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Disease Note.

Occurrence of Macrophomina phaseolina on Canola in Indiana and Kentucky. R. E. Baird, Purdue University, SWPAP, RR6 Box 139A, Vincennes, IN 47591 D. E. Hershman, University of Kentucky, UKREC, P.O. Box 469, Princeton 42445 and E. P. Christmas, Agronomy Department, Purdue University, West Lafayette, IN 47907. D.E. Hershman, University of Kentucky, UKREC, P.O Box 469, Princeton 42445, and E.P Christmas, Agronomy Department, Purdue University, West Lafayette, IN 47907. Plant Dis. 78:316. Accepted for publication 1 November 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0316D.

Canola (Brassica napus L. ‘Ceres’) grown on a Lyles fine sand loam near Vincennes, Indiana, was found to be prematurely senescing or killed during early-mid grain fill in 1993. A commercial crop of cv. Capricorn grown in a field near Schochoh, Kentucky, exhibited similar symptoms in 1991. In both years, symptoms developed under conditions of adequate soil moisture but temperatures were 5-10 degrees above normal (32-36 C). Affected plants at both locations had a high incidence of infection by Sclerotinia sclerotiorum (Lib.) de Bary, but 10-15% of the plants contained microsclerotia in the taproots, and the affected tissue was shredded. Macrophomina phaseolina (Tassi) Goidanich was isolated from the affected tissues on potato-dextrose agar. This pathogen has been reported previously to occur in Brassica rapa L. in California (1). The involvement of M. phaseolina in premature senescence and death of canola in Indiana and Kentucky has not been established. Preliminary studies in a growth chamber at 23-26 C, using soil infested with cornmeal-sand inoculum of M. phaseolina or crown inoculations of the fungus, were not successful. However, the frequent isolation of the pathogen from prematurely senescing and dead plants indicates the need for further study to confirm its involvement in premature senescence of canola.

Reference: (1) A. Ghaffar and G. A. Zenlmeter. Plant Dis. Rep. 52:223, 1968.