KSEF RDE: An innovative approach for elucidating trophic relationships of an invasive forest pest

We are requesting monies to develop an innovative approach for rapid, diagnostic determination of complex predator-prey interactions associated with an exotic, invasive species. We propose to use immunological techniques to understand the role of natural enemies in regulating populations of the hemlock woolly adelgid (HWA). HWA is an exotic invasive insect that is rapidly establishing itself in the eastern US, and was first reported in Kentucky in 2006. The adelgid is expanding its distribution in Kentucky and throughout the southern Appalachians, and is among the greatest biotic threats to eastern hemlock. An understanding of the emerging trophic relationships associated with newly establishing invasive species will help provide tools for development of viable management options, potentially minimizing their impacts. To fully comprehend interaction pathways within complex terrestrial food webs, it is necessary to characterize encounter frequencies of each constituent part of the web, and describe the consequence of these interactions. Determination of encounter frequencies is, in general, straightforward. Sampling protocols are routinely designed for monitoring invertebrate populations, but measuring trophic connections can be difficult. It is not always possible to track interactions by direct observation, especially when observing small or elusive animals with cryptic behaviors. Monoclonal antibodies have the capacity of elucidating the structure of arthropod food webs, and utilizing a recently developed monoclonal antibody to the HWA (Harwood & Rieske-Kinney, unpublished), we plan to employ this innovative approach to examine the structure of adelgid food webs in hemlock forests in eastern Kentucky. This study will be the first examining the structure of these food webs, and will utilize state-of-the-art immunoassay technology. An understanding of these interaction pathways will subsequently enable the development of management recommendations for biological control of this invasive pest, thereby minimizing its impacts on our hemlock resources. Technical Narrative -----_.~._------ ..._-- Introduction and Expected significance of the work: Given pressing concerns over insecticide use in managed and unmanaged ecosystems, conservation biological control and the enhancement of natural enemy populations have become increasingly attractive options that could provide sufficient and sustainable levels of natural control. Although chemical insecticides are often efficient and cost-effective in the short term, they are not a long-term option due to pest resistance, nontarget concerns, and environmental contamination, rendering such systems unsustainable (Pimentel 1995). Conservation biological control through the enhancement of endemic natural enemies is particularly useful in systems tolerant to limited amounts of pest damage. Parasitoids and pathogens both have the potential to affect prey densities, but an assemblage of predators can be equally effective in regulating pest populations. A diverse natural enemy complex may promote stability within certain habitats, but predators often experience large temporal changes in density and diversity. Therefore biological control by individual predators (or guilds of closely related predators) may not stabilize pest densities. However, a community of predators with variable hunting strategies and spatial and temporal variability may have an additive effect, and despite population fluctuations of constituent components of this assemblage, ultimate levels of pest consumption may be sufficient to restrict, or delay, rapid increases in prey populations. Although there are selected examples where individual generalist predators limit the population of their prey, they are present in the agroecosystem as part of an assemblage (Sunderland et a/. 1997). While specialists tend to show numerical responses to changes in prey density, generalist predators are thought to respond less strongly to numerical changes which could restrict their ability to exert control (Hassell & May 1986). A complex of these predators could exert sufficient pressure to be