title: Introduced and Native Parasitoid Wasps Associated With Larch Casebearer (Lepidoptera: Coleophoridae) in Western Larch.
abstract: The larch casebearer [Coleophora laricella (Hubner)], a non-native insect, continues to impact western larch (Larix occidentalis Nutt.) through defoliation events in the Pacific Northwest. Biological control programs starting in the 1960s released seven species of parasitoid wasps to control C. laricella outbreaks. However, information about current population dynamics of C. laricella and associated parasitoids remains lacking. Therefore, the goal of this study was to document the presence, current distributions, densities, and parasitism rates of introduced and native parasitoid wasps occurring on C. laricella throughout the Northwestern U.S. range of L. occidentalis. We sampled L. occidentalis trees at multiple sites in Oregon, Washington, Idaho, and Montana. C. laricella was present at all sites with average state densities ranging from 6.2 to 13.1 moths/100 buds. We recovered two introduced hymenopteran biological control agents; Agathis pumila (Ratzeburg: Braconidae) at 79% of the sites, and Chrysocharis laricinellae (Ratzeburg: Eulophidae) at 63% of the sites. Fourteen species of native parasitic wasps were also recovered. The most common species were: Bracon sp., Spilochalcis albifrons, and Mesopolobus sp. The average native species parasitism rate across the four states was 9.0%, which was higher than the introduced species Ch. laricinellae (2.9%), but not as high as A. pumila (19.3%). While survey results suggest that native species may be more important for the control of C. laricella than previously thought, A. pumila remains the major source of regional control. However, further research is needed to better understand how introduced and native parasitoids interact to control invasive pest populations.
authors: School of Biological Science, Washington State University-Vancouver, 14204 NE Salmon Creek Avenue, Vancouver, WA 98686. m.miller-pierce@email.wsu.edu.
authors: M
authors: M
authors: Miller-Pierce
authors: Department of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, OR 97331.
authors: D C
authors: DC
authors: Shaw
authors: Department of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, OR 97331.
authors: A
authors: A
authors: Demarco
authors: Department of Forest Ecosystems and Society, OSU Extension Service, 10507 N. McAlister Road, La Grande, OR 97850.
authors: P T
authors: PT
authors: Oester
mesh_terms: D000818:Animals; D058865:Introduced Species; D028221:Larix / Q000469:parasitology*; D007814:Larva / Q000469:parasitology; D009036:Moths / Q000469:parasitology*; D010572:Pest Control, Biological; D014481:United States; D014863:Wasps / Q000502:physiology*
keywords: Agathis pumila; Coleophora laricella; Larix occidentalis; biological control; parasitoid