Insect Pest Incidence and Injury to Herbicide‐Tolerant Canola in Western Canada

Abstract

Genetically modified herbicide‐tolerant (HT) canola (Brassica napus L.) cultivars dominate the acreage planted to this oilseed crop in western Canada. We conducted a 3‐yr (2000–2002) field study near Lethbridge, AB, Canada to compare the incidence and damage of three key insect pests in Roundup Ready, Liberty Link (both HT), and Q2 (a conventional cultivar). Flea beetle (Phyllotreta cruciferae and P. striolata [Coleoptera, Chrysomelidae]) damage in 2000 ranged from 31 to 32% of foliage consumption at the cotyledon stage, which surpassed economic thresholds but was not related to cultivar. Cabbage seedpod weevil (Ceutorhynchus obstrictus Marsham [Coleoptera, Curculionidae]) damage to canola pods ranged from 58 to 70 holes per 100 pods in 2001, and lygus plant bugs (Lygus spp. [Heteroptera, Miridae]) at the early pod stage reached densities of >37 individuals per 10 sweeps in 2000 and 2002. For both insect pests, their damage or abundance was similar among the conventional and HT cultivars. We conclude that, in the short term, the insect pests common in southern Alberta do not exhibit a preference to invade and damage the transgenic herbicide canola cultivars commonly planted in the prairies.