Variability in the Infestation of Leptocybe Invasa (Hymenoptera: Eulophidae) on Commercially Grown Eucalyptus Germplasm in Kenya

Abstract

The growing of Eucalyptus trees in Kenya is widespread and there is high demand for their products. Infestation of Eucalyptus germplasm by Leptocybe invasa Fisher & LaSalle, a new pest, is causing a lot of worry since very little is known about the pest. Variability in the infestation of L. invasa on commercially grown Eucalyptus germplasm was examined in two trial sites established in western Kenya. The crown foliage gall density and gall count on a sample unit were used to determine the levels of infestation. Using analysis of covariance procedure and separation of means using least significant difference, the tested germplasm was classified into four susceptibility groups. The incidence and severity of L. invasa increased with age and were generally high in Eucalyptus hybrid clones as compared to improved Eucalyptus hybrids and species. However, Eucalyptus henrii and GC581 were found to be resistant to L. invasa. There was a significant positive correlation (corr. = 0.712) between the mean L. invasa gall count and the mean crown damage thus reinforcing use of the latter as a cost-effective method of assessing infestation of L. invasa. The use of resistant germplasm to L. invasa requires promotion for adoption as a management strategy. However, further research needs to be carried out on identifying the genes responsible for this resistance.