Spatial-temporal trends in insecticide resistance: What have we learned?

Monitoring is an important part of insecticide resistance management (IRM) plans and can provide timely information for growers to select the most effective insecticide chemistries. Our project goal was to develop a national insecticide resistance monitoring network to evaluate both neonicotinoid resistance and the susceptibility of Colorado potato beetle (CPB) to a number of alternatives in 3 other insecticide classes. We hypothesized variations in susceptibility may be due to regional differences among CPB populations in their expression of genes, altering their ability to detoxify and/or metabolize other insecticide active compounds. Such differences may in turn be associated with the intensity of past use of neonicotinoids. In Manitoba and Ontario, there was greater resistance to neonicotinoids and anthranilic diamides (the 2nd most commonly used insecticides). Regions where fewer applications of thiamethoxam and clothianidin occurred during that period indicated fewer incidences of resistance or reduced susceptibility. Over the 5 year period, no significant change in neonicotinoid susceptibility was observed within all regions, but cross-resistance with diamides was noted in several cases. By providing in-season resistance survey data in each region through an interactive online map and molecular diagnostic resistance assessment, we aim to provide growers improved resistance detection tools in future.