Capsids (Heteroptera, Miridae) in strawberries, and their influence on fruit malformation

SummaryField investigations in Southern Norway in 1968 and 1969 showed capsids to be the main cause of strawberry fruit malformation. The predominant species Plagiognathus arbustorum Fabr. oviposited in the autumn at the base of the outer leaf stalks of the strawberry plants. The eggs hatched at the beginning of the flowering period, and the first adults appeared shortly before first harvest. In cage experiments 4 larvae per inflorescence caused 94% fruit malformation. The symptoms from feeding in open flowers were strikingly different from those caused by feeding on young fruits. In laboratory preference tests, adult P. arbustorum preferred flowers and fruits and were not observed feeding on leaves.Lygus rugulipennis Popp. was the second most important species. Severe fruit damage occurred in cage experiments. In preference tests L. rugulipennis strongly preferred flowers and flower buds and oviposited in the calyx or flower stalk.Plagiognathus chrysanthemi Wlff. and Calocoris norvegicus Gmel. were found in only a few fields.The types of malformation caused by capsids could be fairly accurately assessed in the field. Attacks were accompanied by little or no leaf damage. Most capsids and fruit malformation were found in weedy fields and in fields where no insecticides were used.