Abstract

The Hyblaea puera nucleopolyhedrovirus (HpNPV) is an ideal biocontrol agent for management of the teak defoliator, H. puera because of its host specificity, virulence and eco-friendly nature. However, application of HpNPV in extensive teak plantations is quite difficult owing to the rugged terrain of the plantation and height of the trees. The project was undertaken in the above context to develop a landscape level teak defoliator management strategy using the virus combining the knowledge on the population dynamics of the insect and the vertical transmission characteristics of the pathogen.

Vertical transmission of HpNPV (parent to offspring transmission) influencing different biological characters of the host was parameterized using a 76.81 kbp isolate of HpNPV under laboratory conditions. Infection of the fifth instar larva with a sub lethal dose of one hundred inclusion bodies of the virus revealed reduction in the survival of the larvae (20-40%), pupation (28%), adult emergence (27-66%), fecundity (50-78%), egg laying period (2 days), hatchability of the eggs (40%) but no change in the sex ratio. The reduction in reproductive potency due to vertically transmitted HpNPV from the parent to F1 generation inflicted collapse of the population in the F2 generation. This was further supported by sublethal dosing of HpNPV in a natural epicentre population in the Kariem-Muriem teak plantations, Nilambur, Kerala during March 2008 which also vertical transmission of HpNPV.

The trials on probable resistance of H. puera larvae to sublethal virus infection showed that the successive offspring generations were more susceptible to virus infection thereby ruling out the possibility of such a phenomenon in H. puera.

The results of this study indicated that one time low dose application of HpNPV during the epicentre phase of the teak defoliator population could contribute to the reduction in the insect population not only in the parent population but also in the F1 generation. This method of HpNPV application in the teak defoliator epicentres may be practiced for management of the teak defoliator at landscape level.