Effects of phosphate treatments on the growth of Phytophthora ramorum in tanoak stems

Abstract

In Oregon, tanoak (Lithocarpus densiflorus) is the tree species most susceptible to Phytophthora ramorum, and Sudden Oak Death (SOD) occurs only in forests where tanoak is present. Oregon is attempting to eradicate the pathogen by complete destruction of host plants in and near infested sites. Although the eradication effort has been successful to a degree, it is clear that we need other tools to limit spread of the pathogen in forests. The purpose of this study is to begin evaluating phosphonate (Agrifos-400®) treatments as tools for managing SOD in Oregon Forests. Phosphonate (Agrifos-400®) treatments have been shown to reduce P. ramorum lesion development in coast live oak and tanoak in California, but the results for tanoak suggest that bark application on tanoak may not be effective (Garbelotto and others 2003). There is little or no information as to whether or not application of phosphonate to the lower bole by any method can reduce infection on the upper stem or foliage, or reduce sporulation on these same parts. The objectives of our study were to: 1) compare the effectiveness of lower bole bark application and trunk injection in terms of lesion development in the lower bole, upper bole, and leaves of tanoak; 2) evaluate the relative effectiveness of a single application of Agrifos® to two applications separated by 3 months; 3) evaluate the relative effectiveness of maximum label rate compared to two times the maximum label rate, and; 4) describe the duration of treatment effect.

Parent Publication

• Proceedings of the sudden oak death second science symposium: the state of our knowledge

Citation

Kanaskie, Alan; Hansen, Everett; Sutton, Wendy. 2006. Effects of phosphate treatments on the growth of Phytophthora ramorum in tanoak stems. In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 259-261