2011 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.
While cohorts of EAB eggs and larvae we established in the summer of 2010 at three different study sites will be sampled in the fall of 2011, life table analysis of impact of parasitoids on EAB populations in Michigan have been conducted using data collected in 2009 and 2010 on two generations of EAB populations. Results from the life table analysis of EAB population dynamics of the two previous generations showed the exploding EAB population (with population growth rate R0=17.5) in Michigan was reduced to an expanding population (R0=3.5) from 2009 to 2010 by three major native biotic factors including parasitoids, woodpeckers, disease, competition, and host plant resistance. The life table analysis further indicated that additional 30 – 40% larval parasitism or 70 -80% egg parasitism would result in a stable or shrink EAB population (R0<1). Results from the life table analysis demonstrate that parasitoids introduced from EAB’s native home (Asia) have the potential to shrink EAB population in North America.