Notes on Diconocoris hewetti (Dist.) (Hemiptera: Tingidae) a pest of pepper in Sarawak (Malaysian Borneo)

Abstract

An account is given of Diconocoris hewetti (Dist.), a sporadic pest of pepper in Sarawak. Most of the observations were made during a single outbreak in 1964. The egg and the five nymphal stages are described. The life cycle is completed in about 30 days at 27 ± 1°C., 80 ± 2 per cent. R.H. and the duration of individual stages is as follows: egg, at least ten days; first instar, four days; second instar, three days; third instar, three days; fourth instar, four days; fifth instar, five days; adults in laboratory cultures lived, on average, for 27 days.Eggs are laid singly in the flowering inflorescences, and nymphs do not generally move far from their hatching sites during nymphal life. Both nymphs and adults feed on the inflorescences and infestation is particularly heavy on those spikes in which fertilisation of the flowers has ocurred but where the developing fruits do not yet exceed 1 or 2 mm. in diameter.A survey of 60 holdings in the Kuching area showed that numbers of Tingids are very low during non-outbreak periods, only 0.4 individuals per vine (adults and late nymphal instars) being obtained during the flowering season. Numbers deceased to 0.03 insects per vine during the fruiting period. In the outbreak studied, numbers per vine varied from 3 to 10, a ten- to one hundred-fold increase over the normal levels; these figures are relative estimates only as there was no satisfactory method of estimating absolute densities in the time available.It is suggested that serious outbreaks of Diconocoris may be due to exceptional prolongation of the flowering period of pepper vines in a district, due to cultural practices or climatic factors.Yield losses due to Tingids in the area studied were estimated at about 30 per cent. Diconocoris can be satisfactorily controlled with sprays of various insecticides including BHC, DDT, malathion, carbaryl (Sevin) and nicotine.