MidgEmerge, a new predictive tool, indicates the presence of multiple emergence phenotypes of the overwintered generation of swede midge

The swede midge, Contarinia nasturtii (Kieffer) (Diptera: Cecidomyiidae), is a pest of cruciferous crops (Brassicaceae) in Europe and North America with high potential for economic impact. Effective timing of insecticide applications for swede midge control is difficult, in part due to a short adult lifespan. Predictive models are often used in integrated pest management programmes to facilitate the timing of control strategies. A European model, Contapré, for predicting adult swede midge emergence was shown to be inaccurate under Ontario field conditions. A new predictive model, MidgEmerge, was developed using DYMEX™ modelling software. MidgEmerge accurately predicts swede midge emergence in both Ontario and Québec. Observed emergence patterns cannot be explained without the presence of multiple emergence phenotypes. MidgEmerge indicates that there are two emergence phenotypes of the swede midge, each completing four generations per year in southern Ontario. A fifth generation of each may become possible with climate change. Evidence of a possible third emergence phenotype is presented. MidgEmerge has the potential to be an important predictive tool to inform and direct integrated pest management practices targeted against swede midge in North America.