Single aerial applications of Bacillus thuringiensis Berliner (Bt) to control infestations of the eastern spruce budworm (Choristoneura fumiferana Clemens) have had varied operational success. Double applications are too expensive for general use, but might prove useful if directed to areas where the initial application was unsuccessful. This requires forecasts of the efficacy of the initial application in operational spray blocks within 4–5 days.

Data were collected in 30 spray blocks in 1989 in a feasibility study to determine if such forecasts of spray efficacy could be made from the prespray budworm population density, N0, and from the proportion of the population that had ingested a lethal dose Bt within 2 days of application, M. A mathematical model forecasting the postspray budworm population density, NF, was derived from population-dynamic considerations and fitted (r2 = 0.48, p < 0.0001):

The proportion of current foliage defoliated, D, depended (r = 0.81) on N0 and on whether the block was sprayed (I = 0) or not (I = 1):

Only one measure of defoliation involved M in any statistically significant way. The predicted (from values of N0) proportion of defoliation prevented by Bt application, dD, was weakly (r2 = 0.25, p = 0.002) related to M:

The large proportion of the variation in efficacy that remains unexplained by the models involving M limits the operational utility of this approach as it now stands for specific sites. The potential for further development of these models as decision support tools for fairly large spray blocks is discussed in terms of improving the sampling plan and including additional predictor variables.

Methods are also presented that reduce bias in calculations of population reduction (Abbott 1925) and foliage protection when data are available from few control and many treatment blocks.

A laboratory method to screen crucifer seedlings for antixenosis resistance to flea beetles, Phyllotreta cruciferae (Goeze), is described. The method utilizes a plexiglass arena with a foam base to hold 30- by 50-mm vials containing individual seedlings of 10 entries (10 seedlings per entry) in a 10 × 10 layout. In each arena, nine test entries and a standard entry are compared in a Latin square design. Flea beetles are allowed to feed on seedlings for about 30 h, and then the damage to individual seedlings is estimated using a visual rating scale. A rating of one arena can be completed in about 15 min. Seedlings at the arena edge often suffer more damage than those in the centre of the arena, but the effect of this variability in damage is minimized by the Latin square design. Use of border (guard) rows and columns does not eliminate the edge effects. The use of arenas without borders, and a single damage rating where the damage to the standard entry is about 50% of the cotyledon area, are considered ideal for initial screening to identify sources of flea beetle resistance. The method detects entries that differ by as little as 18% damage using a single arena with 10 replicate seedlings per entry. No significant antixenosis was found among 19 cultivars of Brassica napus L. and B. campestris L., but one accession of B. carinata L. and two accessions of Sinapis alba (L.) exhibited antixenosis.

Two artificial pupation shelter types were compared as Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), monitoring methods in El Dorado County, CA. No difference in attraction was found; wood shelters are recommended as they are both inexpensive and durable. Shelters were compared with three-crown-level larval sampling and with pheromone trapping. Cocoon counts from shelters were significantly correlated with same-year larval density, reflecting larval sample differences between ridges and the general trend in plots along ridges. Egg masses from shelters in 1978 were significantly correlated with the next year’s larval counts, and are of potential value as an early predictor of larval population. The shelter method also provides information on adult sex ratio and pupal and egg emergence, parasitism, and predation.

The effectiveness of topical applications of the juvenile hormone analog Fenoxycarb against selected developmental stages of the eastern spruce budworm, Choristoneura fumiferana (Clemens), was determined. Eggs at an early stage of embryogenesis (0–24 h old) were prevented from hatching and were more sensitive to the compound than older eggs (48–72 h old) and larval stages. Fifth-instar larvae displayed lethal morphogenetic effects following Fenoxycarb treatment, but third-instar larvae were refractory. Adult females constituted the most sensitive stage; treated insects laid eggs that failed to hatch. Untreated adult females that mated with Fenoxycarb-treated males also laid infertile eggs.

Morphological and physical characteristics of plants, such as trichomes (pubescence), surface waxes, silication, toughness, sclerotization, colour, and shape may affect herbivory by providing inhospitable surfaces or by eliciting altered host behaviour (review by Noms and Kogan 1980). Even slight variations in the morphological structure of plants may enhance their fitness and form the basis of resistance. Seedlings of the hybrid cabbage, Brassica oleraceae L. cv. Survivor, provide an intriguing opportunity to study within the same plant the influence of radically different cotyledon morphology on the feeding behaviour of the crucifer flea beetle, Phyllotreta cruciferae Goeze, because a high proportion of seedlings of this cultivar (>92%) have one folded cotyledon. The condition arises from a failure of the inner cotyledon of the embryo to open fully and assume a normal horizontal plane after germination. The outer cotyledon is invariably normal and both cotyledons appear to grow at about the same rate (unpublished data). The degree of folding varies from cotyledons that are only a few degrees from horizontal to those that are fully folded and 90° from horizontal. This study reports the distribution and feeding of P. cruciferae on the morphologically different cotyledons of B. oleraceae cv. Survivor.

The placement of yellow sticky traps in relation to greenhouse-grown tomato plants affected the number of greenhouse whiteflies captured on traps. Whiteflies were caught on traps close to the ground when the traps were 1.0 m or more from plants, and were caught on traps level with the point from which they started flight when the traps were 0.5 m from plants. Traps 1.0 m from plants primarily caught whiteflies less than 5 days old, and trap catches were not correlated with numbers on plants; traps 0.5 m from plants caught whiteflies of all ages, and trap catches were correlated with numbers on plants. These results suggest that under field conditions greenhouse whiteflies would behave much like other species of whitefly, and would tend to be caught on traps close to the ground. In greenhouses, monitoring traps should be placed close to and slightly below the tops of the plants. Trap counts could be treated as samples from individual plants and used to make an estimate of population size in the greenhouse. Traps placed further from the plants monitor flight activity only.

Development and survival of the predatory pentatomids Podisus maculiventris (Say) and Podisus sagitta (Fab.) were studied at six constant temperatures ranging from 19 to 35 °C. Time required for development from egg to adult ranged from 48.9 days (19 °C) to 18.9 days (30 °C) for P. maculiventris and from 51.9 days (19 °C) to 16.9 days (33 °C) for P. sagitta. At 33 °C, eggs of P. maculiventris did not hatch and development of nymphs that had emerged at 23 °C was retarded; none of the first-instar nymphs incubated at 35 °C survived the next moult. A constant temperature of 35 °C was fatal to P. sagitta eggs and extended the developmental period of nymphs from 23 °C. Egg hatch ranged from 47% (19 °C) to 57% (27 °C) for P. maculiventris and from 54% (33 °C) to 71% (27 °C) for P. sagitta. Nymphal survival was high at moderate temperatures, with 63–78% and 65–82% of the first-instar nymphs of the respective species reaching adulthood. Mortality during the nymphal stage was significantly increased at high temperatures, but was considerably lower for P. sagitta than for P. maculiventris. Lower threshold temperatures for egg and nymphal development were estimated to be 10.7 and 11.7 °C for P. maculiventris, and 13.3 and 12.2 °C for P. sagitta. Thermal requirements for these stages were 78.2 and 275.5 degree-days, and 60.9 and 265.5 degree-days, respectively. These observations suggest that P. sagitta is somewhat better adapted to high temperatures than is P. maculiventris.

The alfalfa leafcutting bee, Megachile rotundata (Fab.), is a domesticated pollinator important for alfalfa seed production in western Canada. Populations of M. rotundata are highly susceptible to chalkbrood, a disease caused by the fungus Ascosphaera aggregata Skou. The disease has caused high mortalities in M. rotundata populations in the northwestern United States since 1972. It was found in Manitoba in 1982, Alberta in 1983, and Saskatchewan in 1984 (Richards 1985). In subsequent surveys, A. aggregata has been detected only sporadically and at low levels of infection in Saskatchewan M. rotundata populations (Goerzen 1991). A previously reported observation of A. aggregata in the native leafcutting bee M. relativa Cresson (Goerzen et al. 1990) indicated that the disease is present in native leafcutting bee species which commonly immigrate into alfalfa leafcutting bee nest material.

We show that Lasioglossum mediterraneum (Blüthgen) (Hymenoptera, Halictidae) is a species distinct from L. laticeps (Schenck) based upon electrophoretic analysis of 39 allozyme loci for sympatric populations collected from the Dordogne region of France. The genetic identity between the two is below average for sibling species of insects: no fewer than 10 fixed allelic differences were found. In contrast, allopatric L. laticeps populations (from the Dordogne and Paris) are genetically almost identical (I = 0.998). Heterozygosity estimates for both species are low, as is often the case with Hymenoptera. Diagnostic characteristics that can be used to separate the two species are described. A phylogeny for nine species of the subgenus Evylaeus is constructed from allozyme data.

A laboratory study of the fecundity, longevity, and intrinsic natural rate of increase of Epidinocarsis lopezi (De Santis) (Hymenoptera: Encyrtidae) was performed at 26 °C, the average temperature observed in the Congo during pullulation of its host Phenacoccus manihoti Mat.-Ferr. (Homoptera: Pseudococcidae). With 30 mealybugs per female per day, the parasitoid lives for an average of 41.4 days and lays 558.5 eggs. The net reproduction rate (R0) was calculated to be 269.9 females per female per generation, the average duration of a generation (T) was 33.9 days, and the intrinsic natural rate of increase of the parasitoid (rm) was 0.213. The fecundity observed in E. lopezi in this study was much higher than the figures previously reported. The rm of the parasitoid appeared to be higher than that determined by other authors for the mealybug. The limits of such a comparison are discussed.

Semiochemical-mediated behavior of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae), has received extensive study. In selecting and mass-attacking hosts in nature, it utilizes a blend of volatiles, including the aggregation pheromone, lineatin, and the host kairomones α-pinene and ethanol (MacConnell et al. 1977; Vité and Bakke 1979; Borden et al. 1982; Bakke 1983; Lindgren et al. 1983). In single cell recordings of European T. lineatum olfactory cells, Tømmerås and Mustaparta (1989) reported no response to pheromones of other scolytid species. However, Benz et al. (1986) reported some response in the field by European T. lineatum to a blend of synthetic Ips typographus (L.) pheromones, although a single attractant was not identified. We report that frontalin, a pheromone utilized by numerous Dendroctonus spp., is an attractive kairomone for T. lineatum in western North America.

The competition between Orius tristicoior (White) and Amblyseius cucumeris (Oude-mans), both preying on western flower thrips, Frankliniella occidentaiis (Pergande), was assessed. On single leaves in smail cages, mortality of A. cucumeris due to O. tristicoior was inversely proportional to thrips density; thrips mortality due to O. tristicoior was unaffected by A. cucumeris density. The proportion of A. cucumeris in the prey eaten was consistently less than its proportion in the prey initially available, both when thrips density varied and when A. cucumeris density varied. These relationships held for both immature and adult thrips. These results suggest that O. tristicoior and A. cucumeris could be used simultaneously for biological control of western flower thrips in greenhouse vegetable crops.

The impacts of the pyrethroid PP321 on the mite fauna in an apple orchard were studied at the Smithfield Experimental Farm of Agriculture Canada, Ontario, from 1988 to 1989. Two predacious mites, the phytoseiid Amblyseius fallacis (Garman) and the stigmaeid Zetzellia mali (Ewing), were affected by pyrethroid applications. The highest numbers of predators were found in untreated trees, and the lowest numbers were found in the trees treated with the higher rate of the pyrethroid (P < 0.05). Zetzellia mali has roughly the same susceptibility to PP321 as does A. fallacis. Two species of tetranychid phytophagous mites, the European red mite, Panonychus ulmi (Koch), and the twospotted spider mite, Tetranychus urticae Koch, were positively associated with pyrethroid applications. Significantly higher numbers of these mites were found in the pyrethroid-treated trees than in untreated ones (P < 0.05). Another phytophagous mite, the apple rust mite, Aculus schlechtendali (Nalepa) (Eriophyidae), was strongly suppressed by PP321 applications. Lower rate applications of the pyrethroid allowed more predators to survive, and resulted in lower abundances of tetranychid mites than did the higher rate. Therefore, reduced rates of pyrethroids may prove to be compatible with integrated control of spider mites in apple orchards.

Importance of cultivars, harvest schedules, and pest infestations as determinants of alfalfa, Medicago sativa L., productivity and stand persistence was investigated using the unimproved “OK08” (Oklahoma Common) and the multiple-pest resistant “WL 318” cultivars. Beginning in the 5th year of production, treatments including three first-harvest schedules (early bud, early bloom, and full bloom) were imposed in a factorial arrangement with unsprayed subplots and three pesticide options for control of alfalfa weevil, Hypera postica (Gyllenhal), or weeds such as downy brome, Bromus tectorum L., or both. In addition to estimating population levels of alfalfa weevil and percentage composition of weeds in forage during each year, alfalfa dry matter yield and stem densities (no. per square metre) were determined during the 3-year period from 1986 through 1988. The seasonal forage production (2-year mean) of WL 318 was nearly 5.4 Mg per hectare greater than that of OK08. There was no consistent trend for greater seasonal alfalfa yield with any of the first-harvest schedules. Timely application of pesticides, as well as use of the improved cultivar were essential for maintaining productivity in years 5 through 7 of stand life. At the termination of the study, only the herbicide + insecticide treatment of WL 318 had close to sufficient stem (and plant) numbers remaining for continued production.

The intra-nest transmission of two aromatic components of honey bee queen mandibular gland pheromone, 4-hydroxy-3-hydroxyphenylethanol (HVA) and methyl p-hydroxybenzoate (HOB), is quantitatively described. After being secreted onto the body surface of the queen, the greatest quantities of HVA and HOB are removed by workers in the queen’s retinue, especially those contacting the queen with their mouthparts. Other workers acquire pheromone components via direct contact with retinue bees or with other workers that have already acquired queen pheromone. HVA and HOB can also reach workers through queen or worker "footprints," although the relatively little material deposited onto the comb wax becomes less available with time, presumably because of diffusion into the wax. Pheromone material is removed from circulation by being internalized into workers, the queen, and the wax. Rates of HVA and HOB transfer between different entities within the nest are described in terms of pseudo first-order rate constants. The intra-nest transfer of these two components, both qualitatively and quantitatively, is similar to that described earlier for the most abundant queen mandibular gland pheromone component, 9-keto-2-(E)-decenoic acid (9-ODA; Naumann et al. 1991). Thus, the queen mandibular gland pheromone complex is transferred through the nest as a unit rather than as individual components moving at different rates.

The relationship between temperature and rate of development is described for Cephalonomia stephanoderis Betrem, an imported ectoparasitoid of the coffee berry borer Hypothenemus hampei (Ferrari).

For all stages, development rate increased linearly with temperature between 17 and 32°C. However, at 37°C both eggs and larvae died. When the parasitoid constructed a cocoon, the lower developmental threshold (t) varied from 11.8°C in the eggs to 14.2°C for pupae; when no cocoon was constructed, it varied from 11.8°C for the eggs to 14.3°C for pupae. The lower developmental threshold, from egg to adult, was 13.7°C (with cocoon) and 13.8°C (without cocoon). As these differences were small in relation to the standard errors of the estimates, they were not considered different. Because C. stephanoderis always constructs a cocoon under field conditions, the threshold temperature of 13.7°C seems to be the most suitable.

Physiological time expressed in degree-days (DD) for the egg to adult cycle of C. stephanoderis is 252.7 ± 45.3 DD (α = 0.05) when a cocoon is constructed, and 242.5 ± 35.1 DD (α = 0.05) when pupation occurs without construction of a cocoon.

Actinocephalus sp., a eugregarine protozoan, is reported from June beetles, Phyllophaga Harris, in southern Quebec. It is the first record of a protozoan infecting scarab beetles in Canada. The gregarine was found in 4.52% of the 16 930 Phyllophaga grubs collected from 45 localities during a 3-year study. The infection was endemic to the grub stage of the scarab beetle and sub-enzootic in grub populations throughout the survey area, never reaching epizootic proportions. Infection rates for other stages of the life cycle of Phyllophaga were insignificant. The study showed that the gregarine had a negligible impact on the population of the host insect.

One of the more frequently used methods of sampling flying insects is the sticky trap. These traps are often used to evaluate the type and size of prey available for aerial insectivores, such as bats and birds (e.g. Barclay 1991; Brigham 1992). Non-attractant sticky traps are favoured because they are considered relatively bias-free, yielding a more representative sample than attractant traps (Service 1976). Sticky traps are versatile in that they are simple to construct and operate, portable, and relatively inexpensive. When using these traps, it is possible to sample insects economically in similar or different habitats and at various heights within habitats (Kunz 1988).

Stress caused by two biocontrol agents on their weed host Canada thistle [Cirsium arvense (L.) Scop., Asteraceae] was investigated. The combined attack of the gall-fly Urophora cardui (L.) (Diptera: Tephritidae) and the stem-mining weevil Ceutorhynchus litura (F.) (Coleoptera: Curculionidae) caused a significant reduction in the vigour of the attacked plants as measured by the number of live buds in the 1st year and by the dry weight of the roots in the 3rd year. The attacks did not significantly reduce the number of aborted buds, mature seed heads, and new shoots, nor the combined dry weight of the leaves, stems, and galls as compared with Canada thistle plants that had not been galled or mined, in any of the 3 years. Non-structural carbohydrate content of the roots of attacked shoots was found significantly reduced only at the end of the mining period.

Widespread defoliation of sugar maple stands due to pear thrips, Taeniothrips inconsequens (Uzel), feeding occurred in Massachusetts in 1987 and 1988. To assess the role of tree health as a possible cause of these outbreaks, an experiment was conducted in sugar maple stands in Massachusetts in 1990. Sleeve cages were placed on mature sugar maples and stocked with adult female pear thrips to determine the relation between root starch reserves (an index of tree health) and thrips fecundity. The experiment was run at four sites, assessing both root starch levels and thrips fecundity on individual trees. Each stand showed a range from high to low starch values and trees at each end of the root starch index spectrum were selected for use in the experiment at each site. Analysis of data showed no differences between sites, apart from those linked to starch levels, and found thrips fecundity to be positively correlated with higher starch reserves. The results of this experiment do not support the original hypothesis that declining tree health was a causal factor in pear thrips outbreaks on sugar maple in Massachusetts.