WIFDWC - 2000

DISEASE CONTROL COMMITTEE REPORT

R.L. James
Chairperson

The Disease Control Committee met on Tuesday, August 15. Although only a few people were in attendance, discussions were lively and informative. Most discussions centered around forest nursery pathogens, including Botrytis cinerea and Fusarium spp. Discussions included ways of controlling these important pathogens using chemical and non-chemical treatments. Examples include treating conifer seeds with benomyl and other fungicides to control seed-borne Fusarium diseases and using pre-plant solarization treatments instead of chemical fumigation to reduce levels of soil-borne pathogens. Although alternatives to methyl bromide have not been developed for all bareroot forest nurseries, some potential alternatives showing promise include bare fallowing (with periodic soil cultivation) for at least one year prior to sowing and alternative chemical fumigants using chloropicrin, TeloneÒ, and dazomet. Other tested alternatives such as organic soil amendments, different green manure crops, and solarization have usually not been as effective. Efforts during the next few years will continue to fine tune alternative treatments to the needs of individual nurseries.

Concern was voiced by Terry Shaw (from long distance) about some of the “quack” treatments that are currently being implemented to control some important tree diseases. His examples include using unproven remedies to treatdeclining oaks in Marin County, California (caused by Phytophthora sp.) and conifers infected with Armillaria root disease. In the case of Armillaria, he questions the efficacy of using fertilizers to reduce exisiting and potential damage in forest stands and cites the lack of documented data in peer-reviewed publications. Also, in the case of oak decline, apparently some companies are recommending treatments to homeowners without even knowing anything about disease etiology. It is important that disease control methods be rigorously evaluated under different forest, nursery, and environmental conditions before being recommended by professional plant pathologists.