Impact of Fungicide Seed Treatments on Rhizoctonia Root Rot, Take-all, Eyespot, and Growth of Winter Wheat. R. W. Smiley, Oregon State University, Columbia Basin Agricultural Research Center, P.O. Box 370, Pendleton 97801. D. E. Wilkins and E. L. Klepper. USDA-ARS, Columbia Plateau Conservation Research Center, P.O. Box 370, Pendleton, OR 97801. Plant Dis. 74:782-787. Accepted for publication 23 April 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0782.

Fungicides were examined for in vitro activity against Rhizoctonia solani AG-8 and R. oryzae and for capacity to suppress the incidence and severity of Rhizoctonia root rot of winter wheat in eastern Oregon. Thirteen seed treatments were evaluated at three sites during 1986-87 and five were evaluated at two sites during 1987-88. A factorial experiment with variables of seed treatment and tillage intensity (conventional plowing vs. no tillage) was also performed at two sites. All seed treatments in the seven experiments were ineffective or unreliable for controlling Rhizoctonia root rot. Tolclofos-methyl was highly toxic to both pathogens and strongly reduced the incidence of root rot, but was also phytotoxic. Most of the fungicides reduced the tillering capacity of winter wheat plants, and none of the fungicides consistently improved grain yields. Triadimenol and prochloraz seed treatments strongly reduced the incidence of take-all and eyespot, respectively.