Control of the olive fruit fly,Bactrocera oleae, (Diptera: Tephritidae) through mass trapping and mass releases of the parasitoidPsyttalia concolor(Hymenoptera: Braconidae) reared on irradiated Mediterranean fruit fly

Abstract

Field studies were performed from 2002 to 2004 on Gökçeada Island, Turkey, to determine the effectiveness of releases of the larval–pupal parasitoid Psyttalia concolor Szepligeti against the olive fruit fly, Bactrocera oleae (Gmelin), alone and in combination with mass trapping, using EcoTraps®. For this, the parasitoid was reared on a factitious host, irradiated larvae of Ceratitis capitata (Wiedemann). Preparatory to making open-field augmentative releases, initial parasitoid releases were conducted throughout the 2001 season using confinement cages over branches bearing naturally infested olives into which parasitoids were introduced, using 1 ♀:♂ pair per 3 fruit oviposition punctures. Percent reduction in fly emergence due to parasitization in these cages was 26.9, 27.6, 18.0, and 24.7% from the first to the fourth olive fruit fly generations during the season, respectively. In 2002, open-field experiments were conducted in an experimental area (EA-1) containing 2500 olive trees. In this area, augmentative parasitoid releases and mass-trapping (MT) were combined, using 2000 EcoTraps. Following the first fruit oviposition punctures, parasitoids were released throughout the season, using ca. 26–40 parasitoids per tree per occasion. Damage of olives was reduced from an average of 87.6% in the control areas to only 18.1% in areas receiving mass trapping plus parasitoids. In 2003, the experiments were conducted in two areas. In EA-1 (=EA-1 in 2002), only parasitoid releases were made throughout the season, using ca. 27–34 parasitoids per tree per occasion. In EA-2, which contained 2000 olive trees, parasitoid releases were combined with 2000 EcoTraps and the parasitoids were released using ca. 20–30 parasitoids per tree per occasion throughout the season after occurrence of the first fruit oviposition punctures. Overall fruit damage rates of 10.6 and 10.1% were recorded in EA-1 (parasitoids only) and EA-2 (parasitoids + MT), respectively. Damage in the control area was 35.5%. In 2004, only parasitoid releases were conducted in EA-1. However, that year releases were begun early (in May) to attack the spring olive fly generation. Early season releases were made at ca. seven parasitoids per tree and late releases involved ca. 35 parasitoids per tree. Overall damage throughout the season was 12.2% in EA-1 vs. 37.9% in the control area. Our studies suggest that parasitoid releases are not enhanced by use of EcoTraps at the times and rates they were deployed. Despite the positive effects of both mass trapping and parasitoid releases, the reduction of damage by these means alone was not adequate to meet the requisite economic threshold of one to six larvae per fruit for table- and oil-varieties, respectively.