As plants begin to bloom, sulfur or chlorothalonil can be sprayed weekly on snap and green beans only. Wait seven days between spraying and harvest when using chlorothalonil. Apply chemicals according to directions on the label. The stems, leaves and fruits of bean plants can be infected by either disease. Rain and damp weather favor disease development.
Halo blight occurs primarily when temperatures are cool.
Light greenish-yellow circles that look like halos form around a brown spot or lesion on the plant. With age, the lesions may join together as the leaf turns yellow and slowly dies. Stem lesions appear as long, reddish spots. Leaves infected with common blight turn brown and drop quickly from the plant. Common blight infected pods do not have the greenish-yellow halo around the infected spot or lesion.