Thermal performance of two indigenous pupal parasitoids attacking the invasive Drosophila suzukii (Diptera: Drosophilidae)

Authors: WANG, XIN-GENG - University Of California; SERRATO, MICHAEL - University Of California; SON, YOUNGSOO - California Department Of Food And Agriculture; WALTON, VAUGHAN - Oregon State University; Hogg, Brian; DAANE, KENT - University Of California

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2018
Publication Date: 6/1/2018
Citation: Wang, X., Serrato, M.A., Son, Y., Walton, V.M., Hogg, B.N., Daane, K.M. 2018. Thermal performance of two indigenous pupal parasitoids attacking the invasive Drosophila suzukii (Diptera: Drosophilidae). Environmental Entomology. 47(3):764-772. https://doi.org/10.1093/ee/nvy053.
DOI: https://doi.org/10.1093/ee/nvy053

Interpretive Summary: Spotted wing drosophila is a pest of soft-skinned fruit such as strawberries, blueberries and cherries. Its ability to attack ripe fruit makes it a particularly damaging pest. Two species of parasitic wasp are among the few indigenous natural enemies that attack spotted wing drosophila in North America, and rearing and releasing these parasitoids in large numbers may help control this damaging pest. To this end, we examined the temperature requirements of both parasitoid species, and determined the optimal temperature for stockpiling the parasitoids before release. The parasitic wasp that occurs in both California and Oregon tolerated all temperatures from 12.6–32.8°C, whereas the other parasitic wasp failed to develop at or above 30°C, and was less tolerant of both low and high temperatures than the other parasitic wasp. Thus, one of the parasitic wasp species may be better adapted to regions with more variation in temperature, whereas the other species may be better suited to mild climates. To develop storage strategies for mass-rearing the parasitic wasps, we compared the cold tolerance of wasp larvae (in parasitized spotted wing drosophila) at 12°C for either 1, 2 or 3 months. Fewer wasps developed to adulthood as the duration of cold storage increased, and survival was higher for older larvae than for younger larvae. These results suggest that the wasp larvae can be stored at cold temperature for up to three months, but that one month is ideal.

Technical Abstract: Pachycrepoideus vindemiae (Rondani) and Trichopria drosophilae (Perkins) are among a few indigenous parasitoids attacking the invasive Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) in North America. Both parasitoid species occur in California, whereas only P. vindemiae has been reported from Oregon. We compared the thermal performance of the California populations of P. vindemiae and T. drosophilae, and the Oregon population of P. vindemiae at eight constant temperatures (12.6–32.8'C). Both P. vindemiae populations could develop at all tested temperatures. Trichopria drosophilae failed to develop at or above 29.6'C. This species was, however, able to develop at a diurnal temperature regime of 15–32'C, and survival was higher in older developmental stages. Trichopria drosophilae was less tolerant to both low and high temperatures than P. vindemiae whereas the Oregon P. vindemiae population was more cold-tolerant but less heat-tolerant than the California population in terms of offspring survival, development and reproduction. To develop storage strategies for mass-cultured parasitoids, we compared the cold tolerance of immature P. vindemiae and T. drosophilae of the California populations at 12°C for 1, 2 or 3 months, followed by a 23ºC holding period. Successful development to the adult stage decreased as cold storage duration increased. Successful development however increased when cold storage was initiated during the older developmental stages for 1-month exposure for both parasitoid species. The results are discussed with regards to parasitoid thermal adaptation and the potential use of P. vindemiae and T. drosophilae for biological control of spotted-wing drosophila.