Beware of fusarium head blight in wheat; conditions right

As the wheat crop goes into the flowering stage, growers need to monitor local conditions for the fungus Fusarium graminearum, more commonly known as head scab, said a Purdue University expert.

"We've had a lot of rain and high humidity in Indiana as wheat begins to flower," said Kiersten Wise, Purdue Extension field crops disease specialist. "These conditions favor head scab development, and farmers need to be deciding whether or not to apply a fungicide to suppress head scab."

The Fusarium Head Blight Risk Assessment Tool, online at http://www.wheatscab.psu.edu/riskTool_2009.html, provides growers with local conditions and assesses risk for the development of head scab. The tool, hosted by Kansas State University, can assess area risk for the current time and in 24-hour increments up to 72 hours.

The fungus causing head scab overwinters in last year's crop residue and wind and rain move the spores into wheat, Wise said. The disease doesn't infect the plant leaves, but infects the wheat head, giving it a bleached look. The fungus produces toxins, specifically DON, which are harmful if consumed by livestock, especially swine, she said. Also if toxin levels are too high, growers may receive discounted prices at the elevator.

"Wheat is most susceptible to head scab at the flowering stage, and growers should apply fungicide at early flowering to suppress head scab," Wise said. "Farmers should scout fields to determine the exact growth stage of the wheat crop. If a fungicide application is needed, apply at Feekes 10.5.1."

A list of fungicides to suppress head scab is available at
http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/
OFCDwheatfungicides.pdf, but Wise warned they vary in their ability to suppress scab development. She also encourages farmers to read the label and make note of the preharvest interval.

"We don't have a silver bullet for head scab," Wise said. "So even with fungicides, you may still see head scab in your fields."

To date, more than 6,000 acres have been sprayed in southern Indiana, where the wheat crop started flowering during the first weekend of May, Wise said. Head scab has been identified in Indiana research trials, and Wise will be travelling to Posey, Sullivan and other southern counties to scout fields and better assess the situation.