|Bauer, Leah - Us Forest Service (FS)|
|Abell, Kristopher - University Of Massachusetts|
|Ulyshen, Michael - Us Forest Service (FS)|
|Van Driesch, Roy - University Of Massachusetts|
Submitted to: Journal of Applied Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2015
Publication Date: 7/23/2015
Citation: Duan, J.J., Bauer, L., Abell, K.J., Ulyshen, M.D., Van Driesch, R. 2015. Population dynamics of an invasive forest insect and associated natural enemies in the aftermath of invasion: implications for biological control. Journal of Applied Ecology. DOI: 10.1111/1365-2664.12485.
Interpretive Summary: Emerald ash borer (EAB) is an invasive pest that has killed millions of ash trees in the United States and Canada. Scientists from ARS BIIRU, US Forest Service, and University of Massachusetts studied small stingless wasps introduced from Asia (biological control agents) for EAB control over a seven year period (2008 – 2014) in southern Michigan. Results showed that the number of EAB larvae in ash trees declined by about 80% from 2009 to 2014. The decline of EAB larvae in the study sites was attributed to increases in EAB mortalities caused by native wasps and other predators as well as by the introduced biocontrol agents. Findings of our study point to the potential for success in our current biological control program against EAB.
Technical Abstract: Understanding the population dynamics of exotic pests and associated natural enemies is important in developing sound management strategies in invaded forest ecosystems. The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive phloem-feeding beetle that has killed tens of millions of ash (Fraxinus) trees in North America since first detected in 2002. We surveyed populations of immature EAB stages and associated natural enemies over a seven year period (2008 – 2014) in six stands of eastern deciduous forest in southern Michigan, where Tetrastichus planipennisi Yang and other Asian-origin parasitoids were released for biological control between 2007 and 2010. Densities of live EAB larvae in infested ash trees at both parasitoid-release and control forest plots peaked at ca. 40 – 46 live larvae per m2 of ash phloem area in 2009 and declined thereafter by ˜ 80% (6 – 8 larvae per m2 of ash phloem) by the fall of 2014.No differences in EAB density or mortality rates (by parasitoids, avian predators or other biotic factors) were observed between parasitoid release and control plots. These findings reflect the unexpectedly rapid dispersal rates exhibited by the introduced parasitoid, T. planipennisi. The decline of EAB larval density in the six study sites was correlated with significant increases in EAB larval parasitism, first by the native parasitoids and then by T. planipennisi. Life table analyses further indicated that parasitism by both the introduced control agent and the North American native parasitoids contributed significantly to the reduction of net EAB population growth rates in our study sites from 2010 to 2014. These findings point to the potential for success in biological control of the invasive forest pest, particularly in the aftermath of invasion.