Impact of Crop Phenology and Infestation Timing on Damage and Pest Management of the Swede Midge, Contarinia nasturtii (Diptera: Cecidomyiidae), in Canola
The relationship between canola, Brassica napus L., crop phenology and susceptibility to the swede midge, Contarinia nasturtii (Kieffer) was investigated to improve insecticide application timing recommendations and management of this invasive pest. Insecticide applications were more critical at vegetative and early bud stages than during secondary bud formation in studies of insecticide application timing based on growth stage conducted in growers’ fields over two years. However, treatment timing effects on swede midge damage and yield varied depending on field site. Laboratory studies were conducted to elucidate relationships between swede midge oviposition preference and density, crop stage, and damage and yield effects. A significant negative relationship was observed between swede midge density and canola seed yield and pod number, as well as the potential for damage compensation by secondary raceme growth. These results may contribute to the development of swede midge pheromone action thresholds and understanding the compensatory ability of canola.