BIOLOGY AND LARVAL MORPHOLOGY OFCEUTORHYNCHUS NEGLECTUS(COLEOPTERA: CURCULIONIDAE), A MINOR PEST OF CANOLA (BRASSICACEAE) IN WESTERN CANADA

Abstract

AbstractA study was undertaken to determine aspects of the life history, behaviour, and host plant feeding preferences ofCeutorhynchus neglectusBlatchley, a minor pest of canola,Brassica napusL. andBrassica rapaL., in western Canada. The final-instar larva was described for the first time.Ceutorhynchus neglectuswas univoltine, with adults first occurring on host plants in early June. Mating occurred throughout June and July, and eggs were laid into the distal ends of developing siliques of flixweed,Descurainia sophia(L.) Webb (Brassicaceae). Mate guarding behaviour was observed for males ofC. neglectus, which remained attached to females long after copulation was completed and, if necessary, struggled with rival males to prevent them from fertilizing their mates. Larvae fed upon developing seeds and, when mature, bored through the pods, dropped to the soil, and constructed earthen cells approximately 2 cm beneath the soil surface where they pupated. Results from laboratory host preference studies were consistent with field observations which indicated that among selected species of Brassicaceae, leaves and siliques ofD. sophiawere preferred by adults ofC. neglectusas feeding sites. In contrast to flea beetles,Phyllotreta cruciferae(Goeze) (Coleoptera: Chrysomelidae), which fed indiscriminantly over the entire cotyledon surfaces of canola seedlings, adults ofC. neglectuscaused less cotyledon damage per individual and tended to feed on cotyledon edges. Because of its biology and host plant preferences,C. neglectusshould remain a minor pest of canola, and can only be expected to invade the crop when its preferred host (flixweed) is unavailable.