PI(s): Kok, Loke T (Co-Project Leader), Salom, Scott M (Co-Project Leader)

Investigators: Beck, Mary (Jess) (Investigator), Mays, Ryan (Investigator), Eisenback, Brian M (Investigator), McAvoy, Tom J. (Investigator), Dellinger, Theresa (Tree) (Investigator), Mausel, David Logan (Investigator), Lamb, Ashley (Investigator), Jubb, Carrie S (Investigator), Davis, Gina (Investigator), Gatton, Holly (Investigator)

Abstract: We are part of a large scale effort to manage the hemlock woolly adelgid in the eastern U.S. Our work encompasses the complete spectrum of biological control activities including foreign exploration, quarantine evaluation, mass production, release, and evaluation of approved insect natural enemies. You can read more about our work at http://www.research.vt.edu/resmag/2007summer/bugs.html

Description:

 The following projects are ongoing:

1. Foreign exploration for additional insect natural enemies of HWA in China and Japan

We are participating in a large-scale coordinated effort to find and study HWA and its predators in China and Japan. The goals are to identify new potential biological control agents for possible introduction into the eastern U.S. and to improve the consistency in shipping already identified predators. In the past 4 years, 3 new species of Laricobius (Coleoptera: Derodontidae) have been discovered. These are adelgid-specific predators and have good potential as biological control agents for the hemlock woolly adelgid.

2. Quarantine evaluation of Derodontid and Anthocorid predators collected from Asia

Targeted predators species identified and collected in the foreign exploration project will be sent to the Quarantine lab at Virginia Tech, one of two targeted facilities in the U.S. to process and study incoming natural enemies for HWA. The biology and host-range evaluations of the imported predators are being studied for considerationas biological control agents.

3. Mass production, release, and evaluation of a specialist predator, Laricobius nigrinus (Col.: Derodontidae)

Mass rearing procedures were developed at Virginia Tech and in addition to our insectary, Clemson and Univ. of Tennessee began rearing this beetle in 2005 in an attempt to maximize production for operational release. By the end of 2005, over 22 research-based and more than 8 operational releases of beetles have taken place throughout the eastern U.S. Pre- and post-release data are being collected at each site to evaluate and study the establishment and impact of this biological control agent on HWA

4. Competitive interactions among two newly introduced specialist and one established generalist predator of HWA

Since multiple species of predators are being released, this project focuses on competition among L. nigrinus, another adelgid-specialist, Sasajiscymnus tsugae, and an already established exotic generalist predator, Harmonia axyridis. Lab and field studies have shown that interspecific interaction are minimal in regards to survival, feeding on prey, and egg production. Most competition appears to occur within species.

5. Indirect effects of sublethal dosages of imidacloprid on survival and performance of two specialist predators of HWA

Biological control agents are being released throughout the range of eastern hemlock where trees are infested but are still relatively healthy. In many of these areas, targeted trees are also being treated with systemic insecticides. We are attempting to see if both pest management tactics are compatible in the same locations. Our preliminary data suggest that the predators are susceptible to pesticide poisoning by feeding on prey poisoned by insecticides. Ongoing studies will determine the extent to which this can be expected to take place.

Impact:

Hemlock woolly adelgid has now spread to cover 50% of the geographic range of eastern hemlock. In the past 20 years, this invasive pest has left most of the trees it has enountered either dead or in a highly weakened state. Since 1997, the major emphasis for addressing the problem has been investment into biological control. Operational releases of three different pre-specific predator species in now ongoing. Efforts to find additional predators as well as determine how best to establish the predators currently being released is critical for optimizing the biological control effort. The jury is still out whether this will work, but the effort must be made if there is to be a chance to save the hemlock resource.