Spring 1995
Odds Favor Break in Scab Cycle
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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.
In fact, last year marked the 75th anniversary for one of the area's earliest major scab outbreaks, according to Roger Jones, University of Minnesota extension plant pathologist.
He explains that in 1915 a new wheat variety- Marquis- was released, and it became widely planted because of its resistance to stem rust.
However, 1919 was a very wet year. Marquis was highly susceptible to scab and that year's wheat crop was devastated. The outbreak also infected barley and it lasted about three years.
Jones doesn't know exactly what caused the outbreak to abate, but he suspects Marquis was abandoned and the weather changed.
There were also scab outbreaks in 1983 and 1986. And in the late 1970s, Steve Ross, Ross Seed Company, Fisher, MN, says his company shipped many loads of northern-grown Era wheat to central Minnesota, as wheat there was scabby and not usable for seed.
"In contrast, this year we imported Sharp wheat from that same region, because it was dry there last July and they did not have a scab problem," says Ross.
If history holds true, the odds favor a change in the weather pattern and less chance for scab problems this coming growing season.
That doesn't mean growers should let their guard down on doing what they can to control the disease, however.
Continue to follow the strategies below that help reduce disease risks, offered by Roger Jones and Marcia McMullen, University of Minnesota and NDSU extension plant pathologists, respectively:
* Plant as soon as a satisfactory seedbed can be prepared so grain flowering occurs before mid July, when crop vulnerability to disease pressure and high temperatures are greatest.
* Stagger planting dates so grain flowering doesn't occur at the same time, especially if planting one variety.
* Grow at least three different varieties with different heading times and genetic backgrounds as insurance against different problems.
* Consider tillage during seedbed preparation, which buries disease-carrying debris and lowers the chance of dispersing plant disease organisms.
* Test seed quality and germination, especially if using saved seed from 1992-94. A 56-pound test weight and 85-percent germination should be minimum standards for saved seed.
* Clean disease-infected grain before using for seed.
* Use seed treatments, especially if saved seed tests under 90 percent germination.
* Consider increasing the seeding rate by 10 percent if using seed from 1992-94, particularly if saved seed hasn't been cleaned and has potential for quality and germination problems.
* Plant small grains on last year's broadleaf ground. There's a greater scab risk planting wheat on wheat, corn, or barley ground.
* It might be prudent to budget for a foliar fungicide application at wheat heading (about $10 per acre), at least for acres planted to scab susceptible varieties.
If scab conditions fail to develop, you don't need to make the application. But if leaf diseases begin to get the upper hand, you may still be able to take some action to protect your yields. Contact your local county extension educator or a dealer for details on your foliar fungicide options.