April 28, 2004 | By: Laura Skillman
PRINCETON, Ky.

Thanks to a cooperative effort, Kentucky ’s wheat farmers will have a new means of combating a wheat disease that can cause tremendous economic losses.

Kentucky has been approved by the U.S. Environmental Protection Agency for a Section 18 Emergency Exemption for 2004 to use Folicur 3.6F to combat Fusarium head blight and deoxynivalenol (DON) accumulation in harvested grain. Head blight and DON are periodic problems in Kentucky and were a problem in the 2003 crop.

This new fungicide tool, when used with other management tactics, will reduce the risk of FHB and DON as long as weather conditions are not highly favorable to FHB and DON during crop flowering and grain fill, said Don Hershman, University of Kentucky Cooperative Extension Service plant pathologist. Management tactics include using high quality seed with known high germination, planting moderately resistant varieties, planting varieties with varying maturity dates, and using crop rotation and tillage.

Hershman and Steve Isaacs, UK agricultural economist, worked along with the Kentucky Department of Agriculture and Kentucky Small Grain Growers Association to gain approval of the Section 18 exemption.

Hershman cautioned that Folicur is not a "silver bullet" for managing head blight and DON. A great deal of research suggests that about 30 percent reduction in FHB symptoms and DON accumulation is a reasonable expectation for winter wheat. Sixty percent control or more has been achieved in rare field studies in the United States , but these are atypical results.

“In other words, do not expect Folicur to provide the same level of head blight/DON control as you have come to expect when fungicides are used to control other wheat diseases,” he said. “The key is to think in terms of disease suppression, not control.”

Nevertheless, Hershman said, a 30 percent reduction in head blight and DON could have a significant economic impact locally, and statewide, if there is a moderate amount in 2004. But he advised that significant losses are likely even where Folicur has been applied if weather conditions favor severe head blight this spring.

The Section 18 allows for a single ground or aerial application of four fluid ounces per acre of Folicur 3.6 F to wheat at full head emergence to very early flowering. Applications cannot be made before full heading or within 30 days of harvest. The Folicur Section 18 applies only to wheat and is good for the period April 20 to May 20, 2004.

The optimal time for application is 25 percent of primary heads, scouted at several random sites in a field, showing anthers, Hershman said.

Excellent fungicide coverage on wheat heads is crucial to achieve the greatest possible disease suppression. When spraying by ground using double swivel nozzles provides the best coverage with twin jet nozzles providing acceptable coverage. Ground speed should not exceed 8 miles per hour.

For aerial application, nozzles should be angled to direct spray 90 degrees to the direction of travel. It is best to spray early in the morning or at other times when heavy dew is present. This will facilitate fungicide coverage on heads.

Many wheat producers will have to decide whether to or not to use Folicur this spring. Delaying application of Folicur to achieve head blight/DON suppression could allow for excessive build-up of other fungal diseases.

Conversely, application of other labeled fungicides before full head emergence will control other diseases, but will have no impact on either head blight or DON. Making both applications, while legal, will be economically difficult to justify, Hershman said.

“In this case, I would advise growers that foliar disease development should take precedence since little is to be gained by suppressing head blight or DON if serious losses are incurred by allowing fungal diseases to develop,” he said.

For more information on this Section 18 and wheat diseases, contact a county Cooperative Extension office. The use of wheat fungicides and application methods will also be discussed by Hershman at the UK Wheat Field Day on May 18 at the UK Research and Education Center in Princeton .

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Contact: 

Writer: Laura Skillman 270-365-7541 ext. 278
Source: Don Hershman, 270-365-7541 ext. 215