TAKE ONE
Gardener News Serving the Agricultural, Gardening and Landscaping Communities
September, 2017
GARDENERNEWS.COM
TAKE ONE No. 173
“Good-Guy” Fungus to Take on Killer of Oaks and Ornamental Crops
Discoloration on an oak tree trunk caused by Phytophthora ramorum. By Jan Suszkiw ARS Office of Communications
A beneficial soil fungus could offer a biobased approach to battling Phytophthora ramorum, a pathogen that kills oaks, other tree species and woody
ornamentals. Viewed through a microscope, the fungus Trichoderma asperellum resembles little more than delicate branched filaments. But make no mistake; it is a formidable hunter—of other microorganisms, that is.
Since 2006, Agricultural Research Service (ARS) plant pathologist Tim Widmer and colleagues have conducted laboratory and field tests to gauge T. asperellum’s potential to biologically control Phytophthora ramorum. A
Joseph O’Brien, USDA Forest Service/Photo
plant pathogen, P. ramorum is the culprit behind sudden oak death, a disease of oak and other hardwood trees in coastal forests of California and Oregon. Nursery growers are familiar with a different manifestation of P. ramorum,
known as “ramorum blight.” The disease afflicts rhododendron, viburnum, camellia, and other woody ornamental plants. Chemical fumigation and soil sterilization are two common methods of keeping (Cont. on page 20)