Evaluation of an indigenous parasitoid Habrobracon gelechiae (Hymenoptera: Braconidae) for biological control of light brown apple moth Epiphyas postvittana (Lepidoptera: Tortricidae) in California

Abstract

Light brown apple moth, Epiphyas postvittana (Walker), is a newly invasive pest in California. Habrobracon gelechiae Ashmead is an indigenous North American ectoparasitoid of lepidopterans. Using E. postvittana as the host, we determined H. gelechiae host stage preference for oviposition and suitability for larval growth: the parasitoid attacked second to fifth instars, but preferred older (third to fifth) host larvae for oviposition, laying more eggs per clutch on the largest (fifth instar). Offspring survival was better on larger (third to fifth instars) hosts. Adult survival and fecundity and immature temperature development were studied at three key temperatures. At 12°C, H. gelechiae failed to oviposit. At 22 and 30°C, H. gelechiae had, respectively, egg to adult developmental times of 15.4 and 8.7 days, adult female survival of 54.8 and 27.2 days, lifetime parasitism of 39.9 and 21.8 hosts and 181 and 151 eggs per female, an intrinsic rate of increase of 0.107 and 0.165, and mean generation time 30.7 and 18.9 days. We studied intraguild interactions with the endoparasitoid Meteorus ictericus Nees, and found that H. gelechiae did not discriminate against hosts that were parasitised by M. ictericus. Neither the paralysing venom injected by H. gelechiae or the presence of the ectoparasitoid's eggs or larvae arrested M. ictericus development. We also conducted a field release of H. gelechiae on two plant species commonly infested by E. postvittana and showed that H. gelechiae was able to locate and attack moth larvae on both hosts.

Keywords:

• biological control
• host stage preference
• interspecific competition
• light brown apple moth

Acknowledgements

The authors thank Jeno Papp (Hungarian Natural History Museum, Budapest, Hungary) for the identification of H. gelechiae and John Luhman (University of Minnesota) and John Heraty (University of California, Riverside) for the identification of some other parasitoids mentioned in this study. They also thank William Roltsch (California Department of Food and Agriculture) for facilitating field studies; Addie Abrams and Elizabeth Pierson (University of California, Berkeley) for laboratory and field assistance; Nicholas Mills and Linda Bürgi (UC Berkeley) for helpful discussions during this study; and Alan Sawyer (USDA-APHIS-PPQ-CPHST) for facilitation of the research. Funding was provided by USDA-APHIS08-8100-1310 and the California Specialty Crop Block Grants.