Researchers at Montana State University report an increasing number of samples of pulse crops containing significant amounts of the fungus blight Ascochyta in the past year.
The findings represent an increase compared to 2010 samples, particularly in lentils. With pulse crops going into the ground soon, there is confusion about the acceptable level of the disease in a given crop.
Ascochyta is a potentially serious fungul disease in pulse crops, including lentils, peas and chickpeas. The disease can defoliate plants and spread rapidly. One way to prevent the disorder is to plant fungus-free seed. Growers can test seed lots for the disease by sending them to the MSU lab.
The test requires 10 days after the seed is planted by technicians at the university, as the fungus needs to grow out of the seeds before it can be identified. Producers should be sending seed to the lab now to provide enough time to receive results and make management decisions before planting.
While there are not definitive acceptable levels of the fungus, these guidelines provided by MSU may help:
There is a zero percent tolerance for chickpea which is highly susceptible.
Pea and lentil are more resistant, so MSU Plant Pathologist Mary Burrows recommends less than 2-5% disease in the seed for these crops.
There are no definitive thresholds for disease development: a higher number may indicate a greater risk for disease development, but that does not guarantee the disease will manifest in planted crops.
A low /zero number in the test does not mean the disease will not occur. The disorder requires a susceptible crop, the pathogen and a conducive environment.
If the blight level is above the threshold, Burrows recommends using LSP/Mertect fungicide at planting. This is the only seed treatment fungicide with good efficacy against Ascochyta blight according to MSU field trials.
It is applied in addition to seed treatment to control damping off and root rots.