One of the more common diseases of lima beans is called pod blight of lima beans. Pod blight in lima bean plants can cause serious losses in yield. What causes this lima bean disease and what methods of control are there for lime bean blight?
Symptoms of Pod Blight in Lima Bean Plants
Symptoms of pod blight of lima beans first manifests as irregular, brown eruptions on fallen petioles in mid-season, and on pods and stems close to maturity. These small, raised pustules are called pycnidia and in wet seasons may cover the entire plant. The upper portions of the plant may yellow and die. Seeds that have become infected may look completely normal or will crack, shrivel and become moldy. Infected seeds often do not germinate.
Symptoms of this lima bean disease may be confused with those of anthracnose, as both of these diseases of lima beans occur late in the season.
Conditions Favorable for Lima Bean Blight
Pod blight is caused by the fungus Diaporthe phaseolorum, which overwinters in infested crop detritus and in infected seeds. Spores are transferred to plants via wind or splashed water. Thus, although infection can occur throughout the season, this fungus thrives in wet, warm conditions.
Pod Blight Control
Since the disease overwinters in crop detritus, practice good garden sanitation and clear the beds of any lingering crop debris. Remove any weeds that may also harbor the disease.
Only use seed that is grown in the western United States and use a high quality disease free seed. Do not save seed from the previous year if the disease was evident in the crop. Rotate the crop with non-host crops on a 2 year rotation.
Using a copper-type fungicide on a regular basis will help control the disease.