June 26, 2003

 

Producers Need to Monitor Wheat and Barley Fields for Leaf and Head Diseases

The risk of infection by fungal pathogens such as fusarium head blight is increasing because of recent moderate to heavy rains across North Dakota, according to Marcia McMullen, North Dakota State University Extension plant pathologist. "Keeping ahead of disease development can be difficult at this stage of the growing season."

McMullen suggests frequent field scouting, checking accumulated growing degree-days through the North Dakota agriculture weather network and using the decision tools available on the small grain disease forecasting Web site. "Growers and crop advisors should look at crop growth stage, yield potential and disease risk when making a decision on the appropriate fungicide," she says.

Barley needs to be sprayed for leaf and head diseases by early full head emergence. "If fusarium head blight is the target, then barley should be sprayed at early head emergence after the heads are out of the boot," McMullen says. "Spraying barley heads while they are still protected by the leaf sheath will not provide coverage on the critical infection site, the grain head."

Wheat leaf rust is now common and in some cases severe in south central and southeast counties. "Wheat leaf rust is an explosive disease and growers must keep on top of it," McMullen says. "Wheat fields can be sprayed with fungicides for effective leaf rust control if two conditions are met:

• The crop has not reached post flowering stage.
• The flag leaf still has zero to less than five percent infection.

If these conditions are not met, then it is generally too late to spray.

Wheat needs to be sprayed at early anthesis or flowering for scab control. This is generally when 10 to 25 percent of the main stems have started to flower, not when 10 to 25 percent of the crop has headed. Like barley, protection for wheat can only be achieved when the fungicides are applied to the exposed grain head. Research shows that optimum results are obtained when fungicides are applied during flowering.

Folicur fungicide has a 30-day pre-harvest interval for wheat and barley, while Tilt has a 40-day pre-harvest interval for wheat.

The North Dakota agriculture weather network can be accessed at http://ndawn.ndsu.nodak.edu  while the small grain disease forecasting Web site is http://www.ag.ndsu.nodak.edu/cropdisease/ .

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Source: Marcia McMullen, (701) 231-7627, mmcmulle@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu