Responses of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), to seed treatments of canola (Brassica napus L.) with the neonicotinoid compounds clothianidin and imidacloprid.
BACKGROUND
The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a major pest in the production of canola (Brassica napus L.) in North America and Europe, and effective population control is often essential for economical crop production. In North America, neonicotinoid insecticides have been used for several years in canola as seed treatments for reducing herbivory by flea beetles. The neonicotinoids clothianidin and imidacloprid were investigated to determine their effects on preimaginal development and on emergence of new-generation adults of C. obstrictus in comparison with effects of lindane, a chlorinated hydrocarbon seed treatment.


RESULTS
Mean numbers of second- and third-instar larvae were significantly higher in plants seed-treated with lindane than in plants treated with the neonicotinoid compounds, even though weevil oviposition was similar for all treatments. Emergence of new-generation adults was reduced by 52 and 39% for plants seed-treated with clothianidin and imidacloprid, respectively, compared with emergence from plants treated with lindane.


CONCLUSIONS
Seed treatment with both clothianidin and imidacloprid produced systemic insecticidal effects on larvae of C. obstrictus, with clothianidin slightly more effective than imidacloprid. Use of clothianidin or imidacloprid as seed treatments can comprise an important component in the integrated management of cabbage seedpod weevil in canola.
Dosdall
Lloyd M
LM
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada. lloyd.dosdall@ualberta.ca
D000818:Animals; D029688:Brassica napus / Q000187:drug effects / Q000469:parasitology*; D006146:Guanidines / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology*; D007300:Insect Control / Q000379:methods*; D007306:Insecticides / Q000494:pharmacology*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology*; D010058:Oviposition / Q000187:drug effects; D010935:Plant Diseases / Q000469:parasitology; D012639:Seeds / Q000187:drug effects / Q000469:parasitology*; D013844:Thiazoles / Q000494:pharmacology*; D048889:Weevils / Q000187:drug effects* / Q000502:physiology
D006146:Guanidines; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D013844:Thiazoles; C480342:clothianidin; C082359:imidacloprid