REARING OF FIELD COLLECTED LARVAE OF THE MAHOGANY SHOOT BORER, Hypsipyla robusta (MOORE) ON AN ARTIFICIAL DIET A PRELIMINARY STUDY

Abstract

Hypsipyla robusta (Morre) (Lepidoptera: Pyralidae) is an important pest of mahogany,Swietenia macrophylla (King) in Sri Lanka and world over. Larval attack at an earlystage of growth, leads to branching which reduces the quality and value of timber,significantly. Work is in progress to study the effect of shade on the growth anddevelopment of mahogany and attack by the shoot borer. This paper presents aspects ofdevelopment of shoot borer larvae reared on an artificial diet, as well as field informationrelated to damage and parasitism. Larvae collected from two field sites at fortnightintervals were reared in the laboratory on an artificial diet at 27-32° C. Development offield collected larvae were followed until the emergence of adults, during which duration ofthe developmental stages, adult sex ratio, parasitism level and mortality were recorded.Measurement of head capsule widths of larvae collected and their location on the shoot,was also made. A total of 774 larvae were collected and reared during the study, out ofwhich 120 Hypsipyla adults emerged giving a male: female sex ratio of 1:8. Nearly 40%of the field collected larvae were parasitized by Cotesia app. (Hymenoptera: Braconidae).Head capsule measurements indicated five larval instars that were found to infest differentparts of the growing shoot. Duration of development of larvae differed depending onwhether they were parasitized or not. Several problems encountered during rearing arediscussed.