Field evaluation of Lymantria obfuscata multiple nucleopolyhedrovirus for the management of Indian gypsy moth in Jammu & Kashmir, India

• NPV exists in the natural populations of Lymantria obfuscata.
• The NPV was isolated from the L. obfuscata larvae and successfully applied in crude form as a bio-pesticide in the field.
• The field application of the NPV with the dosage of 2.5 × 1012 OBs/ha reduced the larval population density by 25–63%.
• It was found that the NPV was recycled and persisted in sprayed areas after initial application.
• The application of NPV on the wild hosts could help to prevent population outbreaks and population dispersal to crops.

The Indian gypsy moth (Lymantria obfuscata) is a pest of national significance, which attacks a wide range of forest and fruit crops in India. The outbreaks of this pest over the past few years spurred interest towards sustainable biointensive approaches for quality fruit production of apple and walnut for agricultural export in Jammu & Kashmir (J & K). The exploratory survey's were conducted for the isolation of native strains of L. obfuscata multiple nucleopolyhedrovirus (LyobMNPV) and field evaluation was conducted to determine the most promising strain as a potential biological control agent of this pest. The virus was recovered from different locations of J&K with its natural incidence varying from 0.77 to 7.43 percent. This is the first report from the Indian sub-continent and worldwide of the occurrence of NPVs in natural larval populations of L. obfuscata. The in vivo mass production was optimised by inoculating per os late 3rd instar L. obfuscata larvae with an inoculum dose of 1.44 × 105 OBs/larva and followed by a 10 day incubation period. To prevent the disintegration of larval cuticle and microbial contamination, moribund larvae were harvested with an average yield of 1.42 × 108 OBs/larva. The field application of LyobMNPV against the host populations on apple and willow with the pre-standardised dosage of 2.5 × 1012 OBs/ha reduced the larval population density by 25–63%. In the year following application, the larval population density in the treated blocks was 19–28% lower as compared to controls on both apple and willow. This suggests that the virus has considerable potential as a biocontrol agent and the timely application with LyobMNPV on non-fruit trees such as willow which are the preferred hosts for egg laying may help to initiate viral epizootics to keep population outbreaks under check.