Three species of the Ascochyta fungus can cause this disease:
- Ascochyta pisi
- Ascochyta pinodella, also known as Mycosphaerella pinodella
- Ascochyta pinodes, also known as Mycosphaerella pinodes
According to seed testing procedures approved by Canadian Food Inspection Agency, no distinction needs be made between A. pinodella and A. pinodes.
Why Does it Matter?
- Mycosphaerella blight, which is one of the ascochyta diseases, is found in all pea growing regions.
- Ascochyta pinodes can attack field beans and faba beans, as well as peas.
- Yield loss. Average yield loss in an infected pea crop is about 10% but can be as high as 50% when conditions favour the disease.
What Are the Symptoms?
- Symptoms include lesions on all plant parts, seedling blight and foot rot.
- Lesions start as small dark flecks on the lower parts of the plant and enlarge under humid conditions, often creating a target effect with alternating rings of gray and brown.
- Close inspection of these lesions may reveal small dark fruiting bodies.
- Infection may also be present in the form of foot rot, a blackening of the stem and upper root where the seed is attached.
- Infected seed can be shriveled or discolored or, conversely, may be completely free of symptoms.
What is the Disease Cycle?
- Infection originates from diseased seed or from spores growing on debris in the soil near pea plants.
- Lesions expand rapidly under humid, warm conditions (15o C to 25o C).
- Fruiting bodies are produced in the lesions after about 13 days and spores are spread by rain splash and wind to adjacent plants and fields.
- Pod infection of 10% to 15% will likely produce seed that is 5% to 10% infected.
How is it Controlled?
- Planting clean, disease-free seed is the safest method of control.
- Seed treatments should be used.
- Planting semi-leafless varieties promotes better ventilation in the crop and may help to reduce infection by lowering humidity.
- A 4 to 5 year crop rotation should be followed, and peas should not be planted near fields that have been infected during the previous season.
- Foliar applications of registered fungicides can be helpful if treatment is applied before infection occurs.
How Does 20/20 Seed Labs Inc. Test for Ascochyta in Peas?
- 200 seeds are surface sterilized to remove contaminants on the seed coat then placed on culture agar and incubated for 7 days.
- A qualified staff member examines the plates for the presence of Ascochyta species. Colonies of these fungi are recognizable by the type and color of the mycelium and the spore-bearing structures produced.
- This test gives the percentage of infected seeds to 0.5%. If a lower percentage is required, this can be accomplished by plating more seed. (400 seeds plated will indicate the presence of disease as low as 0.25%.)
- This test takes one week to complete.
Combined tests for botrytis, ascochyta, anthracnose and sclerotinia are available at reduced rates, depending on the number of disease tests requested.
Please contact us for more information.