FLEA BEETLE (COLEOPTERA, CHRYSOMELIDAE) RESPONSE, FEEDING, AND LONGEVITY ON OILSEED RAPE AND CRAMBE

Cage environments in the laboratory were used to study flea beetle, Phyllotreta cruciferae (Goeze), feeding, response, and longevity on oilseed rape (Brassica napus L.) and crambe (Crambe abyssinica Hochst.). Flea beetle feeding occurred almost exclusively in the light. Flea beetles fed significantly more on oilseed rape than on crambe in choice and no-choice tests. Residence time on oilseed rape also was longer. In choice tests, there was no difference in transition frequency between oilseed rape and crambe. In no-choice tests, significantly higher transition frequency was observed on crambe. Mechanical wounding of the cotyledons of the two plant species did not influence flea beetle response or feeding. The effect of flea beetle density on the amount of feeding was described with a second-order polynomial regression, which suggests that the beetles need to aggregate in sufficient numbers to utilize a host optimally. In the long-term feeding studies, the amount of feeding per beetle differed significantly between oilseed rape and crambe during the initial 25 d, after which there were no significant differences. Flea beetles that fed on oilseed rape lived significantly longer than those that fed on crambe. There was no difference in longevity between males and females fed on the same plant materials. The results confirm that crambe is a less-suitable host for flea beetles than is oilseed rape.