Grain inspectors in fusarium-plagued Manitoba are finding that there is more vomitoxin in the winter wheat this year than meets the eye.
Until survey results for spring wheat are analyzed, the jury is still out as to the extent of infection in that crop, said Randy Clear, a mycologist with the Canadian Grain Commission.
FDK, which stands for fusarium-damaged kernels, is a commonly used yardstick for quickly measuring the amount of vomitoxin, or DON, in a sample of wheat.
It has been one of the primary downgrading factors in Manitoba winter and spring wheat this year.
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Extremely high levels in the Interlake were recorded this year because of a very wet growing season, and parts of the northwest were also hit.
Fusarium is making its way into eastern Saskatchewan, Clear said.
Normally, two to three parts per million of DON was common for every one percent of FDK in a sample, but now tests are showing more variability.
The greater degree of unpredictability may lead to headaches for grain marketers.
“We bin grain, we blend grain and we grade grain based on the percent of FDK,” said Clear.
“So if you tell a customer that it will be around one ppm DON, and you find out later that it’s two, then you have a problem on your hands.”
Although many winter wheat varieties have less genetic resistance to fusarium, farmers in areas where residual inoculum levels are high may choose to plant it instead of spring wheat.
Winter wheat’s early maturity may see it pass through the susceptible flowering stage before hot, humid weather arrives in early summer.
That strategy may have to be revisited, he added.
“Last year was one of those odd years when the winter wheat was badly affected, but the spring wheat flowered when it was dry and the spring wheat had almost nothing in them,” he said.
“Usually it’s been the other way around. The winter wheats are all about escape, and not getting infected.”
Mike Grenier, an agronomist with the Canadian Wheat Board, said the extent of the problem was not apparent leading up to harvest.
“We saw in the field surveys in August that the presence in the field didn’t look too bad. Then at harvest time, the grain samples started coming in did show that the disease was there, but even they didn’t look too bad,” he said.
“But once we started running DON analysis on the samples, it became apparent that there were areas where the DON levels were elevated, and more so than what would normally have been expected given the number of fusarium-damaged kernels in the sample.”
The worst DON levels were as high as five ppm, effectively ruling out the grain’s usefulness for the CWB’s milling and baking customers, who can’t tolerate DON higher than one ppm.
Elevated levels were seen in red spring wheat as well as malting barley, but the winter wheat appears to have been hardest hit.
Dean Stoyanowski, an Arborg-based adviser with Manitoba Agriculture, said the variability in wheat DON levels, especially in the drenched Interlake, means that testing of wheat used in livestock rations is more important.
