Disease Management Is Key To Great Wheat

Disease management with timely fungicide application must be a top priority to grow great wheat crop, Ohio State University pathologists say.

“In 2010, the more aggressive managers had the better wheat,” say Ohio State University pathologists Pierce Paul, Dennis Mills, Katelyn Willyerd and Allissa Kriss wrote in a recent issue of the university’s agronomy newsletter.

“Some folks were just lucky, but in general, those who had resistant varieties planted and applied a fungicide at the right time, saw better yields, test weights, and had lower levels of vomitoxin. Let us start by choosing resistant varieties, especially to head scab, as we plan for our next wheat crop,” the Ohio State University pathologists say.

“We had everything this year — head scab and vomitoxin, Stagonospora leaf and glume blotch, powdery mildew, leaf rust, head smut, cereal leaf beetle, plus a very hot late-spring-early-summer.

"The big problem this year was head scab and vomitoxin, with incidence ranging from 3% to 60% and vomitoxin from less than 1 ppm to 18 ppm. Both Stagonospora and powdery mildew were also very severe, with a severity score of 7 out of 10.

"Diseases combined with a short grain fill period resulted in low to moderate yield and grain quality, with average yield ranging from 40 to 90 bushels acre and test weight from 45 to 60 pounds per bushel.”

On the positive side, it was rare to find all of these diseases in the same fields and some fields escaped most of these problems, the pathologists say.

Fungicide Timing Matters

Fields that escaped or largely escaped disease did so for a number of reasons. They were planted to with resistant varieties or after soybeans. They may have been treated with a fungicide at the right time, flowered before or after the rains or a combination of all of these factors. The good news from a year with many diseases attacking wheat is that timely fungicide application made a huge difference, the pathologists say.

“Even in areas where the scab levels were high, some of the fields with the lowest levels of vomitoxin, highest yields and test weights were those that received a fungicide application at flowering,” they say.

“However, vomitoxin levels were still higher than 3 ppm in some of the treated fields. Similarly, fields treated for Stagonospora also had better grain yield and quality than fields left untreated. Combining variety resistance with fungicides added a few more bushels to yield and pounds to test weight.

“Another positive from this season was the fact that the scab forecasting system did a good job of alerting us about the risk of scab. We did have more scab in 2010 than we had in 2009 and the risk tool clearly indicated that was going to be the case.”

Manage Disease

 There are a number of things to consider when planning the 2010-2011 wheat crop, the pathologists say.

“Foliar diseases can be managed effectively with resistance or with a well-timed fungicide application if the variety is susceptible, with a percent control as high as 90%. Resistance must be combined with a fungicide application at flowering to achieve the best results in terms of scab and vomitoxin control.”

They also recommend growers give a priority to scab resistance, if a variety with resistance to multiple diseases can’t be found.

“Planting resistant varieties with different flowering dates (maturity) will almost certainly reduce the chance of your entire field being affected by a disease, even if the weather becomes favorable,” the pathologists say.