VIEW ARTICLE

Ecology and Epidemiology

Root-Colonizing Insects Recovered from Douglas-Fir in Various Stages of Decline Due to Black-Stain Root Disease. J. J. Witcosky, Graduate research assistant, Department of Entomology, Oregon State University, Corvallis 97331; E. M. Hansen, Associate professor, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. Phytopathology 75:399-402. Accepted for publication 13 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-399.

Douglas-fir (Pseudotsuga menziesii) trees infected with Verticicladiella wageneri were assigned to one of five symptom classes by crown color and terminal growth characteristics at three widely separated sites in the Coast Range of Oregon. Root systems of trees in each symptom class were excavated, and the insects beneath the bark were collected. Two weevils, Steremnius carinatus and Pissodes fasciatus, and the root bark beetle Hylastes nigrinus were commonly associated with diseased trees. Insects sequentially colonized roots of diseased trees as each root succumbed to infection; the colonization period generally lasted from 2 to 4 yr. The occurrence of these root-colonizing insects throughout the decline of the host suggests that S. carinatus, P. fasciatus, and H. nigrinus may act as vectors of V. wageneri in this ecosystem.