Aphids were counted in situ and carabid beetle populations assessed by pitfall trapping between 1983–1985 in potato fields in Scotland treated with demeton‐S‐methyl (DSM) or untreated. Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) was the most abundant aphid. Nineteen species of carabid beetles were trapped but the fauna was dominated by Pterostichus melanarius (Ill.) and Pterostichus madidus (Fabr.) (Coleoptera: Carabidae). Pitfall trap catches of these carabids were variable but generally lower in sprayed than unsprayed plots for a few days after DSM application and higher a week or two later. Of 1800 P. melanarius and 910 P. madidus dissected, 14.4 per cent and 30.5 per cent respectively, contained aphid remains. The proportion that had eaten aphids often was higher in sprayed than unsprayed plots immediately after treatment. In additional experiments, aphids treated with DSM fell from plants; four to five per cent of the theoretically applied dose of DSM reached the ground in a closed‐canopy potato crop; and no mortality occurred when Pterostichus spp. were exposed to DSM in a field bioassay. It is proposed that observed patterns in trap catch of Pterostichus spp. around times of pesticide application may be due in part to aphids falling to the ground after treatment. Beetles that eat these fallen aphids may be less hungry, less active and less likely to be trapped. Later increases in catches may be attributed to hungry, more active beetles, a consequence of prey removal by the insecticide. Although this hypothesis requires further research, it is clear that the effects of insecticide treatment on carabid populations cannot be measured by pitfall trapping alone.

The lingonberry fruitworm, Grapholita libertina Heinrich, is a tortricid moth whose larvae infest wild lingonberry (Vaccinium vitis-idaea L. variety minus Lodd) Þelds in Newfoundland, Canada. This study investigated the potential for predicting G. libertina larval damage by using adult pheromone trap captures. Spatial patterns of capture were studied in relation to subsequent larval and damaged berry distributions in four wild lingonberry Þelds during 1998, 1999 and 2000. A model was tested that incorporated the effects of resource availability and coincident plant composition on insect distribution. In 1998 and 2000, the mean adult capture/trap correlated well with larval (R 2 ϭ 0.38 Ð 0.63) and damaged berry (R 2 ϭ 0.41Ð 0.59) density within grids at each site. In 1999, larval and damaged berry densities were not signiÞcantly correlated to adult distributions, and were more dependant on a limited host berry distribution (R 2 ϭ 0.54 and 0.47, respectively). The results of this study suggest that correlation between adult trapping of G. libertina and subsequent larval distributions is dependant on a minimal host berry population. Other factors that may contribute variability are also discussed.

The cabbage maggot, Delia radicum (L.), is a serious pest of cruciferous crops in temperate regions of North America and Europe. The effects of undersowing rutabaga, Brassica napus L. subsp. rapifera Metzg. (Brassicaceae), with white clover, Trifolium repens L. (Leguminosae), on second-generation cabbage maggot and its natural enemies were studied in Newfoundland in 1997 and 1998. In 1997, totals of 1311 and 724 eggs were recovered from bare and undersown plots, respectively. More eggs were present in bare plots than undersown plots on various specific dates. In 1997, rutabagas from bare plots weighed more than those from undersown plots, although damage ratings were similar, suggesting that competition, not cabbage maggot feeding, caused the yield differences. In 1998, there were few cabbage maggots present and little damage or yield reduction in either treatment. Similar numbers of cabbage maggot pupae were extracted and reared from each treatment in each year. In 1997, of the pupae reared from undersown plots, 48% produced cabbage maggot flies, 14% produced parasitic Hymenoptera, and 8% produced Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae); 19% of the pupae from bare plots produced cabbage maggot flies, 8% produced parasitic Hymenoptera, and 36% produced A. bilineata. More A. bilineata were captured in pitfall traps in bare plots than in undersown plots. The effect of clover on carabid beetles was species specific. There were more Bembidion lampros (Herbst) and Amara bifrons (Gyllenhal) in bare plots in 1997, and more Pterostichus melanarius (Illiger) in undersown plots in both years. Despite consistently lower egg numbers in undersown plots than in bare plots, the numbers of pupae in the two treatments were similar at the end of the season. We speculate that this may be due to differential, density-dependent mortality of immature stages of cabbage maggot caused by predators and parasitoids.

Continued range expansion of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is exposing new species of soft fruits and berries to potential infestation. Our understanding of cues that drive host-finding and selection in this highly polyphagous pest insect is still incomplete. Fruit firmness influences host choice behaviour by limiting suitability for oviposition and larval development. Other factors such as fruit sweetness and acidity act as cues for fruit ripening. Here we assess the role of these cues and fruit colour on host selection. We demonstrate that the use of objective and nonanthropocentric methods of quantifying colour in studies of colour preference is critical to understanding the cues evoking responses from insects. Acidity but not sweetness increased D. suzukii attraction and larval success. Differences in D. suzukii attraction were most strongly correlated with short-wavelength reflectance (blue, cyan, and green (470–560 nm)). Growers could select for fruit varieties with relatively higher reflectance values upon maturity to reduce susceptibility to D. suzukii.