Comparison of thermal performances of two Asian larval parasitoids of Drosopihila suzukii

Authors: Hougardy, Evelyne; Hogg, Brian; Wang, Xingeng; DAANE, KENT - University Of California

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2019
Publication Date: 5/30/2019
Citation: Hougardy, E.H., Hogg, B.N., Wang, X., Daane, K. 2019. Comparison of thermal performances of two Asian larval parasitoids of Drosopihila suzukii. Biological Control. 136. https://doi.org/10.1016/j.biocontrol.2019.104000.
DOI: https://doi.org/10.1016/j.biocontrol.2019.104000

Interpretive Summary: In biological control, natural enemies are introduced to help control invasive pests. The natural enemies are typically from the native range of the invasive pest, and must be tested before they are released to ensure that they will not attack native species, and that they will establish and help control the pest. One factor that can dramatically influence the establishment of biological control agents is climate. We tested the temperature requirements of two species of parasitic wasp that may help control spotted wing drosophila, a fruit fly from Asia that has invaded the US, where it has become a major pest of soft-skinned fruits such as cherries, blueberries and raspberries. The wasps attack the larvae of spotted wing drosophila, which feed on the fruit and cause it to rot. The two wasp species were collected from both China and South Korea, and populations from both countries were included in tests. Development, survival and reproduction of the wasps were tested at five different temperatures ranging from 12 to 30 C. The amount of time the wasps required to develop decreased as temperatures rose from 17 - 28 C; at higher temperatures, all wasps died and were unable to develop. Most wasps entered a state of dormancy when temperatures decreased below about 17 C. Adult female wasps of both species from South Korea produced more offspring than their Chinese counterparts at 16 C, suggesting that the wasps from South Korea are more efficient at low temperatures. These results suggest that the parasitic wasps should be able to survive in areas of the United States as far north as Michigan.

Technical Abstract: Ganaspis brasiliensis Ihering and Leptopilina japonica Novkovic & Kimura (Hymenoptera: Figitidae) are candidates for biological control of the spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilae), an invasive pest originally from East Asia. Developmental rate, offspring survival and reproductive success of a Chinese and a South Korean population of both species were assessed at different constant temperatures. Development time decreased with increasing temperature from 17 - 28 C; at 29.3 C no parasitoids completed their development. Temperatures below 17.2 C triggered a facultative diapause in both species and populations, and this cold temperature response varied among populations of different origin: South Korean populations of G. brasiliensis and L. japonica entered diapause at 17.2 C, whereas only a proportion of their Chinese counterparts entered diapause at the same temperature. No significant difference in offspring survival and offspring production were detected between populations in the mid-temperature range. However, offspring production at 15.9 C was higher for South Korean populations of G. brasiliensis and L. japonica compared with their Chinese counterparts, suggesting that the host location and oviposition behavior of the searching females was less affected by the cold temperature and/or their eggs had better cold hardiness. These variations in response to cold temperatures need to be further investigated and their ecological significance assessed to better understand performance of G. brasiliensis and L. japonica in the invaded regions where control is needed.