With the trend towards crop diversification, there has been a gradual increase in production of crucifer oilseed crops (canola and mustard) in the Prairie Ecozone of western Canada. Developments in germplasm of Brassica spp. and Sinapis alba L. have resulted in cultivars with improved drought resistance, making them more acceptable for production in arid regions of the prairies. This, in turn, has resulted in increased overlap in areas of grasshopper infestation and oilseed production. Grasshoppers are the most chronic insect pests of annual crops in the Prairie Ecozone. The primary threat to production of annual crops arises from migration of the hatchling populations into cropland from roadsides, headlands and field margins at the beginning of the growing season. As a result, grasshopper damage is most acute at the early stages of crop growth.

In this study, the impact of early season grasshopper feeding on canola and mustard crops was quantified in field studies, 1996 to 1998. Immatures of Melanoplus sanguinipes (the lesser migratory grasshopper) were allowed to damage eight Brassicaceae cultivars and breeding lines of four species: Brassica juncea Czern (‘AC Vulcan’ and ‘J92-223’), B. napus (‘AC Excel’ and ‘Midas’), B. rapa (‘AC Parkland’ and ‘Echo’) and S. alba (‘AC Pennant’ and ‘Ochre’). The overall yields of defoliated plants were 27.8% less than those of control plants (p = 0.0001). Yield reductions were greatest for AC Excel (47%) and least for AC Vulcan (19.6%). The results are discussed in the context of grasshopper management strategies.