Predators collected from balsam woolly adelgid and Cooley spruce gall adelgid in western Oregon and Washington, U.S.A., with reference to biological control of hemlock woolly adelgid (Hemiptera: Adelgidae)

Abstract

As part of a comprehensive study to survey predators associated with hemlock woolly adelgid, Adelges tsugae Annand, 1928 in the Pacific Northwest (PNW), U.S.A. (Kohler et al. 2008), predators of balsam woolly adelgid, Adelges piceae (Ratzeburg, 1844) and Cooley spruce gall adelgid, Adelges cooleyi (Gillette, 1907) (all Hemiptera: Adelgidae) were sampled on nine dates from June 2005 to October 2006 on a small number of trees. Samples were collected every 6–8 weeks. Predators were collected from two A. piceae infested grand fir, Abies grandis (Douglas ex David Don) Lindley, and one A. cooleyi infested Engelmann spruce, Piceae engelmanii Parry ex Engelmann, on the Oregon State University campus in Corvallis, Oregon, and two A. cooleyi infested Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco (all Pinaceae). One Douglas-fir was an ornamental tree in Corvallis, Oregon and the other was in a seed orchard on Whidbey Island, Washington. Adelges cooleyi predators were collected by striking an infested branch four times over a plastic tub with an area of 0.16 m2. Adelges piceae predators were collected by brushing adelgid wool on the bole of infested trees with a 2-inch wide paintbrush over a beat sheet. Predators were collected from the tub and beat sheet with an aspirator. Adult insects were killed in a sealed 9-dram plastic vial containing a small piece of Hot Shot No-Pest Insecticide Strip (Spectrum Brands Inc., Atlanta, Georgia). Immature insects were killed in KAAD mixture (10 parts 95% ethanol, 1 part kerosene, 2 parts glacial acetic acid, and 1 part dioxane) and preserved in 70% ethanol (Borrer et al. 1989). Adult specimens were identifi ed either by taxonomic specialists or by comparison to previously identified museum specimens. Voucher specimens were deposited in the Oregon State Arthropod Collection, Department of Zoology, Oregon State University, Corvallis, Oregon.