Effect of exposure time on mass-rearing production of the olive fruit fly parasitoid, Psyttalia lounsburyi (Hymenoptera: Braconidae)

Authors: LA-SPINA, MICHELANGELO - Vineland Research And Innovation Centre; PICKETT, CHARLES - California Department Of Food And Agriculture; DAANE, KENT - Environmental Science Extension Center; Hoelmer, Kim; BLANCHET, ARNAUD - US Department Of State; Williams, Livy

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2017
Publication Date: 12/11/2017
Citation: La-Spina, M., Pickett, C.H., Daane, K.M., Hoelmer, K.A., Blanchet, A., Williams III, L.H. 2017. Effect of exposure time on mass-rearing production of the olive fruit fly parasitoid, Psyttalia lounsburyi (Hymenoptera: Braconidae). Journal of Applied Entomology. 142(3):319-326. https://doi.org/10.1111/jen.12478.
DOI: https://doi.org/10.1111/jen.12478

Interpretive Summary: Biological pest control programs often rely on mass-production of high quality beneficial insects for subsequent releases into the field. U.S. olive production is centered in California, where an exotic, invasive insect pest has severely impacted olive production for more than 15 years. A beneficial insect that kills the pest is being reared under laboratory conditions to support a biological pest control program in California. The mass-rearing system for this beneficial insect was evaluated with the goal of increasing production while at the same time reducing the time requirements for rearing. We tested the effect of duration of time that the pest insect was exposed to the beneficial insect on several aspects of the reproductive biology of the beneficial insect. Parasitization rates were highest at 3- and 4-hour exposure times, while production (i.e., emergence of beneficial insect progeny) was highest at the 2-hour exposure time. Multiple attacks on a single pest host occurred at very low levels and did not appear to be a factor affecting beneficial insect production. The sex ratio of beneficial insect progeny was male-biased and did not vary significantly over different exposure times. The rate of stings by the beneficial insect on pest hosts increased with exposure time and was consistent with decreases in pest development from immature to adult. Our findings indicate that when compared to current rearing procedures, the 2-hour exposure time resulted in an overall 2.8-fold increase in beneficial insect production when standardized for time. These results will help optimize mass-rearing of the beneficial insect, and lead to improved pest control in California olives.

Technical Abstract: Classical biological control programs rely on mass-production of high quality beneficial insects for subsequent releases into the field. Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) is a koinobiont larval-pupal endoparasitoid of tephritid flies that is being reared to support a classical biological control program for olive fruit fly in California. The mass-rearing system for a P. lounsburyi colony, initiated with insects originating in Kenya, was evaluated with the goal of increasing production while at the same time reducing the time requirements for rearing in a quarantine facility. We tested the effect of exposure time of a factitious host larvae, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), on parasitization, superparasitism, production, and sex ratio of P. lounsburyi, and survival of the host. Parasitization rates were highest (ca. 31%) at 3- and 4-hour exposure times, while production (i.e., emergence of wasp progeny) was highest (ca. 16%) at the 2-hour exposure time. Superparasitism occurred at low levels (ca. 1.47%) and did not appear to be a factor affecting parasitoid production. The sex ratio of wasp progeny was male-biased and did not vary significantly over different exposure times. The rate of stings on host larvae increased with exposure time and was consistent with decreases in pupal egression from larvae and emergence rate of adult flies. When compared to current rearing procedures, the 2-hour exposure time resulted in an overall 2.8-fold increase in P. lounsburyi production when standardized for time.