Perfect storm brewing for Fusarium Head Blight of wheat in southern Illinois

Continuing rainfall in southern Illinois has literally created the "perfect storm" for one of the most devastating diseases of wheat — Fusarium head blight (FHB or scab), said University of Illinois Extension plant pathologist Carl Bradley.

"FHB can cause both yield and quality losses," Bradley said. "Quality losses can be due to lower test weights and contamination of grain by toxins produced by the fungus that causes FHB. Because the fungal pathogen that causes Fusarium head blight, Fusarium graminearum, also causes Gibberella stalk and ear rot of corn, the pathogen is almost always present throughout Illinois surviving on corn debris."

On April 27, most of southern Illinois was listed under medium to high risk of FHB, according to the FHB risk assessment tool (available at www.wheatscab.psu.edu). Only wheat fields that have headed out and are flowering are at risk of infection by the FHB fungus. Some wheat fields in southern Illinois will likely be heading or flowering this week or next week, he added.

"For fields that will be flowering this week, a foliar fungicide for suppression of FHB and the associated mycotoxin deoxynivalenol (DON) is recommended for fields in the medium-to-high risk areas," Bradley advised. "The only fungicides that are effective in providing respectable levels of FHB and DON suppression are Caramba, Prosaro, and Folicur (and other tebuconazole products)."

Research conducted by the U of I as well as other universities has shown that Caramba applied at 13.5 fl oz/A and Prosaro applied at 6.5 fl oz/A are more effective at suppressing FHB and DON than Folicur applied at 4 fl oz/A. The highest level of FHB and DON suppression will be achieved with foliar fungicides when they are applied at Feeke's growth stage 10.5.1 (early anthesis — when anthers are beginning to extrude from the middle part of the head).

Foliar fungicides are the only "in-season" control option for FHB and DON; however, one of the best management practices for FHB and DON is choosing to plant a variety with a moderate level of FHB resistance, Bradley said. Integrating management practices such as planting a moderately resistant variety and spraying a foliar fungicide, if needed, will provide the highest level of FHB and DON suppression.

"For fields that will be flowering next week, it is important to monitor the FHB risk assessment tool," he said. "If the rain stops and sunny and dry conditions occur next week, then the risk of FHB will decrease."