Diversity in Eucalyptus susceptibility to the gall-forming wasp Leptocybe invasa

Abstract

1 Extensive variation to damage by the invasive gall-forming wasp Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) is known to exist amongst Eucalyptus genotypes. 2 In the present study, 30 of the 50 tested genotypes were susceptible to gall formation and development of the wasp. Gall development on the petiole and leaves of plants was compared to calculate the percentage of infestation per plant and per genotype. 3 A positive correlation between galls on petioles and leaves indicated an absence of specificity at this level, and also that either leaves or petioles could be used to obtain an accurate estimate of the level of infestation. 4 Genotypes of E. nitens × E. grandis and E. grandis × E. camaldulensis were most susceptible, with a maximum damage index value for leaves and petioles of 0.52 and 0.39, respectively. Eucalyptus dunii, E. nitens, E. smithii, E. urophylla and E. saligna × E. urophylla showed little or no infestation. 5 The results obtained in the present study suggest that the selection and planting of resistant/less susceptible genotypes will be an important aid in managing damage from L. invasa invasion.