The Impact of the Carrot Rust Fly and Carrot Weevil Integrated Pest Management Program on the Ground-Dwelling Beetle Complex in Commercial Carrot Fields at the Holland Marsh, Ontario, Canada

Carrot rust fly (CRF), Psila rosae (Fabricius, 1794) (Psilidae: Diptera) and carrot weevil (CW), Listronotus oregonensis (Le Conte, 1857) (Curculionidae: Coleoptera) are economic pests of carrot; larval tunneling on roots results in direct damage rendering the carrot unmarketable.The Holland Marsh in Ontario, Canada, is a major carrot production area. The ground-dwelling beetle (Coleoptera) fauna in commercial carrot fields in this region has not been described. In 2015 and 2016, eight commercial carrot fields were surveyed using pitfall traps to determine abundance and diversity of the ground-dwelling beetle complex. Research sites, which were used to evaluate the effectiveness of an existing integrated pest management (IPM) program, were also surveyed to determine the impacts of the IPM program on the natural enemy diversity, compared to insecticide-free sites. In total, 50 taxa and 4,127 individual ground-dwelling beetles were identified over the course of the 2 y. Known natural enemies of CRF and CW were identified and recovered in abundance. The abundance and diversity of ground-dwelling beetles among the commercial carrot fields varied greatly in 2015 and 2016 but was similar on research sites sprayed according to the IPM program compared to insecticide-free sites in both years. The importance of this research to promote conservation biological control through the naturalization of nonagricultural areas is discussed.