Cabbage stem weevil (Ceutorhynchus quadridens) on spring oilseed rape in Southern England and its control

Abstract

SUMMARYSurveys in 1974–75 in which 20 plants were examined in each of 105 fields showed that cabbage stem weevil was widespread on spring oilseed rape in the south of England, the larvae sometimes infesting a large percentage of plants and reducing vigour and yield. In replicated field trials during 1974–77, infestations were reduced by seed treatments of gamma‐HCH or sprays of gamma‐HCH, azinphos‐methyl, azinphos‐methyl + demeton‐S‐methyl sulphone, chlorpyrifos or triazophos. In some experiments treatments significantly improved plant growth or yield, or both. Granules of carbofuran or phorate also reduced larval infestations and damage, but both thiofanox granules and dimethoate sprays were ineffective. Sprays of gamma‐HCH or azinphos‐methyl + demeton‐S‐methyl sulphone which were effective against stem weevil could also in some years give improved control of blossom beetles (Meligethes spp.)