The tri-trophic linkages associated with biological control of wheat midge, Sitodiplosis mosellana, in western Canada

Wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), is an important insect pest of cereal crops including wheat (Triticum aestivum L., Poaceae). Crop damage associated with wheat midge is caused by larval feeding on developing kernels. Several abiotic factors (i.e., timing of spring rainfall) and biotic factors affect the population dynamics of wheat midge, including its primary biological control agent of wheat midge in North America, Macroglenes penetrans (Kirby) (Hymenoptera: Pteromalidae). To better understand the tri-trophic linkages between wheat, wheat midge, and M. penetrans, we developed a phenology model using DYMEX, a mechanistic modelling program that incorporates abiotic and biotic parameters. The model was validated by comparing model outputs to field data, collected during annual surveys conducted in Saskatchewan, Canada, beginning in 1991. Our results indicate that the life history of M. penetrans is tightly linked with that of its host, S. mosellana, which we expected based on field observations. Using this model, we can use insect monitoring data, including data related to parasitism, to predict risk to wheat crops. Model predictions can be used, in turn, to help farmers make management decisions to protect their wheat crops from wheat midge damage, including planting midge tolerant wheat