Influence of virus inoculation method and host larval age on productivity of the nucleopolyhedrovirus of the teak defoliator, Hyblaea puera (Cramer)

Hyblaea puera nucleopolyhedrovirus (HpNPV) is a potential biocontrol agent against the teak defoliator H. puera (Cramer) (Lepidoptera: Hyblaeidae). As part of optimization of the mass production of this nucleopolyhedrovirus, three methods of inoculation were evaluated against the host larvae with various yield parameters as selection criteria. The inoculation methods compared were controlled dose on diet in rearing tubes using a micropipette, controlled dose on leaf discs (prepared from teak leaves) using a micropipette and spraying onto diet filled rearing tubes using an atomizer. Fifth instar H. puera larvae of the weight classes 75–100, 101–125, 126–150, 151–175 and 176–200 mg were used for the bioassay. With reference to percentage of harvested larvae, virus production per larva and virus production per inoculated larva (VPIL), spraying viral suspension into rearing tubes filled with artificial diet using a hand sprayer was found to be the most efficient method of inoculation. It was observed that the method of inoculation and age of the larvae has discrete as well as interactive influence on the virus yield parameters.