Symptoms of Powdery Mildew of Southern Peas
Powdery mildew affects a litany of other crops. In the case of southern peas with powdery mildew, the fungus Erysiphe polygoni is the culprit. This fungus appears as a tell-tale light gray to almost white powdery growth on the surface of leaves, pods, and occasionally the stems of the plant. New plant growth becomes contorted, dwarfed, and may yellow and drop. Pods are twisted and stunted. As the disease progresses, the entire plant may turn yellow and defoliate. Powdery mildew of southern peas is most common on older leaves and stems. The talc-like powdery mildew is made up of spores that are blown by the wind to infect nearby plants. As severe infections defoliate beans, yield reduction is reduced. The pods that do form develop purplish spotting and become distorted, thus unsalable. For commercial growers, this infection can be a huge economic loss. Powdery mildew reproduces during dry spells, although increased humidity increases the severity of the disease and periods of heavy dew foster infections. Not to be confused with downy mildew, powdery mildew does become severe during periods of low rainfall. Although the fungus is thought to survive on wild cucurbit and other weeds, no one really knows how it survives between crop seasons.
Southern Pea Powdery Mildew Control
Spray or dust with sulfur according to the manufacturer’s instructions once an infection of powdery mildew has been observed amongst the southern peas. Apply sulfur at 10 to 14 day intervals. Do not apply when temperatures exceed 90 degrees F. (32 C.) or on young plants. Otherwise, powdery mildew is best managed through cultural practices. If available, select resistant cultivars for planting. Only plant certified seed that has been treated with a fungicide. Practice crop rotation. Plant southern peas in a well-draining area and only water at the base of the plants. Post-harvest, remove crop debris that may harbor the fungus and allow it to overwinter.
