Insect injury to linseed in south-east England

Abstract

Pests were monitored on linseed crops in Hertfordshire, Cambridgeshire and Bedfordshire from 1987 to 1990. Adult flea beetles (Aphthona euphorbiae and Longitarsus parvulus) caused severe injury to seedlings; their numbers have markedly increased since 1990 and they are now important pests of linseed in the UK. Two generations of Thrips angusticeps bred on linseed, causing damage to growing points and flower buds and approximately 14% yield loss to a crop in Hampshire. Mirids, mostly Calocoris norvegicus and Lygus rugulipennis, caused injury similar to that caused by thrips. Mirids were more abundant close to field boundaries with woody plants, whereas thrips were fewer at these boundaries and rather evenly distributed within the rest of the field. Few other insects and no aphid colonies were found. Experiments with insecticide treatments provided evidence of compensation for insect injury by additional flower production. (C) 1997 Elsevier Science Ltd.