Drought stress and genetics impacting wheat fungicide performance

(Kara Oosterhuis/RealAgriculture)

There’s plenty of research data that shows applying a T3 fungicide to winter wheat will deliver a yield benefit, even in a dry growing season.

RealAgriculture agronomist Peter Johnson says dry growing conditions tend to drive down fusarium head blight and other disease pressure, resulting in less yield loss, but the fungicides also increase the stay-green impact and overall plant health, which drives grain fill and better yields.

Based on research work done by University of Guelph field crop agronomist and associate professor Dr. Dave Hooker, even when soil moisture is in short supply, the fungicide application will deliver an average 5.5 bu/ac return.

But the 2023 growing season appears to be throwing some curves at this year’s crop and the impact of fungicide applications. On the Agronomic Monday edition of RealAg Radio, Johnson reported that in some fields in Ontario, fungicide application appears to be contributing to higher levels of leaf tip necrosis.

Johnson says the issue appears to be related to specific wheat varieties as well as severe drought stress. “Certain varieties are just subject to leaf tip necrosis — the tips of the leaves basically turn brown and they die,” he says. “It’s related to rust resistance. The varieties that had seemed to have better rust resistance tend to have more of this leaf death.

See Related: Wheat School: Do T3 fungicides pay in a dry year?

“We’re used to seeing a little bit of that leaf tip necrosis, but [this year] if that wheat field was under significant stress and you sprayed it with a fungicide, the amount of damage you got on the flag leaf was just harsh. And a lot of fields went from looking green as grass to looking very brown and yellow and not good at all,” Johnson adds.

This type of injury is not new to Ontario wheat  growers, Johnson notes. The damage may look extensive and growers may be expecting a big yield hit but overall yield loss is relatively small. “Most of the time, we just lose the benefit of the fungicide,” he notes. “You lose that six bushels and you might lose another three, four or five bushels, but it’s not the 50 bushel yield hit that you think it is.”

(Listen to the full report below with Johnson and RealAg Radio host Shaun Haney.)

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