Fungicide efficacy for control of anthracnose of dry bean in Ontario

Dry bean anthracnose, caused by Colletotrichum lindemuthianum, is a devastating disease affecting seed quality and yield of a dry bean (Phaseolus vulgaris L.) crop. A multiple-year inoculated field study near Exeter, Ontario examined commercially available chemical control methods for anthracnose control in susceptible dry bean cultivars. Fungicides were applied at first flower and 14 days later; leaves, stems, and pods were evaluated for disease incidence and severity. Upon maturity, plots were harvested, and the grain threshed and weighed to determine grain yield, as well as pick and seed weight. Under moderate to severe disease infection levels, the strobilurin fungicides (alone and in combinations), fluazinam, and thiophanate-methyl had the greatest reduction in disease severity, and subsequently greater seed yield, lower pick, and larger seed size compared to the inoculated control. Profit margins were greatest for the strobilurins, fluazinam, and thiophanate-methyl, while metconazole and fluopyram alone and with prothioconazole were similar to or slightly greater than the inoculated control. These results provide key information to growers as to which fungicides should be selected to maximize yield and profitability in dry bean under severe anthracnose pressure.