Effect of phosphate treatments on sudden oak death in tanoak and Shreve's oak

Abstract

Field experiments were conducted to evaluate the effectiveness of phosphonate chemical treatments for control of sudden oak death in tanoak (Lithocarpus densiflorus) and Shreve's oak (Quercus parvula var. Shrevei). Native stands of mature trees were preventatively treated with Agrifos® systemic fungicide and subsequently infected with Pytophthora ramorum. Both injection treatments as well as topical application of Agrifos® with Pentrabark® surfactant were evaluated. Experimental methods were designed to test both within tree and between tree variability. Leaves and wood samples were also collected from the treated trees for chemical analysis of phosphonate levels. The injection and topical phosphonate treatments significantly reduced lesion size in tanoaks and Shreve’s oaks compared to untreated control trees. However, the extent of moss covering the tree trunk affected the Shreve’s oaks topical treatment. A combined treatment of injection and topical application methods was found to be most effective in Shreve’s oak. The results suggest that the dosage of phosphonate that is successfully introduced into the tree may be as important as the application method. In addition, the range of resistance and susceptibility to P. ramorum that exists in native stands may affect the success of phosphonate treatments.

Parent Publication

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

Citation

Schmidt, Doug; Garbelotto, Matteo; Chambers, Dave; Tjosvold, Steve. 2006. Effect of phosphate treatments on sudden oak death in tanoak and Shreve''s oak. 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: 263