Symptomatology and Ecology of Alfalfa Anthracnose in Oklahoma. S. J. Allen, Former Graduate Research Assistant, Department of Agronomy, Oklahoma State University, Stillwater 74078. G. L. Barnes, Professor, Department of Plant Pathology, and J. L. Caddel, Associate Professor, Department of Agronomy, Oklahoma State University, Stillwater 74078. Plant Dis. 69:248-251. Accepted for publication 17 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-248.

A study was conducted in Oklahoma to determine if occurrence of alfalfa anthracnose symptoms are linked to varying yearly temperature and precipitation patterns and to determine when the causal agent (Colletotrichum trifolii) is present in stands of alfalfa (Medicago sativa). Data from five sites were compared with weather patterns over a 3-yr period. Yearly variation in amount and distribution of precipitation affected occurrence of symptom development. C. trifolii appears to be present in alfalfa stands throughout the growing season. Anthracnose damage occurs periodically in Oklahoma when weather patterns are favorable, and resistance to C. trifolii is an important consideration in cultivar development for the state.