Development of Galls in Eucalyptus Due to Infestation of Leptocybe invasa and Its Effects on Growth of Seedlings.

Abstract

Leptocybe invasa Fisher & LaSalle (Hymenoptera : Eulophidae), commonly known as blue gum chalcid wasp, is a major gall making insect species of eucalyptus, causing serious damage to seedlings in nursery stage. An insectary/nursery of eucalyptus was developed at this Institute to study the stages of gall development, number of galls formed with the age of seedling and effects of galls on the growth of seedling. Results revealed that there are five distinct stages of gall development, first stage initiates by the insertion of eggs on the epidermis of soft young leaves, petioles and stems and final stage ends with the emergence of adult wasps from galls through exit holes. It was observed that the development of galls start after one month age of seedlings, and there was significant (P<0.05-P<0.01) variation in growth (height and collar diameter), number of galls in leaves, petioles and stems, and total number of galls/seedling in respect of age. The data clearly exhibited that one month old seedlings were free from the attack of L. invasa as because there was complete absence of galls. Further, it was recorded that seedlings growth (height and collar diameter) was affected by the development of galls, minimum growth was recorded in case of maximum galls developed whereas less galls were noticed for maximum growth of seedlings. There was an inverse relationship exists between seedling growth and development of galls. The practical application of findings was discussed in the light of the present observations.