Fungus on Pea Pods

Many types of peas have sweet, edible pods.

Peas are a sweet and healthy addition to the home garden. They are susceptible to fungal infection and one of the most common is powdery mildew. Affecting all above ground parts of the plant, powdery mildew can be devastating to your pea harvest. Cultural methods can help you control and prevent powdery mildew on pea pods.

Symptoms

Powdery mildew initially causes white, powdery spots on leaves. As the fungus grows entire leaves and stems can be engulfed by the fungus. According to the University of California extension service, fruit is not generally infected by the fungus, but pea pods may get brown spots. Infected leaves may eventually yellow and drop from the plant. Leaf loss can expose peas to sun and other elements and can weaken the plant, reducing yields.

Causes

There are several factors that lead to a powdery mildew outbreak. Some varieties of pea will be more susceptible than others and plants that aren't in optimal health can also be more susceptible. Hot, humid weather helps to spread the fungus. Humidity usually comes from overcrowded plantings and irrigation practices that leave foliage and fruit wet. Plants should only be watered at the base.

Disease Cycle

The powdery fungus you see on leaves is actually a living mat of fungal spores. These spores require living tissue in order to thrive and will often overwinter on weed hosts when their regular hosts die. In spring, when peas are replanted the fungus can spread back to this preferred host. Humidity is generally required for germination but the spores themselves are spread by wind. Direct sunlight and hot temperatures can inhibit germination and kill the fungus.

Control

Reducing overcrowding and allowing airflow to your peas is the easiest way to prevent and cure powdery mildew. Thin your plantings to allow sunlight to all parts of the plant. Overhead watering can help wash off the fungus, but, according to the University of California, this irrigation method can cause issues with other pests and diseases. Fungicides are available for powdery mildew. They must be applied as soon as symptoms present themselves and are not recommended for organic gardening.

References

• UC IPM Online; Powdery Mildew on Vegetables; R. M. Davis, W. D. Gubler, S. T. Koike
• Colorado State University Extension; Powdery Mildews; B. Edmunds, L.P. Pottorff; May, 2009