Evaluating prey suitability and phenology of two Leucopis species (Dipetera: Chamaemyiidae), potential biological control agents of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae)

Two species of chamaemyiid flies, Leucopis argenticollis Zetterstedt and Leucopis atrifacies (Aldrich) have been collected from western hemlock trees, Tsuga heterophylla (Raf.) Sargent, infested with hemlock woolly adelgid (Adelges tsugae) in the Pacific Northwest. A. tsugae is a destructive introduced pest of hemlock trees in eastern North America, and management has focused on the use of natural enemies through classical biological control. Leucopis spp. found associated with A. tsugae in the Pacific Northwest are known to be important predators of Adelgidae. Additionally, biological control programs for other adelgid pests have employed chamaemyiid predators in the past with varying degrees of success, indicating that L. argenticollis and L. atrifacies are good candidates for biological control of A. tsugae in eastern North America.

This study was conducted to determine the degree of host specificity of both Leucopis spp. by evaluating prey suitability and host acceptance in no choice tests using four adelgid species. Additionally, western hemlock trees infested with A. tsugae are currently being sampled every 2-4 weeks from 14 locations in Washington and Oregon to evaluate seasonal abundance and synchrony of Leucopis spp. with A. tsugae in the field. These studies should help to determine the feasibility of using either of these Leucopis spp. for biological control of A. tsugae.