Role of soil and larval excreta in the horizontal transmission of the baculovirus HpNPV and its implications in the management of teak defoliator Hyblaea puera

In baculovirus–insect systems, a mixed-mode transmission strategy involving vertical transmission of virus from parent to offspring, and horizontal transmission from infected to susceptible or from the environment is well known. In this study, we examined the role of soil and excreta as alternative routes of horizontal transmission of Hyblaea puera nucleopolyhedrovirus (HpNPV) in the teak defoliator H. puera and how larval crowding influences these processes. The laboratory experiment failed to identify horizontal transmission of the virus from the soil during pupation or eclosion. However, the role of soil as a reservoir cannot be ignored as chances of transport of viral particles from soil to tree bark are expected through termite nests built on teak stems, which needs further examination. On the other hand, the experiments proved excreta as a major route of horizontal transmission and the rate of infectivity during crowding of larvae was significantly higher. Further research on other routes of horizontal transmission and host behaviour influencing the same are discussed here in the context of their role in managing of teak defoliator outbreaks