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.”

Pulse Crop Questions?

Jesse Fulbright, MSU Liberty County Extension Agent

2016 may have been the international year of pulse crops but around here it seems that 2017 is the big year for pulses.  There have been several workshops around the area over the past several months, both Extension related and private industry.  I wanted to share with everyone an e-mail I sent out to producers last week that covers some questions I have been receiving.

First, is there a need for a seed treatment?  The answer would be a resounding YES.  Please do this to help prevent diseases now and in the future, if nothing else for our market in the Golden Triangle.  Seed treatments are recommended on all pulse crops to protect against both seed borne and soil borne fungi.  Pulse crops are susceptible to many soil-borne fungi including Pythium, Fusarium, Rhizoctonia, and Aphanomyces.  Seed borne fungi, such as Ascochyta, Botrytis, Sclerotinia are also a risk.  Producers should always use a seed treatment as a best management practice to avoid pathogen buildup in the soil.  Use products with mixed modes of action to target the different types of fungi that are present in seed and soil.  It is important to rotate fungicide classes, or modes of action to avoid the development of fungicide resistance.  This includes seed treatment applications as well as foliar applications. 

Regarding ascochyta blight, how is it spread?  Ascochyta blight is the most problematic foliar disease of pulse crops. The causal agent is host specific, Ascochyta pisi causes blight on peas; Ascochyta rabiei affects Chickpea and Ascochyta lentis attacks lentil.  The pathogen can overwinter in fields on crop residue for several years and in the spring the sexual spores produced from the stubble can be dispersed by the wind for up to 5 miles.

When talking about fungicides, what is the difference between those fungicides ending with -strobins and -zoles?  Strobins tend to be used for more preventative measures while -zoles are more curative, or after a problem occurs, although there is a small window of preventative as well.

Can a producer get away with applying at less than the recommended rates of any pesticide?  Yes, you could, but are you really willing to wager that?  Please apply at the recommended rates.

Do seed cleaners clean the diseases off?  No, that’s another important reason to use seed treatments. 

Lastly, are there recommendations for soil temperatures at which to plant pulses?  Yes, 40°F is the recommendation for peas and lentils while it is 45° for Desi chickpeas and 50° for Kabuli chickpeas.