The humble garden pea (Pisum sativum L.) has appeared on the plates of farmers and beneath their children’s tables for thousands of years. This little green vegetable has endured countless botanical biopsies, genetic tinkering and domestic cultivation since 7000 BC, appearing on every continent of the world as food, fodder and forage. The pea is not without its troubles, however. Its primary enemies are fungal and bacterial diseases, usually caused by over-watering, high humidity or stress from inadequate growing conditions.
Blight, Fungus and Mildew
A myriad of fungal and bacterial diseases plague the garden pea. Most of these types of diseases appear during seasons of high humidity and excessive rain. Downy mildew is one of the most common pea diseases, causing the plant to curl up into stunted, discolored leaves and stems early in the season. Humid conditions cause the fungus to produce fuzzy fruits. Powdery mildew develops later in the growing season as a white powder that coats leaves and stems. Both of these diseases are spread by wind during dry seasons and turn the plant yellow. Myospaerella blight cause purple streaks or lesions on the entire plant, which eventually turns yellow and dies. Leaf and pod spot, caused by a similar bacterium, appear as sunken purple or black spots. Control the spread of disease by rotating crops and burying or burning infected plants. Never place infected crops in the compost for recycling.
Rot and Viruses
Seed rot and root rots are caused by fungi that lie dormant in the soil and strike the pea plant when environmental conditions are favorable. Most fungi prefer very moist soil conditions with warm temperatures and high humidity, but the common and very destructive Fusarium root rot thrives in warm, dry soil. Ascochyta foot rot and Pea streak causes purple lesions and streaks similar to Myospaerella blight, forcing the plant to mature and die rapidly. Control the spread of disease by treating seeds and maturing plants with anti-fungal solutions, crop rotation and sufficient air circulation between growing plants. Avoid overwatering especially during times of high humidity.
Deficiencies and Disorders
A plant that does not receive its basic needs — water, sunlight, soil nutrients — becomes stressed. A stressed plant is much more susceptible to pest problems and diseases. Most stresses occur over a period of time. While a temporary lack of rainfall or freezing temperatures can certainly damage the plant, these occurrences do not necessarily cause disease. Routine over-watering, poor soil and improper climate conditions invite disease and pests. Peas prefer well-drained soil, a cool growing season and nitrogen fertilizer in soils with low nitrogen content. They benefit greatly from drip irrigation as excessive surface watering encourage rot and the possibility of fungal disease. Therefore, while environment is not a direct disorder, environment greatly influences the common problems that strike pea plants.
The pea has few parasites that affect production but a stressed plant may be plagued by pests that spread more serious diseases. Aphids feed on the sweet sap and transmit Pea mosaic virus and the virus that causes pea stunt. These diseases are characterized by sudden malformations and blisters that appear on the leaves and pea pods. The Pea leaf weevil, native to Europe, chews on leaves and nodules leaving behind a characteristic scalloped edge. Avoid planting peas near clover plants, a favorite aphid food that encourages the pests to further spread to the peas. Spray plants with insecticidal soaps or foliar insecticides. Purchase virus-resistant pea cultivars.
I hope this helps you with your pea plants. If you liked this post, please share on Facebook, Twitter, or StumbleUpon! Thanks for reading.
Photo courtesy of en.wikipedia.org/wiki/File:Doperwt_rijserwt_peulen_Pisum_sativum.jpg.