Cohorts of Pieris rapae (L.) (Lepidoptera: Pieridae) were reared at different temperatures on three substrates: plants in growth chambers, plants in field cages, and artificial medium. Pupal weight and larval development times were measured. The data were analyzed to determine the effect of temporal changes in substrate on pupal weight. When cohorts were reared on whole plants, average pupal weight declined with increasing time to pupation. For cohorts on potted plants in growth chambers, the rate of decline decreased as temperature increased from 15 to 27 °C. But, for cohorts on plants in field cages, the rate of decline increased as temperature increased from 16 to 25 °C. We speculate that the former trend resulted from plant deterioration, especially at low temperatures, and the latter from larval competition at high temperatures. When larvae were reared on potted plants to the late II or early III instar and then transferred to artificial medium, deterioration of the medium at temperatures below 20 and above 27 °C caused pupal weight to decline significantly with increasing time to pupation, whereas between 20 and 27 °C, pupal weight was constant or increased with increasing time to pupation. Development times of larvae from cohorts reared on plants in growth chambers showed no consistent differences from those of larvae from cohorts reared on artificial medium, at any temperature (overall averages: 187 and 184 day-degrees above 10 °C, on plants versus medium). Pupal weights are determined by the ratio of growth rate to development rate (Appendix). Therefore, the observed differences in pupal weight reflect differences in growth rates rather than differences in development rates. The results show that, depending on temperature, substrate deterioration may seriously affect laboratory studies of herbivore growth and that there are important interactions between temperature and host-plant growth conditions that may make extrapolation of laboratory estimates of herbivore growth to field conditions tenuous.

We used pitfall trapping to measure the species richness and relative abundance of ground beetles (Coleoptera: Carabidae) in four forest habitats on Kent Island, a 80-ha island in the Bay of Fundy, New Brunswick, Canada. Sixteen species of ground beetles representing 11 genera were identified in the forested habitats on Kent Island; the relative paucity of ground beetle species may be a result of the island’s harsh climate, dense colonies of breeding seabirds, and isolation from the mainland. Estimates of ground beetle population densities on Kent Island ranged from 50 000 to 250 000/ha. Most ground beetle species were trapped in all habitats and appeared to be habitat generalists. In a series of experiments in which we removed all ground beetles trapped daily over a 3-week period in two experimental plots, ground beetle densities remained as high as in a control plot; other ground beetles quickly moved into the experimental plots to replace beetles that had been removed. The density of ground beetles was highest in intact forest and large forest patches; in contrast, the density of invertebrates other than ground beetles (i.e., possible prey or competitors of ground beetles) was highest in open habitats and isolated forest patches, where ground beetles were less common. Removing ground beetles from experimental plots did not result in an increase in the density of other invertebrates.

Concentrations of organic N and minerals Ca, Fe, K, Mg, Na, P, and S in tissues of galls induced by Diplolepis spinosa (Ashmead) and Diplolepis triforma Shorthouse and Ritchie in growth and maturation phases were compared with those in ungalled tissues of host roses and tissues distal to galls to increase our understanding of nutritional relationships between gall wasps and their host plants (Rosa blanda Aiton and Rosa acicularis Lindley, respectively). Concentrations of N and most mineral nutrients were lower in galls than in ungalled tissues, and tissues distal to galls, suggesting that cynipids regulate rather than concentrate nutrients within their galls. Concentrations of mineral nutrients within the larvae of both species of inducers, and their parasitoids, were determined for galls in the maturation phase. Absolute amounts of most minerals in gall tissues were positively correlated with the number of inhabitants, indicating that control of translocation of nutrients to galls occurs on a per inducer basis. Concentrations of nutrients in mature larvae of parasitoids were the same as concentrations in mature larvae of inducers, which explains why parasitism of gall inducers had no influence on the concentrations or amounts of nutrients in galls. Galls of D. triforma had greater concentrations of N and most mineral nutrients than did galls of D. spinosa. Likewise, larvae of D. triforma, and the parasitoids feeding on D. triforma, had greater concentrations of N and mineral nutrients than did larvae of D. spinosa and its parasitoids. Galls of both species had different concentrations of nutrients compared with ungalled tissues and tissues distal to the galls. Galls of both species also had seasonal decreases in concentrations of nutrients. Parasitoids of each species of inducer were generally similar in mineral composition to their hosts.

A process-oriented model was recently developed to simulate the efficacy of spray products containing Bacillus thuringiensis Berliner subsp. kurstaki (Bacillaceae) against the spruce budworm, Choristoneura fumiferana Clemens (Cooke and Régnière 1996). The model accurately predicted foliage protection and larval population reduction during validation spray trials (Régnière and Cooke 1998; Cooke and Régnière 1999). The impact of treatment on budworm generation survival was generally well mimicked by the model except for a consistent overestimation of survival at the end of immature development in the treated plots. Régnière and Cooke (1998) speculated that residual mortality due to treatment may be occurring during the pupal stage. Carry-over of B. thuringiensis from larvae to pupae has been documented for spruce budworm (Klein and Lewis 1966) and several other Lepidoptera (Legner and Oatman 1962; Angus 1965). Although we recently investigated the response of spruce budworm larvae to ingestion of sublethal doses of B. thuringiensis (Pedersen et al. 1997), effects on pupal survival or adult emergence were not examined. In this note, we report the results of an experiment designed to assess such effects.

Host specificity of Pissodes strobi (Peck) from different geographic regions and genetic divergence of local host-associated weevil populations were studied in a series of experiments. Pacific coast P. strobi reared from Sitka spruce, Picea sitchensis (Bong.) Carr (Pinaceae), were unable to successfully colonize either eastern white pine, Pinus strobus L. (Pinaceae), or western white pine, Pinus monticola Dougl. ex D. Don., in a forced-infestation study on interplanted trees in New York. Reproductively mature field-collected P. strobi from British Columbia did not oviposit on eastern white pine in New York, but field-collected New York weevils successfully reproduced in Sitka spruce leaders in British Columbia. Unacceptability of eastern white pine for western P. strobi was shown to be under genetic control, rather than influenced by prior host experience on Sitka spruce. Pissodes strobi originating from Sitka spruce but reared one generation in the laboratory on the exotic Norway spruce, Picea abies (L.) Karst., were also unable to utilize eastern white pine as a host in a forced-infestation experiment in the field. Population genetic studies using allozyme electrophoresis found that P. strobi populations occurring on different host species within 2 km of each other had significant differences in allele frequencies in three out of four cases. These results suggest that P. strobi can exist as small breeding populations that can facilitate host specialization. Applied research on host resistance against P. strobi could target mechanisms that prevent western P. strobi from utilizing nonhosts such as eastern and western white pines.

An isolated stand of western white pine, Pinus monticola Dougl. ex D. Don, on Texada Island (49°40′N, 124°10′W), British Columbia, is extremely valuable as a seed-production area for progeny resistant to white pine blister rust, Cronartium ribicola J.C. Fisch. (Cronartiaceae). During the past 5 years, cone beetles, Conophthorus ponderosae Hopkins (= C. monticolae), have severely limited crops of western white pine seed from the stand. Standard management options for cone beetles in seed orchards are not possible on Texada Island. A control program in wild stands such as the one on Texada Island requires alternate tactics such as a semiochemical-based trapping program. Females of the related species, Conophthorus coniperda (Schwarz) and Conophthorus resinosae Hopkins, produce (+)-pityol, (2R,5S)-2-(1-hydroxyl-l-methylethyl)-5-methyl-tetrahydrofurana, sex pheromone that attracts males of both species (Birgersson et al. 1995; Pierce et al. 1995). The host compound a-pinene significantly increases attraction of male C. coniperda to pityol-baited traps in stands of eastern white pine, Pinus strobus L. (de Groot et al. 1998).

In laboratory experiments adults and nymphs of the western conifer seed bug, Leptoglossus occidentalis Heidemann, were allowed to feed on mature seeds of Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco. Weight-loss measurements and scanning electron microscopy provided strong supporting evidence for the use of simple radiographic diagnosis as a method of classifying feeding damage to seeds into four categories: light (greater than two thirds of seed contents remaining), moderate (one third to two thirds of seed contents remaining), severe (less than one third of seed contents remaining), and extreme (seed empty). Scanning electron micrographs showed the apparent depletion of lipid and protein storage reserves which was verified by quantitative analyses that showed significant loss of lipid and buffer-insoluble (crystalloid) storage protein from seeds in all damage categories. The amount of buffer-soluble (matrix) protein was reduced in seeds from the severe and extreme damage categories. The increase in buffer-soluble protein observed in lightly damaged seeds was likely due to the solubilization of crystalloid storage protein, as a result of its breakdown into smaller peptides. Our results suggest that through the action of both lipases and proteases, L. occidentalis can have a serious impact on the major storage reserves of conifer seeds. Moreover, our data suggest that L. occidentalis feeds in a different manner than the laceration and flushing method found in other seed-feeding Hemiptera.

The angiosperm bark volatile, conophthorin, was tested at release rates of 3.0 and 0.3 mg/24 h against the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, the spruce beetle, Dendroctonus rufipennis (Kirby), the pine engraver, Ips pint (Say), and the western balsam bark beetle, Dryocoetes confusus Swaine (all Coleoptera: Scolytidae). The responses of D. pseudotsugae, I. pini, and (in one of two experiments) female D. confusus to attractant-baited traps were disrupted by conophthorin in a dose-dependent manner. Dendroctonus rufipennis was not disrupted by conophthorin. Our results extend the repellent bioactivity of conophthorin to Ips DeGeer spp. and confirm earlier experiments with D. pseudotsugae. Conophthorin may have some utility in protecting susceptible timber from bark beetle attack.

Synthetic sex pheromones released in a loblolly pine, Pinus taeda L. (Pinaceae), seed orchard interfered with the ability of male coneworm moths, Dioryctria Zeller spp. (Lepidoptera: Pyralidae), to locate traps baited with sex pheromones or live females. Pherocon 1C® traps baited with synthetic pheromones or live conspecific females were hung near the center of two 1.2-ha circular plots during emergence of Dioryctria amatella (Hulst), Dioryctria disclusa (Heinrich), and Dioryctria merkeli (Mutuura and Munroe). In a paired design, trap catches for the mating-disruption treatment with synthetic pheromone dispensers consisting of three polyvinyl chloride rods placed in every tree were compared with the control treatment. Treatments were alternated at intervals of 2–3 d. Trap catches of D. amatella were reduced by 91% when plots were treated with 2.5 g/ha of Z-11-hexadencenyl acetate. Catches were reduced by 99.5% for D. disclusa and by 97% for D. merkeli when plots were treated with 12.5 g/ha of Z-9-tetradecenyl acetate, whereas catches of D. amatella were unaffected by this mating-disruption treatment. Daily disappearance of Z-9-tetradecenyl acetate from the dispensers averaged 0.46 g/ha or less. Manually placing dispensers on nylon lines in the tops of trees was an effective method for releasing synthetic Dioryctria pheromones in the orchard. These data suggest it may be feasible to prevent mating of Dioryctria spp. in pine seed orchards by using synthetic pheromones for mating disruption, but large-scale tests will be required to demonstrate cone protection.

Granary trials to determine the efficacy of an enhanced diatomaceous earth (DE) formulation (Protect-It™) at 0.15 kg DE/t grain to control grain-feeding beetles in barley, Hordeum vulgare L. (Poaceae), were conducted at Glenlea, Manitoba. During the test, the grain moisture content ranged from 11 to 13%, and grain temperature ranged from 27 to 2 °C. The bulk density of barley was reduced 10–20 kg/m3 by the addition of diatomaceous earth. Adults of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), were released onto the top surface of the grain of each granary, producing an average density of approximately 4 insects/kg grain. Using Berlese funnels to extract insects from grain samples there was a 95% reduction in adults and an 80% reduction in larvae found in treated grain compared with untreated grain, 1 month after releasing insects into the grain. There was a 95% or greater decrease in the total number of insects caught with probe pitfall traps in the treated barley compared with the untreated barley for all sampling dates. For the confined populations, 200 adult C. ferrugineus or Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) (red flour beetle) were held in screened jars in the grain until the end of October, and there was over a 99% reduction in both insect species, compared with insects held on untreated grain. These results indicate that this diatomaceous earth formulation can control C. ferrugineus in barley in granaries at 0.15 kg DE/t grain.

We investigated the factors responsible for changes in abundance of the spruce bud moth, Zeiraphera canadensis Mut. and Free. (Lepidoptera: Tortricidae) in one unmanaged and several managed (i.e., planted) young white spruce, Picea glauca (Moench.) Voss (Pinaceae), stands in northern New Brunswick, Canada. Spruce bud moth densities declined when one stand closed (branches from neighbouring trees overlapped) and had already declined in another similarly aged closed stand, but remained high on 8- to 22-year-old open-grown white spruce. Both the intrageneration survival rate and the egg-to-moth ratios increased when population densities increased, and generally decreased, although the egg-to-moth ratio fluctuated, during the population decline in a managed stand. Increases in intrageneration survival rates of spruce bud moth on 5- to 10-year-old trees were due to increased larval or pupal survival. Crown closure explained 76 and 81% of the variability in larval and intrageneration survival, respectively, in four managed stands. The strong inverse relationship between larval survival and degree of crown closure resulted in statistically significant but spurious relationships between larval survival and larval density and between larval survival and tree age. A reduction in larval survival occurring as degree of crown closure increased was the most important factor influencing decreases in intrageneration survival at the beginning of population decline. Increases in the egg-to-moth ratio during the population increase, and decrease during population decline, suggested that dispersal behaviour and (or) realized fecundity of females also contributed to annual changes in population.

The Colorado potato beetle, Leptinotarsa decemlineata (Say), overwinters in the soil as a diapausing adult. Large numbers of adult beetles fly and walk from potato, Solanum tuberosum L. (Solanaceae), fields to the surrounding forested edges late in the summer (Voss and Ferro 1990). This movement can result in higher densities of diapausing adults in the soil along these edges than in potato fields (Weber and Ferro 1993). Beetles that overwinter in these woody borders show lower levels of overwintering mortality (Weber et al. 1994). Survivorship of overwintering Colorado potato beetle adults was positively correlated with soil depth for studies conducted adjacent to potato fields in New Jersey (Lashomb et al. 1984) and Massachusetts (Weber and Ferro 1993). Lashomb et al. (1984) reported that a 10-cm increase in soil depth decreased winter mortality by 32%.

Field studies were conducted in the United States and Canada to determine the response of the white pine cone beetle, Conophthorus coniperda (Schwarz), and the red pine cone beetle, Conophthorus resinosae Hopkins, to two potential inhibitors, conophthorin and verbenone, of pheromone communication. Trap catches of male C. coniperda and C. resinosae were significantly reduced and generally declined with increasing concentrations of conophthorin in traps baited with the pityol, a female-produced pheromone. Verbenone did not significantly reduce trap catches of C. coniperda. Conophthorin, but not verbenone, significantly reduced cone attacks by C. coniperda when placed near cone clusters. The twig beetles, Pityophthorus cariniceps LeConte and Pityophthorus puberulus (LeConte), responded to traps with pityol and α-pinene baits alone or with conophthorin. Thanasimus dubius (F) (Coleoptera: Cleridae) was attracted to the pityol and α-pinene, but conophthorin had no effect on attraction of this generalist bark beetle predator. Verbenone significantly reduced trap catches of T. dubius in pityol-baited traps.

The potential for using synthetic sex pheromone to disrupt mating of spotted tentiform leafminers, Phyllonorycter blancardella (F.), was evaluated in four experimental and two commercial apple, Malus domestica (Borkh) (Rosaceae), orchards in Ontario during 1992 and 1993. The average disruption index [i.e., (total number of moths trapped in control plot – total number of moths trapped in pheromone-treated plot)/total number of moths trapped in control plot × 100] was 80.7% when leafminer pheromone, (E)-10-dodecen-1-yl-acetate, was evaporated into square, approximately 400-m2 plots. During the 2-year study, pheromone was evaporated into the pheromone-treated plots at an average hourly rate of 39.6 mg/ha. There was no relationship between the estimated release rate of pheromone and average temperature. There was a negative linear relationship between the disruption index and leafminer density, as measured by the number of moths trapped in the control plot. There was no relationship between the disruption index and the estimated release rate of pheromone. Our results suggest that it may be possible to control the spotted tentiform leafminer using sex-pheromone-mediated mating disruption.

The grape beny moth, Endopiza viteana (Clemens), is the key pest of cultivated grapes in the eastern United States and Canada (Gleissner 1943; Ker 1990). Laboratory techniques have been developed for large-scale rearing of this tortricid (Taschenberg 1951, 1969) using grape berries of Vitis vinifera L. (Vitaceae) and locally grown varieties. The use of grape berries is unsatisfactory because berries attract fruit flies, develop mold, and rot rapidly at normal laboratory temperatures (Taschenberg 1969). In this paper, we describe a diet for rearing E. viteana and the process that was undertaken in its development.

We used laboratory experiments to study the effects of rearing density on nymphal duration, dispersal dimorphism, and reproduction of two wing-dimorphic water strider species, Gerris buenoi Kirkaldy (wing morphs macropterous and micropterous) and Gerris pingreensis Drake and Hottes (mainly apterous and macropterous), that specialize, respectively, in temporary and permanent habitats. First-instar nymphs from field-collected or laboratory-cultured parents were reared with superabundant food at high (2900 or 3100 first-instar individuals/m2) or low (145 or 155 first-instar individuals/m2) starting density under a photoperiod of 19L:5D and at 20 ± 2 °C. Average nymphal period of both species under high density was significantly shorter by 4–5 d than under low density. There were no significant differences in percent survival between densities in either species. In G. pingreensis all new adults were apterous and entered reproductive diapause. In contrast, both wing morphs were expressed in G. buenoi; however, a lower proportion of macropters emerged under high density than under low density. All females of G. buenoi tested were reproductively active, regardless of wing morph. There was no effect of density on preoviposition period for G. buenoi of either wing morph, although preoviposition period was about twice as long in long-winged as in short-winged females. In G. buenoi, nymphal crowding promotes development of nonflying reproductives, which allocate nutritional resources to rapid reproduction rather than dispersal, at least when food conditions are sufficient. In G. pingreensis, nymphs that develop faster under crowding may be less subject to cannibalism and intraguild predation.

We used three sampling methods to identify the arthropod predators most abundant and active in fields of cabbage, Brassica oleracea L. var. capitata, and determined those most likely to be important predators of the imported cabbageworm, Pieris rapae L., by testing the predators’ abilities to forage on cabbage plants and to feed on Pieris rapae in small arenas in the laboratory. Abundance and activity in the field were monitored with pitfall traps, sticky traps applied directly to leaves, and plant samples. Four criteria were used to assess the species’ potential value as a predator of Pieris rapae in cabbage: relatively high overall abundance in trap catches and plant samples, occurrence on plant foliage in the field, a high propensity to feed on Pieris rapae eggs and first instars, and the ability to search for larval Pieris rapae on cabbage plants. Four species, the wolf spider Pardosa milvina (Hentz) (Araneae: Lycosidae), the harvestman Phalangium opilio L. (Opiliones: Phalangiidae), and the lady beetles Coleomegilla maculata lengi Timberlake and Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), demonstrated these attributes, although all four species appeared unable to search for prey on some parts of the cabbage plants, owing to unsure footing on the plants’ slippery cuticular wax. Linyphiids (Araneae) and syrphids (Diptera), the most abundant taxa in the plant samples, may prove better at thoroughly searching cabbage plants, but remain to be tested in future laboratory trials. Our results show that only a small portion of the predatory arthropod species that occur in cabbage fields is likely to prey on Pieris rapae on the plants, although important questions remain about the roles of some taxa. Future efforts to enhance biological control of Pieris rapae by naturally occurring predators can now focus on further elucidating and finding ways to enhance the roles of those predators that are effective.

The pine shoot beetle, Tomicus piniperda (L.), is an exotic pest that is regulated by federal quarantines in the United States and Canada. Mark–release–recapture experiments were performed with infested logs coated with fluorescent powder to determine if overwintering beetles in logs would leave a mill yard if infested logs were transported to sawmills in uninfested areas. Overwintering T. piniperda adults were marked with powder as they emerged in spring. Dispersal studies were conducted in four simulated mill yards and five operational sawmills to determine whether T. piniperda would colonize only the log pile in which they overwintered, fly to nearby log piles, or disperse beyond the mill yard. Each simulated mill yard was composed of 36 uninfested red pine logs, Pinus resinosa Ait. (Pinaceae), and 12 α-pinene-baited funnel traps set up to 100 m from a central release pile of six uninfested red pine and nine infested logs of Scotch pine, Pinus sylvestris L. At the five operational sawmills, baited funnel traps were set up to 400 m outside of each mill yard. Overall, 482 T. piniperda galleries were found on the experimental logs recovered from the four simulated mill yards combined. Tomicus piniperda adults dispersed and attacked the most distant logs at 100 m from the release point in the simulated mill yards. Likewise, adults were captured in baited funnel traps at distances up to 230 m in simulated mill yards and 250 m around operational sawmills. Although numbers of recaptured T. piniperda were generally low, in all cases some adults dispersed outside the mill yards despite the presence of abundant suitable breeding material. Therefore, logs containing overwintering adults pose a risk of spreading T. piniperda if not processed prior to initiation of spring flight.

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, attacks Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Pinaceae), throughout western North America. Periodic outbreaks cause increased mortality of its host. Land managers and forest health specialists often need to determine population trends of this insect. Bark samples were obtained from 326 trees distributed over 21 stands during a 2-year period in late winter to early spring of 1997 and 1998 in the Colorado Front Range. The variance to mean relationship of brood adults was examined using the Taylor power law, and a fixed-precision sampling plan was developed using Green’s method. Stop lines and minimum number of samples required to estimate brood adult density per 0.046 m2 with precision levels of 0.1, 0.2, and 0.3 were calculated. A resampling simulation conducted with an independent data set indicated that desired precision levels were not met. Theoretical precision levels were adjusted until desired precision levels were achieved. Average number of samples needed to estimate brood adult densities up to 25.1 adults per 0.046 m2 with precision levels of 0.09, 0.2, and 0.3 were 91, 20, and 8, respectively. For densities greater than 25.1 brood adults per 0.046 m2, conservative estimates are obtained with 72, 15, and 6 samples for precision levels of 0.09, 0.2, and 0.3, respectively. An emergence ratio can be obtained by dividing the estimated density of brood adults by twice the number of gallery starts. This system provides the user with an immediate assessment of the population trend of Douglas-fir beetle. The data collected compare favorably with data from other Douglas-fir beetle outbreaks reported in the literature. The use of this plan outside the Colorado Front Range, or by sampling at a different height, should be cautioned until additional data from other locations and sampling heights are examined.