REARING OF FIELD COLLECTED LARVAE OF THE MAHOGANY SHOOT
BORER, Hypsipyla robusta (MOORE) ON AN ARTIFICIAL DIET: A PRELIMINARY
Rizana M Mahroof*, Jayanthi P Edirisinghe* and Caroline Hauxwell**
* University of Peradeniya; ** Institute of Ecology and
Resource Management, University of Edinburgh
Hypsipyla robusta (Morre) (Lepidoptera: Pyralidae) is an important pest
of mahogany, Swietenia macrophylla (King) in Sri Lanka and world over.
Larval attack at an early stage 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 and development of mahogany and
attack by the shoot borer. This paper presents aspects of development
of shoot borer larvae reared on an artificial diet, as well as field information
related to damage and parasitism. Larvae collected from two field sites
at fortnight intervals were reared in the laboratory on an artificial
diet at 27-320 C. Development of field collected larvae were followed
until the emergence of adults, during which duration of the 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 of which 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 different
parts of the growing shoot. Duration of development of larvae differed
depending on whether they were parasitized or not. Several problems encountered
during rearing are discussed.
Department of Forestry and Environmental Science,
of Sri Jayewardenepura,Sri Lanka. 1999. All rights reserved.