Efficacy of diamide, neonicotinoid, pyrethroid, and phenyl pyrazole insecticide seed treatments for controlling the sugar beet wireworm, Limonius californicus (Coleoptera: Elateridae), in spring wheat

Four classes of insecticide applied on seed were evaluated for managing high populations of the sugar beet wireworm, Limonius californicus (Coleoptera: Elateridae), in spring wheat in southern Alberta, Canada. Three separate field trials were conducted, and assessments made for stand protection, yield, and wireworm survival. Imidacloprid and thiamethoxam applied at 10–30 g AI and cyantraniliprole applied at 10–40 g AI provided initial stand protection, but did not protect seedlings until harvest and did not decrease wireworm populations. λ-cyhalothrin applied at 30 g AI provided stand protection that persisted until harvest, but yields were considerably lower than observed in fipronil treatments and there was little (23%) decrease in populations relative to controls. Fipronil applied at 0.6, 1.0, and 5.0 g AI, either singly or in blend with thiamethoxam at 10 g AI, provided stand protection until harvest and significantly reduced numbers of wireworms larger than 10 mm (range: 74–96%). Very low numbers of small (<11 mm) wireworms were observed in all trials. These results are compared to data from laboratory and field studies for this and other wireworm species. The relation between crop stand protection and wireworm mortality, the potential of insecticide blends, and the importance of seed type, wireworm species, and activity periods for managing wireworms with seed treatments are discussed