Ergot and its effect on your wheat grade

What is ergot?

Ergot is a plant disease which is caused by the fungus Claviceps purpurea in wheat. In an infected plant, kernels are replaced by ergot bodies or sclerotia. These are black or dark purple and hard. Because they grow in place of a wheat kernel, these bodies can be almost the same size and shape as a wheat kernel. You may also see ergot bodies that are much larger than wheat kernels.

Figure 1, left to right: Ergot-infected wheat head, ergot-free wheat, ergot bodies.

Figure 1. A comparison of wheat kernels to ergot bodies (centre and right).

As seen on the wheat head (left) in figure 1, an ergot body replaces the affected kernel as it grows, resulting in an ergot body that is similar in size and shape to the kernel it replaced.

What causes ergot?

One of the main contributing factors to the incidence of ergot is weather. If the weather is cool, cloudy and wet when cereals, such as wheat, are flowering, ergot spores may enter the floret and begin developing into ergot bodies. At harvest, ergot bodies can fall and lodge in the soil. These can survive over the winter and, if the soil is wet enough in the spring, they can release spores that may infect new crop and weeds.

How does ergot lower my grade?

Ergot is a grading factor in Canadian wheat. For the exact tolerances for wheat, refer to the Official Grain Grading Guide.

A sample of wheat that is within tolerance for every other grading factor may be degraded as low as Canada Western Feed or No. 5 Canada Western Amber Durum or less for what seems to be a small amount of ergot. However, the tolerances for ergot are tight for safety and quality reasons. To receive a specific grade, a sample of wheat must be within tolerance for every grading factor.

Ergot is toxic to both humans and animals, even in small amounts. As well, this toxicity cannot be reduced through processing. Any flour or feed made from ergot-infected wheat will still be toxic. The impact of ergot on end-use quality is of minor concern when compared with ergot’s toxicity.

How are grading tolerances for ergot set?

Grading tolerances for ergot are set based on the results of scientific research conducted by the Canadian Grain Commission and based on recommendations made to the Canadian Grain Commission by the Western Standards Committee and Eastern Standards Committee. Both committees’ members represent all parts of the grain industry, including grain producers. At their twice yearly meetings, the committees consider the results of our scientific research and input from various stakeholders across the industry. Each committee reviews current grain grade standards to ensure they continue to be relevant for everyone involved in Canada’s grain industry including producers.

What can I do about ergot in my wheat?

Before you deliver, we encourage you to find out your grade and if ergot is a grading factor in your crop. You can sign up for the Harvest Sample Program to submit a sample and receive a free grade, including grading factors. Or, for a fee, you can send a representative sample of your crop to any one of our service centres, where one of our inspectors will grade your grain as part of our Submitted Sample Service.

Once you know if ergot is an issue in your wheat, you can begin researching your options for seed cleaning, including types of service and any fees charged. By having all the information before you deliver, you can make choices that work for you.

Ergot is difficult to clean from wheat because the most common cleaning equipment separates foreign material, like ergot, by size and shape. While some ergot bodies are larger than wheat kernels, most are similar in size and shape.

Many seed cleaning companies and some licensed primary elevators have the capability of removing ergot through use of specialized equipment. The most common means of removing ergot is through use of a gravity table, using differences in density to remove ergot bodies from wheat. Some seed cleaning companies and licensed primary elevators may use a colour sorter, a newer technology. A colour sorter is a computerized piece of equipment that removes any material that differs in colour from wheat.

What can I do to prevent ergot?

There are several strategies related to agronomic practices that you can follow, including during harvesting, tillage and seeding (Pearse, 2006).

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Definitions

Grade of grain
A grade of grain is defined by the specifications in the Canada Grain Regulations and by the additional specifications found in the CGC's Official Grain Grading Guide.
Grading factor
A grading factor is a physical condition of grain, the result of growing conditions, handling procedures or storage practices. It is a visual characteristic that indicates a reduction in quality; for example, frost damage, sprouted kernels, or heated kernels.
Sample
A sample is a portion of grain taken to represent an entire truckload, carload or cargo.
Submitted sample
A submitted sample is an unofficial sample sent in by a grain company or producer for grading or for other tests. The Canadian Grain Commission charges a fee for any analysis on a submitted sample.

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