Comparative biology of Leptocybe invasa (Hymenoptera: Eulophidae) in green and pink galls on Eucalyptus in North Western India

Abstract

Abstract Leptocybe invasa Fisher & La Salle is an invasive pest, native to Australia, causing heavy damage in Eucalyptus nurseries and plantations throughout the world.Biology of L. invasa on Eucalyptus was studied during 2020-2021 at Ludhiana, Punjab. To study the biology throughout the year, leaf samples were tagged four times on 15 March, 15 June, 15 September and 15 December. Adult emergence was observed from two types of galls viz., pink and green-coloured galls during summer months and from pink coloured galls during winter months. When adults emerged from pink-coloured galls, the life cycle was completed in 115-150 days consisting of five stages of gall development viz. Stage 1 (Tissue disruption), Stage 2 (Gall development), Stage 3 (Glossy pink), Stage 4 (Dull pink) and Stage 5 (Exit hole). During summer months, life cycle of L. invasa was completed in 115-119 days when adults emerged from pink coloured galls. However, life cycle of L. invasa was extended in winter season due to hibernation in larval and pupal stage and life cycle was completed in 150 days. Additionally, adult emergence was also observed from green galls during summer months and life cycle of L. invasa was completed in 86-89 days. Further, when adults emerged from green coloured galls in summer months, stage 3 and stage 4 were not observed. Adult longevity was significantly higher when adults were fed on honey water solution (6.16 days) followed by only water (4.56 days) and young Eucalyptusleaves (3.62 days). However, adult longevity was lowest when kept without food (3.16 days). Gall width ranges between 2.76-2.91 mm and gall length ranged from 5.22-5.32 mm. Shape of galls was bump shaped. So, in current study we recorded time taken for completion of L. invasa life cycle varied with respect to season and total life cycle of L. invasa was completed in 86-150 days depending upon the season. In winter season the larva and pupa hibernated extending the life cycle of L. invasaduring cold months. There is immense potential for rapid population build-up of L. invasa over multiple generations in a year.