Crucifer flea beetle, Phyllotreta cruciferae (Goeze) and striped flea beetle, Phyllotreta striolata (Fabricius) (Coleoptera: Chrysomelidae) are the most chronic and economically important flea beetle pests of cruciferous (Brassicaceae) crops in western Canada. There have been reports that populations of P. striolata are increasing in numbers and expanding their geographic range. Climate is the fundamental factor regulating the distribution and abundance of most insect species. Bioclimate simulation models of the two flea beetle species were developed to assess climatic factors influencing shifts in their geographic distribution and density. The results fostered a better understanding of how the two species responded to selected climate variables. Growing seasons with above average precipitation were predicted to favour the geographic distribution of P. striolata more than P. cruciferae. Both P. cruciferae and P. striolata were sensitive to temperature changes in the range of −2 °C to +2 °C. The ecoclimatic index (suitability index) for P. cruciferae increased with increasing temperatures, whereas the index for P. striolata declined with increasing temperatures. This study highlights the regions of the Prairies and Boreal Plains Ecozones that are most sensitive to shifts of the two populations and which may require changes in insecticidal seed treatments for effective control.

Both the striped flea beetle, Phyllotreta striolata (Fabricius), and crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), are invasive alien species to North America. In western Canada, they are the most significant insect pests of cruciferous (Brassicaceae) crops. Climate is the one of the most dominant factors regulating the geographic distribution and population density of most insect species. Recent bioclimatic simulation models of the two flea beetle species fostered a better understanding of how the two species responded to selected climate variables. They demonstrated that selected climate variables increased population densities and geographic range of the two species. General circulation model inputs were applied in this study to assess the impact of a changing climate on the response of P. cruciferae and P. striolata populations. Model output, using the climate change scenarios, predicted that both P. cruciferae and P. striolata populations will shift north in future climates and the degree of geographic overlap between these two species will be greater than for current climate. This suggests that the two species could potentially cause economic losses over an expanded area in the future.

Wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), Palaearctic in origin, is thought to have been introduced into North America in the early 1800s. It is a major pest of spring wheat (Triticum aestivum Linnaeus (Poaceae)), durum wheat (T. durum Desfontaines), triticale (X-Triticosecale), and, to a lesser extent, spring rye (Secale cereale Linnaeus (Poaceae)) throughout the northern Great Plains. Climate is the principal factor regulating the distribution and abundance of most insects. A bioclimate simulation model was developed to explain the current distribution and abundance of S. mosellana. The current distribution for North America, Europe, and Asia was consistent with model projections. General circulation model scenarios (CSIRO-MK 3.0 and MIROC-H) for the 2030 and 2070 time periods were applied to the bioclimate simulation model of S. mosellana to assess the potential impact of changing climates on their distribution and relative abundance. Potential changes to relative abundance and distribution were most sensitive to time period, as opposed to climate change scenario. Differences between the MIROC-H and CSIRO-MK 3.0 models were restricted to particular regions in North America. The study found that the range and abundance of S. mosellana, and associated crop risk, was predicted to expand in a northerly direction and contract across the present southern limits.

The effects of the biologically derived insecticide spinosad on parasitoids of Mamestra configurata Walker were studied. Adult Trichogramma inyoense Pinto and Oatman (Hymenoptera: Trichogrammatidae), an egg parasitoid, were as susceptible to a dose of 0.125 μg/cm2 as they were to a high dose of 2.0 μg/cm2. Application of spinosad to host eggs at the time of oviposition resulted in significantly reduced T. inyoense parasitism and higher parasitoid mortality in parasitized eggs. Adult Microplitis mediator (Haliday) (Hymenoptera: Braconidae), a larval endoparasitoid, were highly susceptible at the highest dose tested, 1.0 μg/cm2. Spinosad at 2.0 μg/cm2 fed to larval M. configurata parasitized with M. mediator 1 and 7 d previous caused similar mortality to that for nonparasitized larvae. At a dose of 0.125 μg/cm2, only larvae parasitized 1 d previously showed mortalities similar to those of nonparasitized larvae, whereas larvae parasitized 7 d previously were not affected by this low dose. Larval M. mediator that egressed from hosts parasitized 7 d previously and treated with the low dose were unable to complete cocoon formation and died. This study suggests that integrated pest management programs for M. configurata in canola should include evaluating the presence and abundance of parasitoids.

The efficacies of cypermethrin, deltamethrin, permethrin, endosulfan, methoxychlor, carbofuran, chlorpyrifos, dimethoate, and malathion were evaluated against the wheat midge, Sitodiplosis mosellana (Géhin). Methods are described for evaluating damage and protection in individually collected wheat heads and whole plants. Weighted values from whole plants provided the best indication of kernel protection and yield response.

Whole plants contained three main types of wheat heads (primary heads, first tillers, and second tillers) which differed in their frequencies, kernel numbers, and developmental times. The latter indicated that the chronology of midge attack, status of midge infestations during spraying, and spray coverage also differed in the head types.

Insecticides provided different levels of kernel protection within and among the various head types. The majority of primary heads emerged before spraying and harbored midge eggs at spraying. In these wheat heads, chlorpyrifos, endosulfan, and malathion provided significantly better kernel protection (60–75%) than permethrin, deltamethrin, and cypermethrin (<7%). The results suggested that the more effective kernel protectants permeated the spikelet and controlled the eggs and/or newly hatched larvae. Kernel protection in the primary heads was closely related to insecticide volatility. Conditions were different in most first tillers and second tillers which emerged after spraying. In these wheat heads, poor spray coverage and short residual activity against adult midge appeared to limit kernel protection by all insecticides.

Evaluations of individually collected wheat heads and whole plants indicated that several factors may influence the efficacy of aerial sprays against the wheat midge, Sitodiplosis mosellana (Géhin). These factors related to methods of assessing midge damage, condition of wheat heads during spraying, and methods of spray application. Location- and distribution-related influences also were important.

Efficacy assessments were based on reductions in midge larvae, midge-damaged kernels, and percentage kernel damage. The latter data were confounded by differences in kernel numbers within wheat heads. In head and plant samples, sprays were more effective at reducing numbers of midge larvae than reducing the incidence of midge-damaged kernels. Evaluations of individual heads overestimated the efficacy of sprays in whole plants which contained one primary and two tiller heads. Sprays provided more effective midge control and kernel protection in the primary heads, which emerged before spraying, than tiller heads, which emerged mainly after spraying. Protection was usually better in apical than basal regions of each head type. In whole plants, efficacy declined as tillering increased.

Plant evaluations indicated that the high-volume (37.4 L water per hectare) chlorpyrifos spray provided the best midge control and kernel protection (95% and 87%, respectively), followed by the low-volume (18.7 L water per hectare) chlorpyrifos spray (87% and 76%, respectively), and low-volume dimethoate spray (66% and 53%, respectively). When improvements in both yield and grade were considered and calculations based on 1987/1988 wheat prices, net returns from the three aerial sprays ranged from $62 to $113 Canadian per hectare. Long-term benefits of the sprays probably were less favourable. Reduction in wheat midge after spraying would negate the benefits of an egg–larval parasite, Pirene penetrans (Kirby), which was present in low numbers.

In a 3-year field study, potted plants of ‘Katepwa’ wheat, Triticum aestivum L., were exposed to ovipositing wheat midge. Sitodiplosis mosellana (Géhin), to determine when spikes are most susceptible to damage. After exposure, plants were maintained under controlled conditions for 4 weeks and examined for wheal midge larvae and damaged kernels, ‘Katepwa’ wheat became susceptible to wheat midge damage shortly after spikes emerged from the boot leaf. Location of larvae and damaged kernels within spikes was influenced by the duration spikelets were exposed to oviposition and pattern of anthesis within spikes. In 1992, frequencies of larvae and damaged kernels were 60–90 times higher in spikes exposed to oviposition during advanced heading (stages 57–59, Zadoks’ code) than in those exposed during flowering (stages 61–69). Kernel damage in spikes exposed to oviposition during stages 57–59, 61–65, and 65–70 was 48.5, 3.2, and 0.2%, respectively, in 1993 and 21.2, 1.0, and 0.6%, respectively, in 1994. Data indicated that susceptibility to midge damage declined 15- to 25-fold between heading and early anthesis and 35- to 240-fold between heading and advanced anthesis. Potential factors contributing to these declines and concomitant reductions in larval frequencies are discussed.

Commercial fields of ‘Katepwa’ wheat should be monitored for ovipositing wheat midge throughout heading (stages 51–59) when spikes are most vulnerable to damage. Larval survival and kernel damage were so low after stage 61 that monitoring during anthesis should be unnecessary. Intensive inspection of fields throughout heading would ensure that chemical treatments are applied when they are necessary and most effective.

Foraging honey bees were offered various sucrose–herbicide solutions. Despite the visual attractiveness of the feeding dishes to foragers, six of seven herbicides significantly reduced the incidence of feeding and were judged to be olfactory and gustatory repellents. The most repellent herbicide was 2,4,5-T, which totally inhibited feeding at concentrations as tow as 1000 ppm. The next most repellent was 2,4-DB, followed by linuron, picloram, 2,4-D, and monuron. Paraquat was the only herbicide that did not exhibit marked repellency at concentrations up to 4000 ppm.

The implications of these findings are discussed in terms of the impact of herbicide applications on honey bee foraging behaviour, brood development, pollination, and honey production.

Laboratory experiments were conducted to evaluate the contact and oral toxicity of commercial formulations of spinosad and deltamethrin to adults of the crucifer flea beetle, Phyllotreta cruciferae (Goeze). Method of exposure had a significant effect on flea beetle mortality and feeding damage to canola seedlings. Topical treatment of flea beetles with deltamethrin or different concentrations of spinosad resulted in significantly lower mortality and higher feeding damage than exposure to treated canola cotyledons. Results indicated that spinosad was more toxic by ingestion than by topical contact. Mortality from treated cotyledons was significantly higher with 60 ppm deltamethrin than with 80 or 120 ppm spinosad after 24 h exposure but not after 120 h exposure. Delayed mortality in the spinosad treatments did not result in high feeding damage; damage after 120 h was not significantly different in the spinosad and deltamethrin treatments. Low concentrations of spinosad (40 ppm) strongly inhibited feeding activity within 24 h after exposure. Mortality from spinosad was higher after beetles were exposed to treated cotyledons for 120 h than for 24 h. Mortality from spinosad, but not deltamethrin, was significantly higher at 25 °C than at 15 °C. An ionic surfactant, polyethylenimine, increased the toxicity of 40 ppm spinosad. Our study suggests that spinosad has potential for use as an insecticide against crucifer flea beetles on canola.