Cabbage aphid control on commercial farms in the Thames Valley, UK

Abstract

Cabbage aphid control on June/July-planted cabbages was studied on four commercial vegetable farms in the Thames Valley and compared with an untreated crop at Silwood Park. At the four commercial sites, where growers followed their normal control practices, counts were made of aphids, their predators and parasites, throughout the cropping season and following the application of foliar insecticide sprays. Although natural enemies appear to be important in producing a mid-season trough in aphid numbers, they are unable to cope with the increase in aphid numbers later in the crop season. This problem of late aphid control is made worse because the effectiveness of foliar treatment also declines. At present, as the use of action thresholds does not seem feasible, it is suggested that improvements should be sought in more effective techniques of granular or foliar application.