Project code: MU03-ENT1
Bob Vernon - Agriculture and Agri-Food Canada
To evaluate lower-risk alternative insecticides under field conditions for efficacy in controlling wireworms in potato crops and to develop bioassays for evaluation of new, untested insecticides
Summary of Results
Wireworms, the larval stage of various species of click beetles (Coleoptera: Elateridae), are serious pests of a wide variety of crops world-wide. Subterranean feeding by wireworms can result in catastrophic crop losses due to stand and yield reduction in cereals, corn and vegetables and/or cosmetic injury in carrots and potato. In Canada, several endemic species of wireworms and three exotic European species are increasing in severity in many crops, the greatest impact being on potato in many key growing regions. Prior to the advent of synthetic insecticides, potato production was not possible in parts of Canada due to chronic wireworm damage. With most of the most effective wireworm insecticides now virtually obsolete in Canada, the impact of wireworms on susceptible crops is again growing, and this is especially true in British Columbia (BC) and Atlantic Canada where three highly destructive exotic European species have now become dominant.
A major objective of the project was to develop laboratory bioassays and field trial protocols that would determine the long-term and short-term toxic (i.e., sub-lethal and lethal) and/or behavioural (i.e., attractive and repulsive) effects of any candidate insecticide or combinations thereof on any species of wireworm in Canada. This objective was met with the development of various unique laboratory LC50, LD50, and LT50 protocols, and behavioural bioassays to study the toxic, repulsive and attractive effects of insecticides on wireworms in a simulated soil environment. Field protocols were also developed to discern the efficacy of insecticides in terms of: a) protection of daughter tubers at harvest; and b) the actual toxic effects of insecticides on wireworm populations in the field. Field trials were successfully conducted at AAFC Agassiz (BC), London (ON), Kentville (NS) and Charlottetown (PE). Together, the laboratory and field studies uncovered several previously unknown toxic (i.e., long-term latent mortality and long-term intoxication) and non-toxic effects (repulsion) of many insecticide classes on wireworms. These findings gained the study worldwide recognition and have led to the development of an attract-and-kill strategy using insecticide at rates that would pose negligible risk to human health or the environment but which yield crop protection equivalent or better than the current , higher risk standard Thimet 15G. The development of these strategies is the focus of another project, MUR06-310. As a result of data generated in this project, Minor Use registrations were obtained for chlorpyrifos (Pyrifos 15G and Pyrinex 480EC) in 2006, and a registration package for clothianidin (Poncho 600F) was submitted to the federal regulator in 2007. It is anticipated that a registration submission for thiamethoxam based on data generated under this project will also be made in 2007.
Given the variable susceptibility of the various wireworm species to different insecticides, a network of scientists and field personnel has been established to monitor wireworm populations in agricultural areas across Canada and to assist in the development of site-specific wireworm IPM recommendations in the future.