The Abundance and Population Dynamics of Leptocybe invasa (Hymenoptera: Eulophidae) Galls on Eucalyptus spp. in China

The blue gum chalcid, Leptocybe invasa Fisher & La Salle, invaded China in 2007 and has subsequently caused substantial damage to eucalyptus trees. In the current paper, we investigated the susceptibility of 10 Eucalyptus spp. and Eucahetus dunnii to L. invasa in the field, determined the density of galls as well as the gall volume on these tree species, and monitored the population dynamics of wasps in Hainan and Guangdong provinces of China. The order of susceptibility to L. invasa was Eucalyptus urophylla×Eucalyptus camaldulensis>E. urophylla (coppices)>Eucalyptus exserta> Eucalyptus grandis×E. urophylla in Hainan, and Eucalyptus propinqua>Eucalyptus saligna>E. exserta>Eucalyptus microcorys>Eucahetus dunnii>E. camaldulensis>Eucalyptus tereticornis>Eucalyptus robust in Guangdong, China. Although L. invasa generally damages the midribs and petioles of young leaves and the tender bark of twigs of eucalyptus, galls were not observed on leaves of E. microcorys, E. camaldulensis, or E. dunnii. Gall volume significantly differed among the tree species, and gall volume and wasp number were positively correlated. In Dongfang, Hainan Province, the overwintering period of L. invasa emergencing through the year was from the end of December to March of the next year, and the number of population was the greatest on E. urophylla×E. camaldulensis, and the smallest on E. grandis×E. urophylla. In Guangzhou, Guangdong Province, L. invasa hardly emerged in winter from December to June of the next year, and the population was the greatest on E. propinqua, and the smallest on E. microcorys.