CROOKSTON, Minn. — The “old nemesis” — scab — is back to bedevil spring wheat farmers in northwest Minnesota.

Jochum Wiersma, a University of Minnesota Extension cereals crops specialist, offered a research plot tour on July 21, 2020, as part of the Agweek Cereal Crops Tour.

Farmers are dealing with the after-effects of a chain of excessive rains from mid-June through late July. “Right now I’m worried for the area from Crookston, north,” he said.

Rains have led to scab (fusarium head blight) and other problems for northwest Minnesota wheat yields and quality. It wasn’t hard for Wiersma to find scab in the plots untreated with fungicide. He ruefully noted the “beautiful” salmon-pink confirms the scab diagnosis.

It isn’t hard to find wheat scab disease (fusarium head blight) on July 21, 2020, in untreated research plots, says Jochum Wiersma, University of Minnesota Extension Service cereal grains specialist at Crookston, Minn., Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
It isn’t hard to find wheat scab disease (fusarium head blight) on July 21, 2020, in untreated research plots, says Jochum Wiersma, University of Minnesota Extension Service cereal grains specialist at Crookston, Minn., Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
Many wheat fields received what Wiersma calls a “priming rain” about seven to 10 days prior to heading. This starts the inoculum production, and those areas likely will be worse for scab compared to the central and southern Red River Valley.

“The story is going to be — again — that we’ll have to start paying attention to how we’re going to harvest this crop,” Wiersma said. “We’re going to have to see how much damage there is with scab, whether we have to start separating fields based on the amount of scab, (and) be careful with how we harvest.”

If a farmer sets a combine correctly, many of the early-infected scabby kernels (aptly described as “tombstone” kernels) will blow over the back of the combine.

Bacterial leaf streak is another disease hitting northwest Minnesota wheat crops in 2020, apart from the fusarium head blight, or scab. Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
Bacterial leaf streak is another disease hitting northwest Minnesota wheat crops in 2020, apart from the fusarium head blight, or scab. Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
Apart from scab, other diseases such as “tan spot” and “bacterial leaf streak” are starting to show up.

Beyond the diseases, farmers are dealing with simple drown-outs. When water stands for two days and temperatures are over 90, that stresses or kills plants. The week of June 20, it was a lot cooler, which slowed the “race to maturity,” to maintain yield potential.

Straight-line winds have not been good, but lodging is better than 2019. The crop overall was shorter to begin with, due to dry conditions earlier in the season. It’s a “three strikes and you’re out” situation because of the number of “nodes” that come back up.

“Two times it can do that, the third time it is very tough to come back up,” Wiersma said.

The “old nemesis” -- scab disease -- is hitting northwest Minnesota  wheat crops, suffering from excessive rains since mid-June 2020. Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
The “old nemesis” -- scab disease -- is hitting northwest Minnesota wheat crops, suffering from excessive rains since mid-June 2020. Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
Linkert is a popular wheat variety in part because of its outstanding straw strength.

An annual Wheat Quality Council spring wheat tour, which was cancelled for 2020, uses three components — number of tillers per unit area, spikelets per spike, and kernel set — to estimate yield.

“On ‘skinny’ (yield) years, where the crop is really stressed, you will only find a kernel on the side of each spikelet, so there’s two. On good years, you’ll start seeing three and four kernels per spikelet.”

Estimating yield is difficult in the very best of years, but “almost impossible” when the crop is variable with drown-outs.

The “old nemesis” -- scab disease -- is hitting northwest Minnesota  wheat crops, suffering from excessive rains since mid-June 2020. Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
The “old nemesis” -- scab disease -- is hitting northwest Minnesota wheat crops, suffering from excessive rains since mid-June 2020. Photo taken near Crookston, Minn., July 21, 2020. Mikkel Pates / Agweek
"The best fungicides, with the best genetics give us the best chance to deliver a crop that the market wants,” Wiersma said.

With prices down, farmers must decide whether to make a $15 per acre investment into a crop that is uncertain because drown-out.

“There are some cases where I’ve told growers to walk away from fields. It just doesn’t pencil right now," he said.