2010 Annual Report
1a.Objectives (from AD-416)
The purpose of this agreement is to quantify the impact of introduced parasitoids on the survival of emerald ash borer (EAB), Agrilus planipennis Fairmaire, populations. The work will be done in the US, using one species of American ash (Fraxinus pennsylvanica). Evaluations will be based on life tables developed from marked cohorts of eggs and larvae at six field sites in natural forests where the parasitoids imported to the US to control EAB either have already been released or will be released in the first year of the study. Specific objectives will be:
1. Locate 3 control and 3 treatment sites. At the treatment sites, release the three EAB parasitoids imported from China (Oobius agrili, Tetrastichus planipennisi , Spathius agrili).
2. At all sites, assess the impact of parasitoids on cohorts of EAB eggs and larvae/pupae in green ash (F. pennsylvanica)
3. Use data from EAB cohort studies to develop life tables for EAB populations and compare stage specific survival rates and other life table parameters.
1b.Approach (from AD-416)
We will test whether parasitoids introduced from China will greatly reduce survival of emerald ash borer cohorts on green ash trees (F. pennsylvanica) in U.S. Work will be done in Michigan at three control and three treatment sites, the latter where three introduced EAB parasitoids either have been or will be released. Cohorts of EAB eggs and larvae/pupae will be created at each site, and used for construction of site-specific life tables for measuring the impact of released parasitoids.
Following the previous years field releases of three introduced parasitoids (T. planipennisi, S. agrili, and O. agrili) in 2008 and 2009, five to six ash trees infested with emerald ash borers at each of the three study sites in Michigan were sampled in the spring and summer of 2010 to assess the establishment of the released parasitoids. Results indicated that the larval endoparasitoid T. planipennisi and egg parasitoid O. agrili were consistently recovered from all three study sites in Michigan, and resulted about 10–30% parasitism of EAB larvae and <5% of EAB eggs, respectively. In contrast, the larval ectoparasitoid Spathius agrili was recovered less frequently (only in one study site in Michigan), and resulted <0.5% parasitism. In comparison to parasitism by the introduced parasitoids, host tree defense and woodpecker predation inflicted 5– 41% of the emerald ash borer larvae observed in different study sites.
In addition, more cohorts of EAB eggs and larvae have established in the summer of 2010, will be sampled in the spring of 2011 or fall of 2011 to further measure the impact of the introduced EAB parasitoids as well as other mortality factors (such as native parasitoids, host plant defense, and woodpecker).