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College of Food, Agricultural, and Environmental Sciences


Soggy Fields May Promote Wheat Diseases

May 22, 2002

WOOSTER, Ohio - Excessive wet weather throughout Ohio the past several weeks may cause problems with disease development in the state's wheat crop.

Pat Lipps, an Ohio State University Extension plant pathologist with the Ohio Agricultural Research and Development Center, said that growers should be scouting their fields for such diseases as powdery mildew, Stagonospora leaf blotch and head scab.

"Stagonospora leaf blotch is being favored by frequent rain showers. We are not seeing too much of it yet because its been a bit too cool, but we are setting the stage for some major problems with continued rain," said Lipps. "The other disease is head scab and the rains have provided saturated conditions for this fungus to produce spores on old corn residue. Whenever there are high levels of the fungus in the field, there is always the possibility of having head scab in the wheat if it's in close proximity to the corn residue." Lipps said powdery mildew, which was noticed earlier in the season, is beginning to advance in some fields and a return to warmer weather will favor its continued spread.

"Scouting is probably the first thing growers should do right now. Over the next week, we'll probably start seeing some Stagonospora develop on the upper leaves of the plant," said Lipps. "About two weeks after heading, growers should check their fields again because that's when head scab will probably be seen." Wheat growth has been variable throughout the state. The crop in southern counties is in full bloom. Throughout central Ohio, wheat heads are beginning to emerge and in northern Ohio, the crop is currently at the boot stage with head emergence likely to begin at any time. The crop throughout the extreme northwest corner of the state is the least developed, ranging anywhere from flag leaf emergence to the boot stage.

"The crop normally goes into head in Ohio right before Memorial Day weekend. This year we are a little bit ahead of that schedule," said Lipps. "What we'd like to see is the wheat head out as soon as possible and then have a cool period through the flowering and grain filling time. This would provide us with extra days of grain filling which we can take advantage of and is essential to adding more bushels to the yield." In addition to disease development, Lipps said saturated soils have produced some nitrogen deficiency in the crop. "We are starting to see some yellow areas in the fields," he said. "Wheat rapidly takes up nitrogen between jointing and head emergence and this is the period when we were getting all the rain." Unseasonably cool temperatures are also hitting the wheat crop. Those plants with newly emerged heads are most vulnerable to freezing injury when temperatures drop below 30 degrees Fahrenheit.

Lipps said signs of freezing injury - damaged florets and shriveled tissue - can be seen several days after damage has occurred. "Yield loss will be minimal if only the top florets of the head are injured. Otherwise, if entire heads are affected, the loss may be proportional to the number of heads killed," he said.

Lipps added that a forecasted rise in temperatures should rapidly advance wheat growth throughout the state.

Candace Pollock
Pat Lipps