Foliar Diseases of Peanuts
Early and late leaf spot are the most destructive diseases of peanut in Alabama. For decades, peanut harvesting in Alabama started when all the peanuts in a field were stripped of their leaves by one or both of these diseases. Improved disease control in the early 1970s, which came with the availability of much more effective leaf spot fungicides, resulted in sizable gains in pod yield and quality. Depending on weather conditions, annual losses to early and late leaf spot still range between 5 and 10 percent of Alabama's total peanut crop. In isolated fields, failure to control one or both of these diseases can reduce expected pod yields by 20 to 30 percent.
Peanut rust, caused by Puccinia arachidis, occurs sporadically on peanut in Alabama. Widespread use of chlorothalonil fungicides has kept problems with peanut rust to a minimum. Left uncontrolled, peanut rust can be equally as destructive as leaf spot diseases can. Outbreaks of this disease are most likely to be seen beginning in late July to early August in Covington, Geneva, and Houston counties. Recently, severe rust-related plant death and yield loss was observed on Virginia-type peanuts in Baldwin County.