|BAUER, LEAH - Us Forest Service (FS)|
|ABELL, KRIS - University Of Massachusetts|
|LELITO, JON - Animal And Plant Health Inspection Service (APHIS)|
|VAN DRIESCHE, ROY - University Of Massachusetts|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2013
Publication Date: 6/1/2013
Citation: Duan, J.J., Bauer, L., Abell, K., Lelito, J., Van Driesche, R. 2013. Establishment and abundance of Tetrastichus planipennisi (Hymenoptera: Eulophidae) in Michigan: potential for success in classical biocontrol of the invasive emerald ash borer (Coleoptera: Buprestidae). Journal of Economic Entomology. 106:1145-1154.
Interpretive Summary: The emerald ash borer (EAB) is a relatively new invasive forest pest in North America, which has killed hundreds of millions of native North American ash (Fraxinus spp.) trees since its discovery in Michigan, USA in 2002. Classical biological control through the introduction and establishment of co-evolved natural enemies from the native ranges of EAB (Northeast Asia) can be an extremely cost-effective, sustainable, and environmentally benign tool for management of this pest. The parasitic wasp Tetrastichus planipennisi is a natural enemy of EAB larvae in northeast China, and was recently introduced to the US for biological control of EAB in 2007. In the present study, we documented that three to four years after the field releases, this parasitic wasp is widely established in EAB-infested ash stands in both release and control plots of six study sites in southern Michigan. Four years after the parasitoid releases, the proportion of sampled trees observed with this natural enemy increased to 91% and 83% in the parasitoid-release and control plots, respectively. Similarly, parasitism rate of EAB larvae by this parasitic wasp also increased sharply from 1.2% in the first year after parasitoid releases to 21.2% in the parasitoid-release plot in the fourth year and from 0.2% to 12.8% for the control plots. These results demonstrate that this EAB-biocontrol agent is widely established in southern Michigan and that its populations are increasing and expanding. This suggests that this natural enemy is likely to play a critical role in suppressing EAB populations in central Michigan.
Technical Abstract: Tetrastichus planipennisi Yang is a gregarious larval endoparasitoid native to China, and has been introduced to the United States since 2007 for classical biological control of the invasive emerald ash borer (EAB), Agrilus planipennis Fairmaire, an exotic beetle responsible for widespread ash mortality. Between 2007 – 2010, T. planipennisi adults (3,311 – 4,597 females and ˜1500 males) were released into each of six forest sites in three counties (Ingham, Gratiot, and Shiawassee) of southern Michigan. Approximately four years after these field releases, T. planipennisi was found to be widely established on EAB-infested ash trees in both release and control plots across the study area. Four years after the parasitoid releases, the proportion of sampled trees with one or more broods of T. planipennisi increased to 91% and 83% in the parasitoid-release and control plots, respectively. Similarly, the mean number of T. planipennisi broods observed from sampled trees increased from less than one brood per tree in the first year (2009 fall for Ingham county sites and 2010 for other sites) after parasitoid releases to 2.46 – 3.08 broods in the 3rd or 4th year (fall 2012) after parasitoid releases. The rates of EAB larval parasitism by T. planipennisi also increased sharply from 1.2% in the first year after parasitoid releases to 21.2% in the parasitoid-release plots in the fourth year, and from 0.2% to 12.8% for the control plots. These results demonstrate that T. planipennisi is established in southern Michigan and that its populations are increasing and expanding. This suggests that T. planipennisi is likely to play a critical role in suppressing EAB populations in Michigan.