Wheat Fusarium head scab (also known as head blight) causes tremendous losses by reducing grain yield and quality when above normal moisture and temperatures occur as the wheat crop flowers. Much of the wheat in Butler County was headed by May 14 or 15 and a few fields headed before that.

Flowering occurs a few days after heading is complete. When the head has those funny-looking little things sticking out from the head, you know the pollen has been shed. They are anthers, which contain the pollen. When they are outside the flower, the job is done. When flowering has occurred all the way to the base, the wheat is said to be at Feeks Stage 10.5.3.

Flowering usually occurs in Butler County between the third and fourth week of May, so we are on the early side this year. When weather conditions are favorable during flowering, head scab can cause an epidemic. An epidemic is defined as 10 percent of the heads showing damage. Head scab is caused by the fungus Fusarium graminearum.

Several universities have joined forces over the past several years to develop a reliable predictive system to help wheat producers assess the risk of head scab in their region. Researchers from Ohio State University, Purdue University, Penn State University, North Dakota State University and South Dakota State University have worked together to develop models (www.wheatscab.psu.edu/) that have been very accurate in predicting an epidemic with greater than 10 percent severity.

If your wheat had flowered by May 18, the risk for scab based on moisture and temperature was low. That may change by the time you read this article since it is raining as I write.

Check the website often as conditions change. We have had cool night temperatures, which may help. Scab fungus grows best at temperatures between 55 and 78 degree F.

The risk for wheat that was planted after corn is higher if the crop residue covered at least 10 percent of the soil surface. This is because there are many more spores available in the corn residue to get the disease started than in a field that was in soybeans last year. This is the reason we are recommending wheat be grown after soybeans rather than corn.

You can usually start to see the symptoms of scab two to three weeks after the infection of the head. Hopefully the low risk prediction holds and the scab will not be important this year.

This farm news was published in the May 31, 2006 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.