Understanding the impact of host plant factors on the oviposition behaviour of the cabbage stem flea beetle (Psylliodes chrysocephala)

Abstract

For many phytophagous insects, oviposition plays a key role in the selection of an appropriate host. A more comprehensive understanding of the factors influencing this behaviour in pest insects provides a basis for the development of new management strategies. Herein, the determinants of oviposition were assessed in the cabbage stem flea beetle, Psylliodes chrysocephala (Coleoptera: Chrysomelidae), an insect specialized on the Brassicaceae family and a major pest of oilseed rape crops in Europe. To this end, a controlled condition experiment was conducted, in which a range of host plants exhibiting varying degrees of acceptability for feeding were presented to mature females. A superior host, Brassica rapa pekinensis, an intermediate one, Brassica napus, and a non-host plant, Iberis amara, were used. An additional treatment involved wrapping the plants in micro-perforated plastic bags to prevent feeding on aerial parts. The results demonstrated that contact with the host plant, and more particularly feeding, stimulated oviposition, with this effect being more pronounced in B. napus. Indeed, for the same amount of feeding, females laid significantly more eggs when feeding on B. napus than when feeding on B. rapa pekinensis. Additionally, a sequential experiment demonstrated that the intensity of oviposition is subject to rapid adaptive changes, as it is exclusively dependent on the current dietary conditions, with no influence of past dietary regimens. The quantification of macronutrients indicated the potential influence of plant-digestible carbohydrates on these outcomes. Further investigation is required to determine the impact of the plant nutritional quality and defences on oviposition.