Seasonal prevalence and effect of abiotic factors on the invasive Eucalyptus gall wasp, Leptocybe invasa in North-Western India

Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is an invasive pest, native to Australia that cause serious damage in Eucalyptus (Myrtaceae). The present study was conducted to observe the seasonal variability of L. invasa on Eucalyptus tereticornis and effect of weather parameters on its incidence. Number of galls per meter branch length and gall wasp trapped on yellow sticky traps were counted at every two weeks interval during October 2019 to September 2021. In this study, mean number of galls per meter branch length was in the range of 2-14 and mean number of adults trapped ranged between 0-97 during both the years. Low incidence of L. invasa was observed during December to February as compared to March to November. Correlation and regression analysis was worked out for number of galls and adults trapped. Number of galls was recorded to be positively correlated with maximum temperature (0.397), whereas correlation was significantly negative with evening relative humidity (-0.466) and wind speed (-0.298). Number of adults exhibited significant positive correlation with maximum temperature (0.606) and minimum temperature (0.546). Significant correlation and regression values suggest that these weather parameters had influence on the number of galls and adults. Our results provided precise estimates in the period of incidence of L. invasa on Eucalyptus trees and correlation of weather parameters with gall wasp incidence. This study provides baseline data for future research in developing the pest forecasting system and eco-friendly module for integrated pest management.