- A species of the Ascochyta fungus called Ascochyta rabiei causes this disease.
Why Does it Matter?
- Ascochyta blight is the most economically significant disease of chickpeas.
- The disease can spread rapidly, wiping out a field in as little as a single day if conditions are right.
- Yield loss. Depending on weather conditions, yield losses can be up to 70%, even with resistant varieties, and complete yield loss is possible.
- Grade loss. Pod infection can result in 50% to 80% infected seed, which is likely to be shriveled and discolored, substantially reducing grade and germination rate.
What are the Symptoms?
- Small reddish-brown spots appear on leaves and stems.
- The lesions turn brown with a dark margin and develop a yellowed center as they increase in size.
- If lesions girdle the stems, upper plant parts will wilt, die and can break off.
- Close inspection of lesions may reveal small dark fruiting bodies.
- Pod lesions are circular with dark margins and rings of fruiting bodies
- Infected seed may be shriveled, spotted lesions of various shapes and sizes and/or darkly discolored.
What is the Disease Cycle?
- Ascochyta rabiei is carried on infected seed and crop residue.
- Disease occurrence in the crop is usually the result of planting diseased seed.
- Spores on crop residue can live for a couple of years at most in the soil, however, the type of spore produced in this debris is capable of spreading infection by wind to nearby fields, even to fields several miles distant.
- The disease grows best under humid conditions at temperatures from 20o C to 25o C.
- Physical symptoms are evident as little as 4 days after infection. Spores are produced shortly after these symptoms appear and can be splashed by rain or blown by wind to adjacent plants.
- This rapid cycle means several generations of spores can be produced during one season.
How is it Controlled?
- Plant disease-free seed only.
- Use a seed treatment to encourage healthy vigorous seedlings.
- Follow a 3 to 4 year crop rotation and avoid seeding chickpeas near previously infected fields.
- Because symptoms become visible after infection has occurred, use a preventative fungicide program. Begin spraying when disease pressure is low.
- If disease pressure is high, a foliar application of a registered fungicide at early podding can help protect the seeds from infection.
- Chickpea varieties with pinnate leaves promote better ventilation in the crop and therefore usually have lower infection rates than varieties with uni-foliate leaves.
How Does 20/20 Seed Labs Inc. Test for Ascochyta in Chickpeas?
- 400 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 rabiei. Colonies of this fungus 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 0.25%.
- 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.