Monday, December 10, 2007 - 10:29 AM

Assessment of imidacloprid and horticultural oil treatments on predators sssociated with eastern hemlock, Tsuga canadensis

Abdul Hakeem, ahakeem@utk.edu1, Jerome Grant, jgrant@utk.edu1, P. L. Lambdin, plambdin@utk.edu1, Frank A. Hale, fahale@utk.edu2, and Rusty Rhea3. (1) University of Tennessee, Entomology and Plant Pathology, 2431 Joe Johnson Drive, 205 Ellington Plant Sciences Building, Knoxville, TN, (2) University of Tennessee, Plant and Pest Diagnostic Center, 5201 Marchant Dr, Nashville, TN, (3) USDA Forest Service, Forest Health Protection, 200 Weaver Boulevard, Asheville, NC

Various chemical pesticides are used to reduce populations of hemlock woolly adelgid, Adelges tsugae Annand. However, these chemical pesticides may be poisonous to generalist predators as well as to pests. A rich complex of herbivores and predators is associated with eastern hemlock, Tsuga canadensis (L.) Carriere. While herbivores are exposed to imidacloprid through feeding on treated hemlock, predators feeding on these herbivores may be exposed indirectly to imidacloprid. A study was initiated at Indian Boundary in the Cherokee National Forest in Southern Tennessee in Fall 2005 to: 1) ascertain the impact of imidacloprid used against hemlock woolly adelgid on the predatory guild associated with eastern hemlock, 2) determine the diversity and seasonal abundance of the predatory guild on eastern hemlock, and 3) assess influence of vertical stratification on predator composition with emphasis on the spider community. Eastern hemlock trees were either designated as control trees or treated with one of four chemical treatments (soil drench, soil injection, or tree injection and horticultural oil foliar spray). Each of the five treatments was applied in Fall 2005 and Spring 2006. Sampling was conducted monthly from November 2005 to June 2007. On each sample date, one beat-sheet sample was taken in each cardinal direction and direct observation/vacuuming of the main trunk was conducted for 15 minutes. Predators collected and taken to the laboratory for processing and identification. Preliminary results indicated that predators were most affected by soil drench, tree injection, soil injection and horticultural oil, respectively. Identification of spiders and other predators is in progress.

Species 1: Hemiptera Agelgidae Adelges tsugae (hemlock woolly adelgid)