Pulse Crop Ascochyta

The disease known as Ascochyta blight can be a serious problem in pulse crops such as chickpea, lentil, and field pea. Ascochyta blight is seed transmitted and can be spread by infected plant residue blown into a field. Ascochyta blight is crop specific, meaning that lentil Ascochyta blight will only infect lentil and not chickpea, field pea, or other pulse crops. The same is true for chickpea and field pea Ascochyta blight. There are similarities in the symptoms of Ascochyta blight on pulse crops, but controlling this disease varies among crop types.

Lentil Ascochyta
Symptoms of Ascochyta on lentils can occur on leaves, pods, and stems as white to tan spots with a darker outside margin. The centers of these lesions can be speckled with the black fruiting bodies which contain spores of the fungus. Infected seed can be discolored with a brownish color. Moist weather is conducive to the development and spread of the disease. Infection levels of 1% or greater are considered high. Ascochyta can cause yield losses of 30-50% in susceptible varieties.

Control
Effective control measures include:

• crop rotation
• application of fungicides
• resistant varieties 

Chickpea Aschochyta
This disease can be devastating in chickpea as it can spread very quickly and can cause significant yield losses. All above ground portions of chickpea plants can be susceptible. Relatively low seed infection levels can cause serious problems in the field. In fact, seed infection levels greater than 0.3% or higher would be considered high. In cases such as this, it would be best to look for new seed. Symptoms on chickpea include the development of dark, sunken lesions which contain rings on the outer margin. Spores are often present in these lesions. Cool, moist weather conditions favor development of this disease. However, spore production can occur under relatively dry conditions providing inoculum for rain splash secondary infections.

Control
The best control measures for chickpea are:

• planting disease-free seed
• resistant varieties
• crop rotation

Field Pea Ascochyta
Field pea can be infected by more than one species of the fungus. All above ground portions of pea plants can be susceptible to this disease.  Symptoms on peas include the development of purplish black to brown spots or lesions on stems, leaves, and pods.  Black spore producing structures may form on these lesions.  Pod lesions may become sunken.  The fungus can over-winter in seed, infected crop residue, and in the soil.  Seed infection levels of 5% or greater would be considered high.

Control
The best control measures are:

• crop rotation
• planting disease-free seed

Testing
The Seed Department currently conducts seed tests for Ascochyta in lentil, field pea, and chickpea. The Ascochyta test is required for labeling of chickpea and lentil seed, and the test results must be on the label. Results of this test are reported as percent infected seed of 500 seed tested. This test is typically completed in 8-10 days and requires varying amounts of seed depending upon the crop. Small seeded types such as lentil require a minimum of ½ lb. of seed while larger seeded types such as chickpea or field pea require a minimum of 1 lb. of seed. Chickpea samples can also be tested for Ascochyta using 1,000 seed if required.