Sustainable production of mahogany in plantations: Biology of mahogany shoot borer (Hypsipyla robusta Moore) on artificial media and associated natural enemies

Hypsipyla robusta (Moore) Lepidoptera: Pyralidae is a major pest of meliaceous forest trees, especially mahogany, and hampers efforts at establishing mahogany plantations. The larvae of H. robusta destroy the principal terminal shoot by boring into the tips and tunneling in the stems of young saplings causing branching, stunted growth, and tip death. In an attempt to contribute to finding a solution to the problem, larvae were sampled from the field, the life cycle (biology) of H. robusta was studied on artificial media, and an amended diet with mahogany plant tissues. The natural enemies associated with the insects sampled from the field were also isolated and identified. The number of H. robusta larvae differed significantly between sampling periods and the maximum coincided with the peak of the rainy season and flushing of new shoots. Ventilated breeding cages with mahogany plant tissue or amended diet produced the highest values for all the parameters related to rearing success in the lab. The average minimum and maximum days of the life cycle of H. robusta (egg to adult) were 39 days and 51 days respectively. Oviposition took place for 1-3 days and the incubation period lasted between 3 to 4 days. The larval development period takes five to seven instars, and the days to complete larval development was 20-34 days for larvae going through five instars, 27-41 days for larvae going through six instars, and 30-46 days for larvae going through seven instars, and pupation lasted for 7-10 days. Six parasitoids, belonging to two insect orders Hymenoptera and Diptera, and the nematode Hexamermis sp were isolated from the larvae and eggs. Four pathogenic fungal species belonging to two genera, Beauvaria and Fusarium, were also isolated. The findings from these studies of Hypsipyla biology, in addition to parasitoids and fungal pathogens identified as biocontrol agents, could contribute to the efforts towards Integrated Pest Management of H. robusta