Effect of Adult Nutrition at Different Concentrations on Reproduction and Longevity of <i>Bracon brevicornis</i>, Larval Parasitoid of Coconut Black-Headed Caterpillar

Abstract

Coconut black-headed caterpillar (Opisina arenosella) or BHC is one of the main coconut palm defoliators in many Asian countries, including Malaysia, where it was discovered in 2017. Since then, an effort has been made to manage the pest by the use of larval parasitoids, started with a study on the effects of sucrose diet on reproduction, longevity and parasitism of a naturally occurring parasitoid known as Bracon brevicornis (Hymenoptera: Braconidae). The aim of this study was to determine the optimal sucrose concentration for improving its rearing technique. Two experiments were conducted, i.e., a) reproductive performance study; and b) longevity study. In each study, different sucrose concentrations were tested on mated females in five (5) replications. Feeding on 20% sucrose concentration resulted in significantly (P<0.05) highest fecundity (82.4 ± 0.9), hatchability (100%), pupation, fertility (82.7%) and longest reproductive period (12.8 ± 0.3 days) of B. brevicornis among treatments. Meanwhile, 40% sucrose was able to prolong its adults' lifespan (20.6 days). Adults fed on 20% sucrose had the highest parasitism (33.4±0.6 host larvae), despite the fact that 30% sucrose had no statistically significant difference. Thus, this study suggested that 20% sucrose could be suitable to increase fertility and parasitism by B. brevicornis. However, additional research on its effect on behaviours is necessary to acquire a better knowledge of its efficiency in the field.