Field test for the parasitoid Psyttalia concolor (Szépligeti) in Tuscan olive groves (Italy)

Abstract: Field-controlled releases of Psyttalia concolor were made in some Tuscan olivegroves, during 2007 and 2008. Seven days-old mated native P. concolor females were releasedinto field-cages containing branches of olive trees, each with 100 olive fruits, and maintained for24 hrs. After this period, the drupes were collected and transferred to the laboratory (20 ± 1°C, 50± 10 R. H.) to wait for the parasitoids emergence. Two parasitoid densities were tested, 10 and 20females/cage, and 5 replicates were made. Simultaneously, a large number of olive fruits (500)were randomly collected and dissected, to estimate the olive fruit fly infestation. Results showedthat P. concolor can successfully parasitize olive fruit fly larvae under field-controlled conditions.The mean parasitization rate ranged from a minimum of about 19% (in 2007, treatment 10females/cage) to a maximum of about 44% (in 2008, treatment 20 females/cages). During the 2ndyear of trial, the olive fruit fly preimaginal population consisted mostly of 1st and 2nd instar larvae,so confirming our previous laboratory observations on the ability of P. concolor to locate andsuccessfully parasitize young larval host instars.