For many farmers who struggled with excess moisture to get their crops in and off last year, the biggest hurdle of the 2010 crop year may still be in front of them — trying to market grain with high levels of ergot.
Ergot is a fungal parasite which infects grasses and cereal grains. Unlike other fungal diseases, ergot does not significantly impact yields. The problem is the ergot bodies, which form in the place of seeds, contain alkaloids. These are toxic to both animals and humans. Consumption of ergot can lead to lameness, abortions, convulsions, gangrene and even death in animals. There are also risks to humans. The medieval disease St. Anthony’s fire was likely a result of people consuming flour milled from ergot infested grains. The hallucinogenic side effects of ergot poisoning (ergotism) is thought to have contributed the Salem Witch Trials.
Due to this toxicity, the presence of ergot cannot exceed 0.01 per cent by net weight in No. 1 wheat and livestock feed must not contain more than 0.10 per cent ergot. These levels will be difficult for many growers to achieve given the level of ergot infestation last year.
Unlike most years, where there are small pockets of ergot here and there on the Prairies, infection was widespread last year, according to Norm Woodbeck, program manager for standards and re-inspection with the Canadian Grain Commission.
To illustrate the extent of the problem, Woodbeck says, “In the 2010 harvest survey we found seven per cent of wheat samples were downgraded from a No. 1 to No. 2 due to ergot, 20 per cent were down graded to a No. 3, and 35 per cent of (last) year’s wheat crop grades feed because of the amount of ergot in the sample.”
While removal of the ergot may improve the grade, there may be other factors that also contributed to the downgrading, he notes. Woodbeck suggests farmers find out not only the grade of the wheat in the bin, but also the grade after cleaning to determine if ergot is the only factor that caused the downgrading. If its removal will result in a higher grade, it may well be worth spending the money to have it cleaned.
According to Woodbeck, last summer’s weather conditions are to blame for the high levels of ergot. Ergot bodies require soil surface moisture in the spring to germinate. The fungal growth from the ergot body produces spores which become airborne. These spores land on the florets of flowering grasses and cereals, and replace the developing seed embryo with a new ergot body. Cool, wet and cloudy weather during flowering of the crop extends the time of flowering and thereby increases the amount of time the plant is susceptible to infection.
There are also a number of agronomic factors linked to ergot infection. Poor fertility can delay maturity or cause uneven maturity which increases the flowering period and results in more infection. Copper deficiency delays flowering and can
Rye No. 2
Special Select Nil
Standard Select No limit
cause male sterility in the plant, which results in florets remaining open longer and increasing the chances of infection.
Some farmers believe new high-yielding wheat varieties are flowering twice and that is the reason ergot is bigger problem, but Agriculture Canada wheat breeder Ron DePauw disputes this.
“The flowering process of new varieties of wheat is similar to that of wheat grown for the last 100 years,” he says.
Instead, DePauw says farmers were likely seeing late-flowering tillers caused by the abnormal growing conditions last year. Because of the weather conditions, many growers observed a second set of tillers which were taller than the primary crop. The flowering of these tillers significantly lengthened the flowering period of the crop as a whole and increased the potential for infection. According to DePauw, under normal growing conditions this second tillering would not have occurred.
Herbicide injury can also lead to increased ergot, says DePauw.
“Some of the new herbicides are a little hotter. The male organ on a plant is very sensitive to herbicide injury and male sterility can result. As a result, the floret of the plant remains open longer looking for pollen, increasing the chances of ergot spores replacing the pollen.”
Removal of ergot from grain is possible. Standard cleaning equipment that separates foreign material on the basis of size will work if the ergot is larger or smaller than the grain kernels. Unfortunately, ergot is often the same size as the grain. Furthermore, ergot bodies can easily break from mechanical handling, resulting in more kernel sized pieces of ergot that cannot be cleaned by size.
Gravity table cleaners, which work on the basis of density, are very effective as ergot is less dense than seeds, however, this process tends to be expensive and slow. As with size cleaning, there can be considerable amount of grain left in the screenings. Due to the higher concentration of ergot in the screening, screenings usually cannot be fed to livestock, adding to the cost of disposal.
Colour sorters can do a very good job of removal of ergot from cereal grains because the purplish black colour of the ergot bodies is so different than the colour of the grain, and that also means reduced screening losses. However, there are relatively few colour sorters available for the amount of grain infected on the Prairies.
Seed growers with small, expensive seed lots also have the option of a water bath. Ergot floats, so immersing the seed in a 20 per cent salt water solution and stirring allows the ergot to float to the surface where it can be skimmed off. The seed must then be dried again, of course, further adding to the cost.
The most important consideration before cleaning is to determine if it is economical to clean the grain. Unless you gain a grade or market, it may not be worth the cost.
The only good news about ergot is the fruiting bodies rarely survive more than one year. Even if ergot was bad in your fields last year, good crop rotation and management practices will minimize the chances of it being a problem in the future. But you need to plant clean seed and rotate between broadleaf and cereal crops, as broadleaf crops are not susceptible to ergot. Avoid planting cereals on fields known to have ergot infected residue, and mow grass in adjacent ditches and water-runs early in July before the grass flowers, says Tom Boyle, regional crops specialist with the Saskatchewan Ministry of Agriculture. Scouting fields for ergot prior to harvest can allow infected areas to be harvested and binned separately to reduce further contamination problems, he says.
Also, use a balanced fertility program, a high seeding rate and seed at a constant depth so the crop matures evenly and flowers quickly. Use the proper rate and timing of herbicides to prevent herbicide injury in the crop. Grassy headlands and ditches are an alternative host for the pest; keep them mowed. If ergot is observed in the field at harvest time, you may want to consider harvesting and storing the production from the perimeter of the field separately as this tends to be where ergot is the worst. Delaying harvesting of standing crop is another option as ergot bodies can fall out of the head, however the risk of downgrading due to weathering will increase.
There may or may not be a varietal difference in ergot susceptibility. Since environmental conditions play such a key role in the occurrence of this disease, it is difficult to know if one variety is more susceptible than another or if it is simply a case of conditions being optimum for ergot infection at the time a particular variety is flowering.
Since there is a difference in when varieties flower, some growers seed more than one crop variety, hoping one variety will flower prior to or after the time when ergot infection is occurring. Other growers try to seed all their cereals at the same time so there is a narrow period of time when flowering is occurring and less chance of infection spreading from field to field.
As far as crops go, triticale and rye tend to be most susceptible of the cereal grains. Of the wheat classes, CPS and amber durum are believed to be slightly less susceptible to ergot infection than the HRS wheats. Oats rarely get ergot.
There are no seed treatments or fungicides which prevent or control ergot.
One final note: Are you sure ergot is your problem? Sclerotina’s over-wintering form, sclerotia bodies, are usually smaller than ergot, but can have a similar appearance. Sclerotinia does not infect cereal crops but if you had a high level of volunteer canola in your cereals due to an inability to spray your crops last year, there is a chance some of what look like ergot bodies could actually be sclerotia bodies. A qualified grader can easily distinguish between ergot and sclerotia bodies.
ALLOWABLE GUIDELINES FOR ERGOT IN GRAIN (COURTESY CGC)
CWRS / CWHWS
CWES / CPSW / CPSR
Malting (2-and 6-row)
No. 3 / No. 4
No. 3 / No. 4
No. 1 No. 2
No. 2 Feed
Ergot (per cent of net weight)
3 K (no. of kernel sized pieces in 500 g)