Evaluation of fungicides for use against P. ramorum

The Forest Service, Washington State Pesticide Commission, Pacific Northwest Christmas Tree Association, IR-4 program, and the WSDA Nursery Research Program are supporting research at WSU Puyallup to determine the effectiveness of various fungicides in protecting conifers and rhododendrons from infection by this pathogen. This work has shown that several traditional contact materials, such as mancozeb, and the systemic material Subdue MAXX, have the potential to provide excellent control of diseases caused by P. ramorum. However, growers and regulatory agencies are concerned that the use of fungicides may be masking symptom development, thus making it harder to prevent the spread of this pathogen on infected nursery stock. Additional studies will be conducted at the National Ornamentals Research Site at Dominican University, California (NORS-DUC) to determine the residual effectiveness of fungicides and determine if any of them have the potential to mask symptom development on infected plants.