Variation in leptocybe invasa (Hymenoptera: Eulophidae) population intensity and infestation on eucalyptus germplasms in Uganda and Kenya.

Abstract

Leptocybe invasa, an invasive gall-inducing wasp of Australian origin, recently emerged as a serious eucalyptus pest of global importance. We examined the spatial and temporal variations in L. invasa adult populations and evaluated eucalyptus gemplasms for infestations by the wasp in Uganda and Kenya. There were significant differences in L. invasa abundance, gall incidence, severity and damage index between sites. Adults occurred throughout the year, indicating overlapping generations since the adults are known to live <7 d. There was no obvious peak in L. invasa population abundance although a general decline was observed in dry months. Out of 35 eucalyptus germplasms evaluated for L. invasa infestations, only Eucalyptus henryi and the clonal hybrids GC 578 and GC58 I were resistant to the pest. Most germplasms were ranked as tolerant or moderately susceptible to wasp attack. Highly susceptible germplasms included Eucalyptus camaldulensis, GC540 and GC784 in Tororo, Uganda, and MAUl, GCI4, GCI5 and GCIO in Busia, Kenya. Implications of the year-round occurence of L. invasa adult populations and gall infestations, and the potential for host resistance in managing the pest, are discussed.