Deposition and longevity of oviposition-deterring pheromone in the cabbage seed weevil

The cabbage seed weevil (Ceutorhynchus assimilis Payk.) lays eggs singly into pods of oilseed rape (Brassica napus L.) through punctures bored with the mouthparts, preferring pods not recently used for oviposition. A simple new choice test has been used to test individual components of egg-laying behaviour for their effect on oviposition site selection. It is confirmed that an oviposition-deterring pheromone (ODP) is deposited during abdomen brushing of the pod which follows egg-laying. Neither pin punctures, weevil feeding punctures, oviposition punctures nor eggs had any deterrent effect. Pods walked on by female weevils were not avoided by those laying eggs. Observations suggest that the ODP is sensed by contact chemoreceptors on the antennae. The deterrent effect lasted only 1-2 h. The implications of these findings on the adaptive significance of the pheromone and its possible use in pest control are discussed.