Biological Studies and Chemical Control of Brown Scale (Parthenolecanium corni (Bouché)) on Red Currant

Abstract

SUMMARYIn 1972 and 1973 biological observations were made on brown scales infesting red currant bushes in a plantation in Kent. Scales matured between the end of May and the second week of June, eggs were first found at the end of June and larvae hatched during the first week of August each year; these times are about one month later than previously recorded. Up to 2,011 eggs were found under a single mature scale. In chemical control tests in the same plantation, tar oil winter wash gave good control of the pest; lime sulphur winter wash was less effective but reduced the numbers of scales significantly. Spring application of dimethoate, Fenitrothion or malathion killed most overwintered scales, but endosulfan was ineffective. Suspensions of malathion, dimethoate, diazinon, fenitrothion, demeton‐S‐methyl, dichlorvos, tar oil or lime sulphur killed 92–100 per cent of larvae on the foliage.