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Anthracnose (Colletotrichum lindemuthianum) on White Bean (Phaseolus vulgaris L.) in Southern Ontario: Spread of the Disease from an Infection Focus. J. C. Tu, Plant Pathologist, Research Station, Research Branch, Agriculture Canada, Harrow, Ontario N0R 1G0. Plant Dis. 65:477-480. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-477.

Spread of anthracnose (Colletotrichum lindemuthianum, delta race) from an initial infection focus was studied in 1978 and 1979 in field plots planted with a susceptible white bean cultivar (Phaseolus vulgaris ‘Fleetwood’). Splashing rain spread the disease for short distances, although some plants adjacent to diseased plants did not become infected. Long-distance spread, 3–4.6 m per rainstorm, was caused by splashing raindrops blown by gusting winds. Disease spread from the infection focus toward the northeastern quarter of plot followed the direction of prevailing winds. Disease severity was highest at or near the axis of the sector nearest the initial infection focus and decreased gradually toward the periphery of the sector. The fungus required about 10 mm of rain to establish infection. In southern Ontario, temperature was not a limiting factor for infection and disease spread, but temperatures above 25 C appeared to restrict disease development.