Monday, December 11, 2006

Established predators of Fiorinia externa Ferris (Hemiptera: Diaspididae) on eastern hemlock, Tsuga canadensis (L.) Carriere, in urban and forest sites

C. A. Lynch, clynch3@utk.edu1, P. L. Lambdin, plambdin@utk.edu2, J. F. Grant, jgrant@utk.edu2, Rusty Rhea3, and R. Reardon4. (1) University of Tennessee, Department of Entomology & Plant Pathology, 2431 Joe Johnson Drive, 205 Ellington Plant Sci. Bldg, Knoxville, Tennessee, (2) University of Tennessee, Entomology and Plant Pathology, 2431 Joe Johnson Drive, 205 Ellington Plant Sciences Building, Knoxville, TN, (3) USDA Forest Service, Forest Health Protection, 200 Weaver Boulevard, Asheville, NC, (4) USDA Forest Service, Forest Health Technology Enterprise Team, 180 Canfield Street, Morgantown, WV

A project was initiated in September 2004 to determine the indigenous predators of Fiorinia externa Ferris, elongate hemlock scale, and their impact on pest populations. Branch samples were taken monthly from four sites (two forest and two urban) in eastern Tennessee and western North Carolina to assess predator field damage from October 2004 to April 2006. Predators of the exotic scale were collected from beat sheet samples from September 2004 to May 2006. Laboratory tests were conducted on field collected coccinellid and neuropteran predators to assess food consumption among predators of elongate hemlock scale. From field samples, the mean predator damage for the four sample sites was 8.28% with a range of 4.72 to 9.84 percent. Field predator damage varied by season within each of the sites. There were 312 total adult predators, and 150 larvae collected from September 2004 through May 2006. The highest numbers of specimens and species were collected from May through October in 2005. Six predaceous species (Chilocorus stigma (Say), Conwentzia pineticola Enderlein, Harmonia axyridis (Pallas), Rhyzobius lophanthae (Blaisdell), Scymnillus horni Gordon, and Scymnus loweii Mulsant) were documented to feed on elongate hemlock scale during no choice tests. Chilocorus stigma, R. lophanthae, and S. horni had the highest feeding rates, respectively. For immature and adult scales eaten, C. stigma and R. lophanthae consumed more than the other four species. At heavily infested sites, a combination of these coccinellids could potentially be used to significantly reduce elongate hemlock scale populations in forests or urban landscapes.

Species 1: Coleoptera Coccinellidae Chilocorus stigma (twice-stabbed ladybeetle)
Species 2: Coleoptera Coccinellidae Rhyzobius lophanthae
Species 3: Coleoptera Coccinellidae Scymnillus horni