over the crowns.

The effects of trap design, lure concentration, lure age, and trap maintenance on the catch of western spruce budworm moths, Choristoneura occidentalis Freeman, in pheromone traps were tested in light to moderate infestations near Ashcroft, B.C. High cumulative moth catches reduced the trapping efficiency of both the sticky traps and the non-sticky Uni-traps relative to traps from which the moths were removed every 2 days. Correlations between the total season's catch and larval density per plot in the same and following generations were not significant (P > 0.05) for any of the eight combinations of trap design, lure concentration, and maintenance regimen tested. However, by dividing the mean moth catch in Uni-traps by either the basal area or foliage biomass per hectare in each plot, correlations with the following year's larval density were significant (r2 = 0.77-0.98; P < 0.05; n = 5).

AbstractThe sex pheromone components of the black army cutworm, Actebia fennica (Tauscher), were identified in abdomen-tip extracts from calling female moths. The primary pheromone component was (Z)-7-dodecenyl acetate. Although (Z)-11-tetradecenyl acetate was detectable only in trace quantities in the extracts, it was the major component in the best synthetic blend for attraction of male moths. The most effective synthetic blend was (Z)-7-dodecenyl acetate and (Z)-11-tetradecenyl acetate at a ratio of 1:20. No other component detected in the extracts increased trap capture of males when added to the two-component blend; however, (Z)-5-dodecenyl acetate, (Z)-7-dodecenol, and (Z)-9-tetradecenyl acetate reduced catches. This two-component blend will be useful for studying the habits of the adults and for population monitoring.

AbstractA sequential sampling system for early-instar Douglas-fir tussock moth larvae based on beating 3 lower branches from each of a number of trees is described. The relationship between lower- and mid-crown insect densities is given. The number of samples required to assess moderate insect densities using a fixed level of precision and at low insect densities using a critical density level is presented. The system is designed to be used during the early stages of an outbreak in stands not previously defoliated.

AbstractThe numbers of Douglas-fir tussock moths (Orgyia pseudotsugata) (Lepidoptera: Lymantriidae) caught in sticky, delta-shaped pheromone traps baited with different concentrations of synthetic lures were compared with egg-mass densities and subsequent defoliation throughout a population cycle. A lure containing 0.01% pheromone by weight in the form of a 3 × 5-mm polyvinylchloride rod provided more consistent catches than pheromone concentrations of 0.0001, 0.001, 0.1, or 1.0%. Trap saturation occurred when >40 moths per trap were caught. To achieve a standard error of 30%, 6 traps were required at each site. There was a poor correlation between numbers of moths caught and egg-mass density or defoliation estimates in the following generation, but a threshold density was found that provides a warning of an incipient outbreak. Ground surveys for egg masses are recommended to confirm suspected infestations after continuous increases in moth catches for 2 to 3 years or if an average of 25 moths or more per trap has been caught.

AbstractTwo different application methods were tested using a nuclear polyhedrosis virus as a control agent at an early stage in the outbreak cycle of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), in south central British Columbia in 1981. The virus, which often leads to the development of an epizootic late in the outbreak cycle, was propagated in whitemarked tussock moth, Orgyia leucostigma (J. E. Smith). A helicopter fitted with a boom and nozzle was used for treating four plots (total area 19.8 ha) at a dosage of 2.2 × 1011 polyhedral inclusion bodies (PIB) in an emitted volume of 11.3 L ha−1. Five to eight weeks after spraying, microscopic examination of live larvae showed that 77 to 100% were infected. In ground-spray applications of two other plots, a modified orchard-type sprayer was used to apply 2.4 × 1010 PIB in a volume of 4.5 L per tree. Microscopic diagnosis of live larvae at 8 weeks post-spray revealed 83 and 85% infection.In autumn 1981, no egg masses could be found in the plots treated earlier that year and no larvae were found on the sample trees in 1982 or 1983. The treatment was effective over a range of initial mean larval densities of 41 to 206 m−2 of foliage. At the same time, populations in nearby untreated areas increased in 1982. Little foliage protection was obtained the year of application due to the lengthy virus incubation period, but the trees recovered quickly when populations disappeared due to the virus epizootic.

AbstractA sequential egg-mass sample system for Douglas-fir tussock moth, Orgyia pseudotsugata McDunnough (Lepidoptera: Lymantriidae), was designed, based on visual scanning of the lower branches of Douglas-fir trees, Pseudotsuga menziesii (Mirb.) Franco. A branch was removed from each quadrant from the upper, middle and lower crown level, and from the lowest whorl of a total of 59 non-defoliated trees in 10 areas. No consistent trend in egg-mass density per branch could be found between crown levels and no level proved superior as a representative of the tree. Therefore, the lower whorl of branches was selected for survey purposes because of sampling efficiency. Sample stop lines were determined from egg-mass density and variability data collected on 55 sites and subsequent defoliation estimates were related to these densities. The system is designed as an early detection tool to be used only in non-defoliated stands at the incipient stage of an impending outbreak.

AbstractThe chemicals cis (Z) and trans (E)11-tetradecenyl acetate (11–14:Ac), trans 11-tetradecen-1-ol (E11–14:OH) and trans 11-tetradecenal (E11–14:Ald) were isolated from unmated female Choristoneura orae Freeman and shown to be highly attractive when used as lures in sticky traps. The identification of these components of the sex pheromone facilitates the separation of C. orae from other Pinaceae-feeding Choristoneura in the same area.

AbstractInvestigation of the European pine shoot moth pheromone has revealed three components in addition to the previously identified E-9-dodecenyl acetate (E9-12:Ac): E-9-dodecenol, dodecyl acetate, and dodecanol. Inclusion of E-9-dodecenol makes lures more attractive to the moth than unmated females or E9-12:Ac alone. Dodecyl acetate had no apparent effect when added to this more attractive mixture whereas dodecanol had an inhibitory effect. Dodecyl acetate appeared to mask the inhibitory effect of dodecanol when 0.3% or more of the former component is present in the lure. Relative proportions of components are critical in comparative testing or monitoring populations of the moth.