Insecticide resistance and cross‐resistance development in Colorado potato beetle Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) populations in Canada 2008–2011

BACKGROUND A survey of insecticide resistance in over 150 Canadian populations of Colorado potato beetle was completed between 2008 and 2011. Three neonicotinoid and two anthranilic diamide insecticides were tested at a discriminating concentration ( DC ) with second‐instar larvae in a leaf‐disc bioassay. RESULTS The mean mortality for the imidacloprid (Admire) DC was 46–67% between 2008 and 2011 respectively. Over the 4 years, 10–46% and 26–40% of the populations were classified as resistant or showed reduced susceptibility to imidacloprid. The mean mortality for thiamethoxam (Actara) and clothianidin (Poncho/Titan) ranged from 56–76% in 2008 to 81–84% in 2010 for each insecticide respectively, indicating continuous susceptibility to clothianidin but reduced susceptibility to thiamethoxam. In 2008 and 2009, susceptibility to chlorantraniliprole (Coragen) was observed in 85% of populations. Similarly, cyantraniliprole (Cyazypyr) affected 93% of the 2009 and 74% of the 2010 populations. There was a significant ( P < 0.05) and high positive correlation ( R = 0.4–0.84) between the three neonicotinoids, indicating the potential for cross‐resistance. CONCLUSIONS The trend observed in decreasing susceptibility for thiamethoxam and clothianidin will continue unless resistance management practices are followed. © 2014 Her Majesty the Queen in Right of Canada Pest Management Science © 2014 Society of Chemical Industry