Burning to Reduce Sclerotia of Sclerotinia sclerotiorum in Alfalfa Seed Fields of Southeastern Washington. R. G. Gilbert, Research Plant Pathologist, Vegetable and Forage Crop Production, U.S. Department of Agriculture, Agricultural Research Service, Prosser, WA 99350. Plant Dis. 75:141-142. Accepted for publication 3 July 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/PD-75-0141.

Fall burning produced an intense surface fire that reduced numbers of sclerotia in an alfalfa seed field by >95%. The fire killed sclerotia in the dense layer of surface plant residue and scorched and killed sclerotia in the surface soil (0–2 cm). Only 14% of the collected surface soil sclerotia were viable after the fall burn. During the next 6 mo, the detectable number of sclerotia in surface soil samples declined from 246/m² in November to 7/m² in May and viability of sclerotia declined from 12 to 0%, respectively. Winter burning reduced surface residue and numbers of sclerotia but had no detectable effect in reducing the viability and survival of surface soil sclerotia. Spring mowing of the plant canopy did not reduce numbers of sclerotia nor influence the survival and viability of sclerotia. Alfalfa seed yields were 43 and 13% greater following fall burn and spring mowing treatments, respectively, than following the standard practice of winter burning.

Keyword(s): Medicago sativa.