Reports on gypsy moth management trials with LdMNPV baculovirus in Sardinian cork oak forest

Abstract: Cork oak protection against the action of Lepidopteran defoliators such as the gypsy moth Lymantria dispar requires an appropriate forest ecosystem management program, necessarily involving the application of eco-sustainable microbial products during insect population outbreaks. Species-specific baculovirus strains like the L. dispar multiple nucleopolyhedrovirus (LdMNPV), agent of natural epizootics in gypsy moth populations, may represent an option. Applications of industrially reproduced and formulated microbial products, are expected to achieve a significant gypsy moth biocontainment. The results of field trials assessing LdMNPV efficacy against L. dispar populations were conducted in 2018 and 2019 in Sardinia, according to a randomized block design. Each year, two trials were conducted applying a baculovirus commercial formulation with atomizer from ground and assessing the effects of different doses and application timing, respectively. In both years, a significant increase in larval mortality was detected in plots treated with higher viral occlusion body (OB) concentrations and with an earlier application targeting younger larvae, in comparison with untreated controls. An aerial application trial distributing LdMNPV at ultra-low volumes (2 l/ha) was also conducted in 2019, to assess the virus efficacy at a larger field scale. While no significant differences in larval density between treated and control areas were detectable in such conditions in the few weeks following application, a meaningful vitality decrease in larval samples from treated plots was observed. As a result of LdMNPV application, additional effects on the next gypsy moth generation are expected.