Analyzing the Impact of Imidacloprid on Soil Interstitial Organisms in Eastern Hemlock Trees at the Great Smoky Mountain National Park


Search abstracts:

Caitlin Bennett
Committee: Paul Bartels, Alisa Hove, Steve Cartier

For the past 50 years the native range of the Eastern Hemlock extending from Maine to Georgi has have been under attack by the woolly adelgid (an evasive aphid-like species from Asia) which feeds on the sap of the tree. High infestation and mortality rates have permanently changed the forestry landscape of the eastern United States. First identified in Virginia in 1951, the Hemlock Wooly Adelgid (referred to as the HWA) has spread both northward, westward and to the south where its presence in the Great Smoky Mountain National Park (GSMNP) was confirmed in 2002. Today the devastation caused by the HWA is recognized as the most significant threat to the eastern forest and associated habitat. Symptoms of prolonged infestation included visible results such as thinned canopies (needles going gray), limb loss and eventually dieback if left untreated. Imidacloprid, a systemic neonicotinoid insecticide used by the US Forestry Service has proven to be a useful and effective tool in the GSMNP to manage the woolly adelgid. While several studies have demonstrated the efficacy of imidacloprid in reducing adelgid populations, few have examined the long term affects that it might have on the environment and ecosystems. The GSMNP is known as one of the most biodiverse temperate forest in the world, but the parks micro-biota is relatively unknown. This study assessed the potential impact of Imidacloprid treatments on non-targeted micro-fauna located in the leaf litter and shallow soils beneath treated hemlock trees. Specifically microfauna populations were evaluated within two treated areas of the GSMNP (Big Creek Campground and Leather Wood Conservation) and compared to a non-treated area of the park (Chestnut Bridge Trail). A total of 60 soil samples were collected; 20 from each of the treated locations and 20 from trees that remained untreated. In the laboratory, specimens from each soil /leaf litter sample were isolation and processed via Ludox®AM centrification and preserved in boiling alcohol. Based on a microscopic observation and the conduction of a Kruskal–Wallis test, the supernatant from each sample indicates that no significant differences between microfuna populations were found were observed between the treated and untreated trees. These results generally suggest that there are no significant negative affects to the microfauna present in the substrata from the current use of Imidacloprid in the GSMNP.