Dispersal rate and parasitism by Closterocerus chamaeleon (Girault) after its release in Sicily to control Ophelimus maskelli (Ashmead) (Hymenoptera, Eulophidae)

Abstract

Spread of the exotic parasitoid Closterocerus chamaeleon (Girault) and its parasitism on the Eucalyptus gall wasp Ophelimus maskelli (Ashmead) (Hymenoptera, Eulophidae) were studied in Sicily after C. chamae- leon introduction in May 2006. Parasitoid spread was evaluated by sampling sites at increasing distances from the five release sites. C. chamaeleon quickly established and spread; within 5 months, it caused 62% parasitism at release sites and 38% parasitism at sites 2 km from release sites. One year after its introduc- tion (spring 2007), C. chamaeleon was detected more than 50 km distant from release sites. By winter 2007–08, the parasitoid was recovered throughout Sicily and in many surrounding islets, with parasitism rates always >65% and usually at 100%. The dispersal rate was 0.15 km/month in the 2 months after release. It increased to 0.6 km/month in the next 3 months, reaching 7.5 km/month 5–7 months after release and 20 km/month in the following 11 months, when the entire island was colonized. The pattern of spread followed the spread latency model of biological invasions; the spread latency period was very short because of the parasitoid’s biological characteristics and a favourable environment. Parasitism trends differed between suburban and afforested sites, showing a longer spread latency period in the afforested sites due to the greater extent of potentially colonisable area. The parasitoid’s use of continu- ous and long-distance dispersal mechanisms enabled it to rapidly colonize even very distant regions and enhances its effectiveness as a biological control agent.