Tuesday, April 18, 2017

Ascochyta Blight

Jesse Fulbright, MSU Liberty County Extension Agent

Whether you are in the field yet or not, if you are planting pulses this spring, I have some information to share with you about pulse diseases, specifically, Ascochyta blight.
Ascochyta blight is a foliar fungal disease in pulse crops, with strains being host specific.  For example, the strain that affects peas will not affect lentils or chickpeas.  Lesions from Ascochyta in chickpeas are circular or oblong and may begin as small, light-colored specks on the leaf which expand into target-shaped lesions.  Under moist conditions, each wave of the lesion is surrounded by a brown or black halo.  These can occur on stems, petioles and pods in chickpeas.  Lesions on peas tend to be more restricted and the target pattern less obvious.  Lesions on lentils are a lighter brown with a dark brown halo, but also often lack the target pattern.  Lesions on plant tissue can cause defoliation, stem breakage and lodging. 

Management of Ascochyta blight begins at planting.  This is a residue-borne disease, hence one of the reasons for the recommendation from Extension and insurance companies that you wait 3-4 years between the same legume crop.  The pathogen can be seed-borne at high levels.  M.S.U. Extension recommends 0% seed-borne infection for Ascochyta in chickpeas and below 5% for peas and lentils. 
Ascochyta can also blow in as spores from other pulse growing areas.  Environmental conditions favoring disease development include cool temperatures between 59 to 77° F and high humidity.  The decision to spray foliar fungicide will depend on the crop and variety, the timing of the infection, the percent of plants infected and the severity of the infection.  Many foliar fungicides are effective against Ascochyta blight.  Fungicides should be applied at bloom initiation or canopy closure, or when the first symptoms are seen.  Additional applications may be necessary, but please pay attention to label restrictions and rotate fungicides to prevent the development of resistance to certain chemical classes.

For further inquiries about Ascochyta blight or other pulse diseases, contact your local county Extension office for a copy of the publication titled, “Diseases of Cool Season Legumes.”

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