|Larson, Kristi - University Of Massachusetts|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2016
Publication Date: 8/3/2016
Citation: Larson, K.M., Duan, J.J. 2016. Differences in the reproductive biology and diapause of two congeneric species of egg parasitoids (Hymenoptera:Encyrtidae) from northeast Asia: implications for biological control of the invasive emerald ash borer. Biological Control. 103:30-45.
Interpretive Summary: Knowledge about the biology and life history of insect natural enemies is important to the development of biological control programs against agricultural or forest pest such as the invasive emerald ash borer (EAB) that has killed tens of millions of North American ash trees since it was detected here in 2002. Two parasitic wasps (Oobius primorskyensis and Oobius agrili) are closely related-species of natural enemies attacking emerald ash borer eggs in their native range of northeast Asia. While one (O. primorskyensis) is currently being evaluated in quarantine for potential biocontrol introduction against EAB in the U.S., the other (O. agrili) has established self-sustaining populations in some areas of the U.S. since its first introduction in 2007. Scientists from USDA ARS in collaboration with the University of Massachusetts compared the reproductive biology and offspring dormancy of these two natural enemies. Results of the study show that there are distinctive differences in the reproductive biology and offspring dormancy pattern between the two natural enemy species. These findings suggest that the effectiveness of these natural enemies for classical biocontrol of EAB may vary in different regions of U.S, where the EAB emergence and oviposition time differ. Considering the differences in their reproductive biology and dormancy pattern, these two species of EAB natural enemies may also be complementary to each other in reducing EAB egg densities in regions where both species can be successfully established.
Technical Abstract: Oobius primorskyensis Yao and Duan and Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) constitute a cryptic species complex of egg parasitoids attacking the emerald ash borer Agrilus planipennis (Coleotpera: Buprestidae) in their native range of northeast Asia. While O. primorskyensis is currently being evaluated in quarantine for potential biocontrol introduction against A. planipennis to the U.S., O. agrili has established stable populations in some areas of the U.S. since its first introduction in 2007. In the present study, we quantify and compare the survivorship, fecundity and progeny diapause between O. primorskyensis and O. agrili for both diapaused and non-diapaused populations. Both parasitoid species were reared with fresh A. planipennis eggs at 25 ± 1°C, ˜65% RH, and 16: 8 h L: D photoperiod in the study. Results of the study demonstrate that there are distinctive differences in the reproductive biology and progeny diapause pattern between the two parasitoid species as well as between diapaused and non-diapaused populations within each species. Adults of diapaused O. primorskyensis populations have significantly longer longevity and produce significantly more progeny over their lifetime than those of diapaused O. agrili. Although there is no significant difference in their longevity, adults of the non-diapaused O. priomorskyensis population produced significantly less progeny than those of non-diapaused O. agrili. While a majority (>64%) of the progeny produced by diapaused O. primorskyensis as well as by both diapaused and non-diapaused O. agrili continued development to adults, nearly 100% of the progeny from non-diapaused O. primorskyensis population entered diapause. These findings suggest that the effectiveness of O. priomorskyensis and O. agrili in classical biocontrol of A. planipennis may vary in different regions of North America, where the host phenology in adult emergence and oviposition peak differ. Considering the differences in their reproductive biology and diapause pattern for risk-spreading, O. priomorskyensis and O. agrili may also be complementary to each other in reducing host egg densities in regions where both species can be successfully established.