Fungicide decision nearing for NE Indiana wheat

A potentially serious situation is brewing again this year with wheat in Indiana, with opportunities for many northeast Indiana producers to act in time to protect their crop.

Dr. Kiersten Wise, Purdue plant pathologist, recently posted comments for the Fusarium Head Blight Prediction Center online at wheatscab.psu.edu. According to the website, “The goal of the Fusarium Head Blight Prediction Center is to help growers evaluate the risk of Fusarium head blight in their area. The system uses weather conditions reported for an area to estimate the risk of a severe outbreak of disease. The colors on the map represent the amount risk. A green color indicates the risk of disease is low. The yellow or red colors on the map indicate moderate or high levels of disease risk.”

I will add that if you are having trouble getting the color maps to work on the website, try a different web browser.

On May 4, Wise wrote, “Wheat flowering across southern and central Indiana is at moderate to high risk for Fusarium head blight, according to the latest risk map predictions. Fungicide applications should be applied at early flowering to be most effective. Indiana research indicates that applications of the fungicides Prosaro and Caramba are most effective at managing FHB if they are applied at early flowering (Feekes growth stage 10.5.1). Other products are available, but may not be as effective. If the recent rains or other factors delay application and risk for FHB is high, Purdue University research indicates that fungicides applied a few days after flowering can reduce DON compared to no fungicide application.”

Read updated comments by Wise at the FHB Prediction Center website referenced above, as conditions and associated risk assessments may change.

The common name for Fusarium head blight is scab, or head scab. According to Purdue Extension’s Wheat Field Guide, 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. The disease is caused by the fungus Fusarium graminearum.

According to the Fusarium Head Blight Prediction Center, the fungus attacks the grain directly and can result in serious yield losses. Losses may also be compounded by mycotoxins that are produced by the fungus in diseased grain. Symptoms of 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, so that time will soon be upon us. 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:

• 10.1 – awns visible, grain heads emerging

• 10.3 – heading half complete

• 10.5 – heading complete

• 10.5.1 – beginning flowering (at this growth stage, pollen-containing anthers are visible on the wheat head)

• 10.5.3 – flowering and pollination complete

Wise recommends fungicide treatment at or shortly after Feekes 10.5.1 to minimize the risk of FHB (scab). For farmers considering treatment, scout fields to determine predominant growth stage of wheat to gauge proper timing of fungicide applications.

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 The Education Store, at the-education-store.com.

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