Abstract

A serious disease of the teak defoliator Hyblaea puera caused by a nuclear polyhedral virus was observed in various teak plantations. Bioassay studies revealed that the virus is highly pathogenic to H. puera. Median lethal concentration and median lethal dose values were 796 PIB/mI and 1427 PIB/larva respectively. Median lethal time values increased with reduced concentrations/doses. Nearly 35 percent infectivity was lost due to exposure to UV light of ca. 250 nm for 15 min at 10 cm distance from the UV source. Heating the virus at 40 degree C for seven days did not markedly reduce infectivity. Less than 10 inactivation occurred when virus was held at pH4 and 9. 2 for 6h. There was no cross infectivity to larvae of three other forest insects. A fourth instar larva yielded mean of 38. 72 +-10. 75 X 10. PIB and the productivity ratio was 5530. Three species of bacterial pathogens, viz., Bacillus cereus, B. thuringiensis var. thuringiensis, and Enterobacter aerogenes were also