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Finding a Better Control for Fusarium Root Rot in Douglas Fir

PULLMAN, Wash. — For decades, the conifer seedling nursery industry has fumigated soils with the chemical methyl bromide between plantings in order to control a devastating pathogen, Fusarium root rot. Because of safety and environmental concerns, methyl bromide use is increasingly restricted and expensive, and ultimately its use will be phased out.

Thanks to a U.S. Department of Agriculture grant, Washington State University researchers will be developing effective alternatives to controlling Fusarium in Douglas fir nursery seedlings. The nearly $700,000 grant to WSU’s Center for Sustaining Agriculture and Natural Resources from USDA’s National Institute of Food and Agriculture will enable scientists to test the effectiveness of plant-based soil amendments in controlling the disease over the next three years. Researchers will share their results and help growers adopt new control approaches as part of the grant.

The grant will also enable the researchers to develop a faster, more accurate and reliable method to test for and monitor the presence of pathogenic forms of Fusarium. The improved test will allow the scientists to quickly assess the fumigant alternatives and develop a reliable alternative disease control protocol.

“There are several alternative soil treatments that are very promising, but they are understudied,” according to WSU plant pathologist Gary Chastagner, a principle investigator on the research. “We will continue current trials of brassicaceous green plant manures, seed meals, and other soil amendments to develop and effective alternative treatment.”

CSANR BIOAg research leader Lynne Carpenter-Boggs, also a principle investigator on the project, said that the results will provide a safer, less toxic alternative for nursery operators — and a benefit to their pocketbooks.

“Identifying an effective alternative will end the use of methyl bromide on more than 1,000 acres of conifer nursery stock, and save growers more than a million dollars annually,” she said.

Washington state nurseries produce more than 80 million seedlings annually, and in non-fumigated fields the fungal disease can result in more than half of the seedlings needing to be culled. Restrictions on methyl bromide use have driven the cost of fumigation to roughly $2,000 per acre. Despite increasing costs, most nurseries currently fumigate with methyl bromide between every planting as an insurance policy.

NIFA is the new name of the USDA organization formerly known as Cooperative State Research, Education, and Extension Service.


Media Contacts

Lynne Carpenter-Boggs, WSU Center for Sustaining Agriculture and Natural Resources, 509-335-1553
Gary Chastagner, WSU Plant Pathologist, 253-445-4528