Suppression of Phytophthora ramorum infestations through silvicultural treatment in California's north coast

Abstract

In 2006, three forested sites infested with Phytophthora ramorum in Humboldt County, California were subjected to different combinations of treatments designed to reduce inoculum and control spread. One treatment, consisting of removal of all California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) trees, was applied at all three sites, and other treatments were applied as case studies at single sites. The sites were monitored for 6 years. Results to date suggest that the treatments that involved the cutting of California bay laurel and tanoak substantially reduced P. ramorum inoculum levels. However, in treatment areas where scattered California bay laurel trees were inadvertently missed because of a restricted time window for operations, a relatively minor component of residual California bay laurel trees may have become infected following treatment and/or harbored prior cryptic infections and subsequently spread P. ramorum to regenerating California bay laurel and tanoak. The data suggest that pathogen reestablishment in these sites was driven by both incomplete treatment application and spread from adjacent, untreated stands.

Parent Publication

• Proceedings of the sudden oak death fifth science symposium

Citation

Valachovic, Yana; Lee, Chris; Twieg, Brendan; Rizzo, David; Cobb, Richard; Glebocki, Radoslaw. 2013. Suppression of Phytophthora ramorum infestations through silvicultural treatment in California's north coast. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 108-113.