Spatial distribution of the blue gum chalcid, leptocybe invasa on eucalyptus species in Kenya.

Abstract

Blue gum chalcid (BGe), Leptocybe invasa is a gall-forming wasp, which causes an extensive damage to Eucalyptus. It attacks mostly seedlings and field saplings. It causes damage on its host by forming massive typical bump-:shaped galls on tree canopy, specifically on the leaf midribs, petioles and stems of new growths. Repeated attacks leads to twisted and knobbed appearance of the leaves and terminal leader shoot degenerates into lateral shoot. The objective of this study was to determine the spatial distribution of BGC damage incidence and severity patterns in Kenya. A total of 155 selected stands from five major Eucalyptus growing provinces were assessed. Three randomly established plots per stand consisting of 20 trees were assessed for BGC damage severity on a 4-point scale. This was used to determine the mean severity patterns. All descriptive statistics were analysed using percentage damage score. Mean damage score were analysed using ANOVA procedures by first checking homogeneity of variance. Generalised linear modelling procedures were employed to determine the relationship between BGC damage and topography, agro-ecological zones, age of trees and host species; BGC was found to be spreading fast and had infested the five provinces of Kenya. It was observed that there was significant difference on the mean severity between provinces and districts. Agro-ecological zones had significant difference on the mean severity. Further studies of the effect of factors that affected the distribution and severity patterns of BG Cshould be conducted.