Biological control agents against the cabbage stem flea beetle in oilseed rape crops

Abstract

The cabbage stem flea beetle (CSFB11CSFB: cabbage stem flea beetle.) Psylliodes chrysocephala Linnaeus is the most important pest of oilseed rape (Brassica napus) crops in Europe. Control has become more difficult since the European Union ban in 2013 on the use of neonicotinoid seed treatments. This situation is made more challenging by the development of resistance to pyrethroid insecticides, the only remaining conventional synthetic insecticides with which to control CSFB.The purpose of this paper is to review the potential of biological alternatives to the use of synthetic pesticides for the control of the CSFB. Only a small number of studies have investigated biological control agents against CSFB itself. More research has, however, been published on two other, closely related chrysomelid pests of brassica crops that have similar life cycles, namely the crucifer flea beetle Phyllotreta cruciferae and the striped flea beetle Phyllotreta striolata, which enable us to extrapolate reasonably across to CSFB. The biological control agents investigated include entomopathogenic fungi (EPF22EPF: entomopathogenic fungi.) such as Metarhizium anisopliae and Beauveria bassiana, entomopathogenic nematodes (EPN33EPN: entomopathogenic nematode.) such as Steinernema feltiae and Steinernema carpocapsae, parasitoids such as Microctonus brassicae and predators such as the ground beetle Trechus quadristriatus. Results vary depending on the setting (laboratory versus field), but several biological control agents investigated resulted in CSFB mortality greater than 50% under laboratory conditions. The biological control of the CSFB shows potential as a viable alternative to the use of conventional synthetic insecticides. Nonetheless, many research gaps remain, as current research has focused largely on crucifer flea beetle and striped flea beetle, with comparatively few studies investigating the potential of biological controls against the CSFB. The research published to date on CSFB has been limited to a small number of species of EPN and EPF with little work investigating the potential of parasitoids and predators. More field studies using EPF are required, while in contrast laboratory studies are underrepresented for EPN.Further research is required, testing existing and new strains of fungi and nematodes, exploring the potential of endophytic fungi, enhancing the formulation and application of biological control for use in inundative strategies, and investigating the potential of conservation biological control. Effective biological control agents should ultimately be combined with cultural control methods in Integrated Pest Management (IPM44IPM: Integrated Pest Management.) systems for the sustainable management of this pest.