Abstract

This project in Kerala evaluated the usefulness of a naturally occurring nuclear polyhedrosis virus of the teak [Tectona grandis] defoliator Hyblaea puera (HpNPV) and developed suitable field application methods. The HpNPV was confirmed as belongingto the family Baculoviridae, and electrophoretic analysis of its DNA using restriction endonucleases showed its similarity to other insect NPVs. Cross infectivity studies showed that the HpNPV was highly host-specific, and therefore, safe for field application. Epizootiological studies showed that it had little environmental persistence (not even a week on teak foliage). Disease transmission studies indicated intra-host persistence and transovarian transmission from the second filial generation under controlled laboratory conditions. These results indicated that it would not be possible to induce disease epizootics under field conditions by enhancing the inoculum load in the environment artificially. An inundative spray of polyhedra during an infestation was, therefore, concluded to be the only possible control option. In the field trial carried out in 1993, repeated infestations by H. puera in a 100-tree plot were controlled by timely application of HpNPV during each outbreak; 70-76 of the foliage loss caused by the pest was prevented by application of a high-volume spray (0.75-1.75 litres/tree) containing 1X105 PIB/ml. A unique mass production method was developed for HpNPV, which made use of the availability of large numbers of larvae during natural pest outbreaks in teak plantations. Laboratory methods of HpNPV production were also developed using artificially reared larvae. Methods were standardized for timely application of HpNPV using a pest monitoring system involving moth catches with a solar powered light trap