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Controlling ascochyta in chickpeas

If you’re going to grow chickpeas, you’re going to need the right variety, 
good rotation practices, and, of course, a lot of fungicide

While chickpea production in 2012 was higher than 2011, there’s no doubt that Prairie production has been held back by ascochyta. When left uncontrolled, Ascochyta rabiei has been responsible for yield losses as high as 70 per cent. Although plant breeders are working on new varieties with higher resistance, the disease still needs to be carefully managed.

Ascochyta blight is a crop-specific, seed-borne disease that causes yield losses in chickpeas, lentils, and peas. The pathogen over-winters in crop residue or infected seed, and develops in early spring. It produces two different types of spores: conidia (asexual spores) and ascospores (sexual spores).

Ascospores are airborne and have the ability to infect crops located miles away from the infected residue. Once the plant has been infected, symptoms, including disease lesions on pods, stems and leaflets, will begin to appear within four to six days. These symptoms can lead to devastating problems, including stem breakage and leaf death.

Scouting for ascochyta

In chickpeas, ascochyta appears before the crop, as early as May.

When scouting for ascochyta, the Government of Saskatchewan guide Scouting and Management of Ascochyta Blight in Chickpea recommends scouting in a W-shape or a large circular pattern, inspecting five to 10 sites.

Be sure to check those fields that are either more vulnerable to disease or potential disease hot spots. Hot spots will be areas that are more heavily seeded areas, areas with excessive moisture, and sections that have been damaged by drought, herbicide injury or frost.

Start scouting as soon as the seeds emerge (within two to three weeks of planting). During this critical period, you should scout every three to seven days. If weather conditions — frequent rain showers and humidity — are favourable for ascochyta, increase scouting frequency. Continue scouting until the pod filling stage.

Early symptoms of ascochyta include small lesions the size of a pinhead. They occur on the leaflets and stems, and are light tan to dark brown in colour. The lesions will be embedded in the leaf and cannot be rubbed off.

Managing ashochyta

There are three key parts to an ascochyta management strategy.

1. Fungicides: “Foliar fungicides are a very effective tool to manage ascochyta blight,” say Miller.

Usually, multiple applications are required. Miller says, “Resistance to fungicides may develop as a result of the repeated use of fungicides belonging to the same chemistry family.”

Your best precaution against resistance, Miller says, is to “follow a rotation of products with different active ingredients and tank-mix products from different fungicide groups where registered.”

If conditions are wet, spray a preventative foliar fungicide at the seven to 10 node stage. If it’s dry, you can hold off a bit longer. But make sure that your first application is before flowering; protecting the flowers will conserve yield.

Once the crop reaches the pod filling stage, Although a fungicide application at this point won’t affect yield, it can help to improve seed quality.

2. Variety choice: In recent years, advancements in agronomic research and variety development have greatly reduced the impact of ascochyta blight in chickpeas.

Ideally, choose a variety with no more than 10 per cent ascochyta infection.

3. Crop rotation is key: Since ascochyta blight only survives on the residue of specific crops, your first and most important line of defense in managing for the disease is crop rotation. Most farmers avoid planting chickpeas more than once every four years in the same field.

For more information on ascochyta, Miller recommends the 2013 Saskatchewan Guide to Crop Protection.

Chickpeas in rotation

Ascochyta is an ongoing problem on Shawn Bourgeouis’ farm near Woodrow, Sask., which is why he avoids growing chickpeas more than once every four years, as recommended.

“Chickpeas remain a small part of our overall rotation due to the high production and market risk,” says Bourgeouis. “In the past, Saskatchewan and Alberta farmers have grossly increased production well beyond market demand, making it very difficult to sell the product. Because of this, many farmers have learned to exercise serious caution when including chickpeas in their rotation, in spite of occasionally strong prices.”

“As a general rule, we plan three to five applications of fungicide per year, depending on weather conditions,” he continues. “We try to alternate groups of fungicide with each successive treatment. Risk of ascochyta developing resistance to group 11 fungicides is apparently higher than the other fungicides, so we try to exercise caution with strobilurin dependence in our treatment rotation. This includes products like Vertisan, Quadris, Proline, Priaxor and Bravo.”

For more information on how to manage ascochyta blight, please see the Government of Saskatchewan’s online resource, Scouting and Management of Ascochyta Blight in Chickpea . Find it by searching for “chickpea” at www.agr.gov.sk.ca.

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