Impacts on Larval Populations of Ephemeroptera, Plecoptera, and Trichoptera in Areas Infested by Hemlock Woolly Adelgid (Hemiptera: Adelgidae) at the Southern Edge of the Range of Eastern Hemlock

Abstract

Abstract Eastern hemlock, Tsuga canadensis (L.) Carriere, is an important component of riparian zones in Appalachian forests. Tree mortality caused by hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae) could impact aquatic macroinvertebrate populations. Our study examined larval populations of Ephemeroptera, Plecoptera, and Trichoptera occurring in the headwaters of two creeks in the Sumter National Forest (Oconee Co., SC). Larval populations were initially sampled in King Creek (2006) and Crane Creek (2007) in separate studies. When those studies were conducted, there was no noticeable decline in hemlock health along either creek. However, by 2009 hemlock mortality along both creeks was obvious, and the Ephemeroptera, Plecoptera, and Trichoptera community was resurveyed on both creeks. This is the first study comparing aquatic macroinvertebrate populations before and after A. tsugae infestation. Ephemeroptera, Plecoptera, and Trichoptera larvae were identified to genus, and analyzed at the functional feeding group level. In both creeks, collector filterers and scrapers were significantly more abundant in the initial survey than in 2009. Generic diversity within each creek was examined using the total Ephemeroptera, Plecoptera and Trichoptera community, and was based on the indices of: richness (D0), Shannon exponential (D1), and inverse Simpson (D2). The only diversity measure that differed significantly between the original survey and 2009 was the Shannon exponential index for Crane Creek which was significantly higher in 2009 than 2006