Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2012
Publication Date: 6/1/2012
Citation: Yokoyama, V.Y., Wang, X., Aldana, A., Caceres, C.E., Rendon, P.A., Johnson, M.W., Daane, K.M. 2012. Performance of Psyttalia humilis (Hymenoptera: Braconidae) reared from irradiated host on olive fruit fly (Diptera: Tephritidae) in California. Environmental Entomology. 41:497-507. Interpretive Summary: Olive fruit fly is a destructive pest of olives in California and jeopardizes the production of canned olives and olives grown for oil in the only state that produces these commodities for the nation. A parasitoid that is mass reared on Medfly at the USDA-APHIS-PPQ Moscamed facility in Guatemala was imported and used for biological control of olive fruit fly. During the rearing process, irradiation of the Medfly host was used a technique to ensure that the fruit fly pest would not contaminate parasitoid shipments to California. The parasitoids produced by this method were found to be fit, vigorous, and readily attacked olive fruit fly upon release in California olive orchards. The use of sterilized host increases the safety of importing biological control agents for major crop pests and helps reduce costs for rearing these beneficial insects. The work supports the exclusive California canned olive crop and emerging olive oil industries.
Technical Abstract: The parasitoid Psytallia humilis (Silvestri) was reared on Mediterranean fruit fly, Ceratitis capitata (Wiedemann), larvae irradiated at different doses from 0-70 Gy at the USDA, APHIS, PPQ, Moscamed biological control laboratory in San Miguel Petapa, Guatemala and shipped to the USDA, ARS, Parlier, CA. Percentage females and non-emerged adults, number of progeny per female and percentage parasitism ranged from 53-62%, 12-34%, 1.4-1.8, and 19-24%, respectively, for parasitoids reared from irradiated host. Host irradiation dose had no significant effect on P. humilis adult body size based on forewing length, parasitism of olive fruit fly, Bactrocera oleae (Rossi), or percentage female progeny. Dissected 1-wk old female parasitoids reared from hosts irradiated with 70 Gy had a significantly lower number of mature eggs than females from non-irradiated hosts, but no significant differences were found among females from hosts irradiated with 0-60 Gy. Longevity of P. humilis adults decreased with increased temperature from 15-35ºC, regardless of food provisions, gender, and host irradiation dose. Female parasitoids survived 6-7, 2 and 1-2 d without food; 8-9, 3, and 2 d with water; and 37-49, 20-24, 5-7 d with water and food; and males survived 2-4, 1, and 1 d without food; 4, 1, and 1 d with water; and 8-16, 3-5, and 2-3 d with water and food at 15, 26 and 35ºC, respectively. Adult P. humilis reared from fertile Medfly and aspirated from emergence cages for dispensing in cups lived significantly longer than those chilled and dispensed by weight after shipment, provided with water and honey and held at a room temperature of 23ºC and 35% RH. No parasitoids departed release cages at 12°C and at 21 and 32°C, 50% of the adults departed after 180 and 30 min, respectively. Rates of departure were proportional to time and temperature and significant differences were found in departure rates among the temperatures at 30, 60 and 90 min. Thirteen shipments of P. humilis (2,980 to 21,922 parasitoids per shipment) were received between September and December 2009, and seven shipments (7,502 to 22,560 parasitoids per shipment) were received between October and December 2010 from San Miguel Petapa, Guatemala. Daily number of olive fruit fly adult and percentage female trap captures ranged from < 1-19 and 8-58% in 2009 and < 1-11 and 0-42% in 2010, respectively. Daily mean temperatures and RH ranged from 6-21°C and 37-82% in 2009 and 8-18°C in 2010. The number of parasitoids released ranged from 848-12,257 in 2009 and 3,675-11,154 in 2010. Calculated percentage parasitism of olive fruit fly third instars at all locations ranged from 0-9% in 2009 and 0-36% in 2010.