Field performance and fitness of an olive fruit fly parasitoid, Psyttalia humilis ( Hymenoptera: Braconidae), mass reared on irradiated Medfly

Abstract

Adult Psyttalia humilis (Silvestri) were produced from irradiated larvae of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), at the USDA-APHIS-PPQ, Moscamed biological control laboratory, San Miguel Petapa, Guatemala, and shipped to the USDA-ARS, SJVASC, Parlier, from September 2008 to January 2009 for biological control of olive fruit fly, Bactrocera oleae (Rossi), in California. In total, 230,908 individuals were shipped to California and 202,328 were released in the field, a 12.4% mortality rate from shipment to release. Thirteen sample sites were located in nine counties; 11 sites received parasitoids from September 2008 to January 2009 (range: 3114–55,826 per site). Olive fruit fly population density, as measured by adult traps, varied greatly among sites and sample dates – ranging from <1 fly per day (sites in San Joaquin Valley and Sacramento Valley) to 29 individuals per day in (San Jose, CA). Adult emergence of olive fruit fly and P. humilis from >10,000 fruit collected, across all sites and sample dates, showed parasitism ranging from 0–17%. Laboratory studies were conducted to determine the fitness of P. humilis reared on irradiated and fertile C. capitata. Results showed no difference in parental size, progeny produced during a 48 h period, or the number female: male offspring produced; there were significantly fewer eggs in the dissected ovaries of irradiated than fertile female P. humilis. Continuous flight in different air temperatures and air speeds for female and male parasitoids showed no difference in female or male P. humilis reared on irradiated C. capitata or female P. humilis reared on fertile olive fruit fly. Results are discussed with respect to the establishment and effective use of P. humilis for control of olive fruit fly in California’s varying climatic regions where olives are grown.