Winter wheat threats

Ray Mueller
Now Media Group


The accuracy of the forecast, based on the crop condition as of May 1, that Wisconsin's winter wheat harvest in the coming months would be as much as 32 percent higher than in 2015 is in jeopardy – for two reasons.

The first setback occurred during the two freezing nights during mid-May in most of the primary winter wheat growing areas of the state. In the wake of temperatures that dropped to 28 degrees or lower for at least two hours at some locations, plant damage and yield losses are likely, according to Extension Service wheat and small grains specialist Shawn Conley.

Based on the growth stage of winter wheat in mid-May this, most of the freeze damage occurred in Wisconsin's southern tiers of counties, Conley indicated. He cited injury to both to the stems and to the then recently emerged heads or spikelets.

If there was stem damage, that wheat would be prone to lodging, Conley indicated. In any such cases, he recommended harvesting the crop for forage.

Stripe rust outbreaks

During the weeks that followed, reports accumulated about severe outbreaks of stripe rust on winter wheat throughout the Upper Midwest, at the Arlington winter wheat trial plot, and in commercial fields in south central Wisconsin.

Monitoring those outbreaks is Extension Service field crops plant pathologist Damon Smith. He pointed out that the winter wheat varieties known to be susceptible to stripe rust had the most severe outbreaks of the disease.

Rainy weather and high humidity, which continued after the initial outbreak of the stripe rust, accommodate the development of leaf diseases, which also include septoria leaf spot and powdery mildew, Smith pointed out. He and several colleagues from the Upper Midwest issued an advisory on how to scout for the diseases and a timetable for applying a fungicide if needed.

With stripe rust, the recommended practice is to scout the lower canopy of wheat plants and then to track if the rust reaches as far up as the flag leaf, which is the most essential component for wheat yields, Smith indicates.

That stripe rust is even more widespread in Wisconsin was the more recent finding of 'severe stripe rust pressure' on the susceptible varieties in the Extension Service's variety trial plot on the Kolbe Seed Farms at Chilton in Calumet County.

'Spray 'em if you've got 'em' was Conley's advice to winter wheat growers. He was referring to the susceptible varieties which growers can identify by checking the annual trial reports that are available online or from county Extension Service agriculture or crop agents. Conley can be reached through the coolbean:info website.

A remaining concern with the 2016 winter wheat crop is the possibility of the outbreak of fusarium blight (head scab) – also a candidate for a timely fungicide treatment – once the heads emerge as they now have in most of the fields in the state.

As of May 1, the prediction for Wisconsin's winter wheat crop was the harvest of a potential 270,000 acres with an average yield of 76 bushels per acre for a total yield of 20.5 million bushels.