Disease Note

Root Rot (Aphanomyces euteiches) Epidemic in Northern Idaho Spring Peas. R. L. Bowden, Department of Plant, Soil & Entomological Sciences, University of Idaho, Moscow 83843. H. S. Fenwick, and L. J. Smith, Department of Plant, Soil & Entomological Sciences, University of Idaho, Moscow 83843, and J. M. Kraft, USDA-ARS, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350. Plant Dis. 69:451. Accepted for publication 25 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-451c.

Root rot caused by Aphanomyces euteiches Drechs. has been a serious constraint on spring pea (Pisum sativum L.) production in Idaho County in northern Idaho since at least 1943. Growing Austrian winter peas (P. sativum subsp. arvense (L.) Poir.) instead of spring peas has reduced disease severity, and yields usually have been acceptable. Aphanomyces root rot has been rare or absent in other pea production areas of northern Idaho despite the use of short crop rotations. In 1984, after an unusually cool, wet spring, an estimated 1,600 ha (5% of the area planted) of spring peas in Clearwater, Idaho, Latah, Lewis, and Nez Perce counties were severely infected. Diagnosis was confirmed by observation of oospores in roots, method of zoospore release, and pathogenicity tests. Total direct losses were estimated to be at least $350,000.