As we approach heading and flowering time in wheat, early flowering is the time to consider spraying fungicides to protect wheat from Fusarium Head Blight (FHB, or scab).
Dr. Darcy Telenko, Purdue Extension field crops pathologist, reported on May 9 that wheat was starting to head out across central and northern Indiana, with flowering not too far behind. “Our plots in southern Indiana hit early anthesis (flowering) last week and we put out our Feekes 10.5.1 fungicide trials out at Southwest PAC, Vincennes, IN,” she said. “The wheat was 50% flower.” She added that rainy, wet conditions can favor many fungal diseases in wheat. “Our southern neighbors have started reporting multiple diseases in wheat,” she said. “These include – strip and leaf rust. They also found Septoria leaf spot in the lower canopy in our southwest plots.”
The Fusarium Head Blight Prediction Center, housed at Penn State University, produces daily risk maps that indicate low, medium, or high-risk areas for scab development in the Midwest. Find the information at http://www.wheatscab.psu.edu/.
“Looking at the Fusarium Risk Tool [for] wheat scab risk there are a number of areas starting to move into medium risk, there are also some areas that are red if wheat is planted to a susceptible cultivar,” said Telenko. “The risk is reduced if the cultivar is moderately susceptible or moderately resistant to Scab where most of Indiana remains in the low risk.”
Purdue Extension’s Wheat Field Guide states that this fungus survives through the winter in infected corn residue. High humidity and frequent rainfall promote the production and dispersal of spores from residue. The wind can blow spores onto wheat plants. Warm, humid weather promotes infection and secondary spread.
According to the Fusarium Head Blight Prediction Center, the fungus attacks the grain directly and can result in serious yield losses. Symptoms of the disease include tan or brown-colored lesions that may include single spikelets or large sections of the wheat head.
Flowering dates will generally occur chronologically from southern Indiana to northern Indiana. Feekes 10 is the general term for the boot stage of wheat, where the developing grain head swells and is visible in the leaf sheath directly below the flag leaf. The further decimals refer to various sequential growth stages of wheat. Feekes 10.5.1 refers to the beginning flowering growth stage of wheat. Purdue Extension publication ID-448, Wheat Field Guide, describes these stages:
“Keep in mind that actual disease risk depends heavily on the growth stage of wheat in your area,” said Telenko. “We are approaching a critical time here in Indiana.” She said that these risk estimates are most relevant just prior to flowering (Feekes 10.5.1) or the early stages of grain development. “Fusarium head blight risk is highest when there are three or more days with extended periods of high relative humidity and moderate temperatures (65 to 80°F) during the early stages of kernel development,” she said.
Telenko advised growers that a fungicide application might be considered if a Fusarium head blight (FHB) susceptible variety is planted, or if you are worried about scab on your farm. “These applications should be made at Feekes 10.5.1, or early flowering to suppress FHB,” she said. “Fungicides recommended for FHB and DON include Prosaro, Proline, Miravis Ace, and Sphaerex. The use of products containing strobilurin fungicides may result in higher levels of DON accumulation in grain when damaged by FHB. These are not labeled for FHB management.”
Find the full May 9, 2024 article by Telenko in the Purdue Plant & Pest newsletter: https://extension.entm.purdue.edu/newsletters/pestandcrop/article/fusarium-head-blight-scab-and-wheat-update/.
More information is available by accessing the free publications, “Managing Wheat by Growth Stage,” ID-422-W, and “Fusarium Head Blight (Head Scab),” BP-33-W, available online at Purdue Extension’s Education Store, www.edustore.purdue.edu. Find additional information from the Crop Protection Network at https://cropprotectionnetwork.org/.