As wheat matures and approaches flowering in the southern part of Indiana, growers need to be on the look out for Fusarium head blight, or scab.
The fungus that causes head scab, Fusarium graminearium, infects wheat during flowering, beginning at growth stage Feekes 10.5.1, said Purdue Extension plant pathologist Kiersten Wise. Symptoms include bleached spikelets on the head and small or shriveled grain kernels commonly referred to as "tombstones."
The fungus also produces mycotoxins, such as deoxynivalenol, or DON, which can accumulate in infected grain. If consumed, mycotoxins can cause health problems in livestock and humans.
Rainy, warm and humid weather conditions tend to favor disease development.
"The recent rains may have triggered spore production, and if the wet, humid weather continues as the majority of wheat in southern Indiana begins to flower, it is possible that a fungicide application will be necessary to suppress Fusarium head blight," Wise said.
Farmers who know the approximate flowering date of their wheat varieties can use Penn State University’s risk assessment tool at http://www.wheatscab.psu.edu/ to determine the if a fungicide application is warranted for Fusarium head blight management.
One way growers can preventatively reduce the risk of Fusarium head blight in their wheat crops is to select partially resistant varieties, but Wise said timely and proper fungicide applications often are needed to suppress the disease in-season.
"Applications of fungicide prior to head emergence, such as those applied at jointing for flag leaf emergence, will not reduce head scab infection," she said. "Farmers need to be sure to follow label restrictions on how many days must pass between fungicide application and harvest."
A list of fungicides available for Fusarium head blight control are listed in the foliar fungicide efficacy table on the Purdue Plant and Pest Diagnostic Laboratory website at