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Effect of Foliar Infection Caused by Colletotrichum coccodes on Yield of Russet Burbank Potato. D. A. JOHNSON, Plant Pathologist, Department of Plant Pathology, Washington State University, Pullman 99164. Plant Dis. 78:1075-1078. Accepted for publication 27 July 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1075.

The effect of foliar infection by Colletotrichum coccodes on yield of Russet Burbank potato was investigated in the greenhouse and field. Foliage of plants in both the greenhouse and field was wounded with sterile sand blown from a sandblaster before inoculation with a spore suspension of C. coccodes. In two experiments in the greenhouse, total yield was significantly reduced by 32 and 19% and mean tuber weight was significantly reduced by 29 and 43%, respectively. In the field, total tuber weight was significantly reduced by 7% in 1991, 12% in 1992, and 11% in 1993. Weights of potatoes graded U.S. No. 1 were significantly reduced by 12% in 1991, 18% in 1992, and 16% in 1993. The number of No. I tubers per plant was significantly reduced in the field. Specific gravity was not reduced. Sandblasting by itself did not affect yield.