Biological control of olive fruit fly through inoculative releases of Opius concolor Szépl

A field trial of biological control of Bactrocera oleae (Gmel.) by means of inoculative
releases of Opius concolor Szépl. was performed during 1997 – 2001 in an olive grove of 30 ha in
northwestern Sardinia (Italy). The total number of parasitoids released per year, based on the density
of infestation of the olives and the level of parasitism determined by O. concolor, varied between 36
and 225 adults per plant.
The maximum parasitism rate in the years 1997, 1998, 2000 and 2001 reached, respectively, 82,
62, 77 and 100% and was null in 1999. The high variability observed in the parasitism rate can be
attributed to several factors: poor quality of mass-reared parasitoids, extremely high abundance of
olive fly population during years of low yield, and the higher growth rate of B. oleae population
compared to that of O. concolor. The results showed that inoculative releases of O. concolor were
sufficient to control B. oleae infestation in years of high yield.