Orville’s winter wheat looked lush and uniform in the spring, but as the flag leaf emerged, it yellowed in the entire crop within five days. Orville wanted to act quickly and apply a fungicide to battle what he was certain was a disease problem.
I convinced him to take the time to consider other options, including his nitrogen. Despite a manure application which offered 50 lbs. of nitrogen and 40 lbs. applied in the spring, we thought maybe there just wasn’t enough.
Upon closer inspection, the yellowing in his winter wheat was limited to the flag leaf, which was about half-way emerged from the boot. The rest of the plant below the flag leaf was coming in nicely.
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We decided not to apply more nitrogen because some disease damage was making its way up the plants. Orville continued through with our original fungicide program, even though the damage appeared already done.
On the day Orville planned to apply the fungicide I joined him. A big surprise awaited us when we went in for one last close inspection. As plain as day, there was a direct line across each flag leaf. As soon as Orville saw it, the mystery was solved.
“Those huge winds in June! The flag leaf was making its way out of the boot when we got those winds and then it was hot.”
I had to agree. There was a visible line between the healthy and unhealthy portions of the flag leaf. Bent right over in the wind, the newly emerging flag leaves had been creased, which of course reduced the nutrients’ ability to deliver. The flag leaf feeds almost all of the nutrition the head requires. If the flag leaf is unhealthy, you’re stepping on the garden hose and wondering why you can’t apply your water. In the following heat, the head leaves had been scorched to yellow.
Only because this crop was so even and beautiful could we have sorted out the problem with Orville’s winter wheat. Disease can’t usually take hold in as little as five days.
Orville looked to be reaching 65 bu./ac. for his wheat and we were seeing about 16 spikelets per spike. He decided to follow through with his fertility program and apply the fungicide.
Use common sense and don’t panic. If you’ve got fertility and fungicide programs in place, stick to those plans. Orville could have sunk a whole lot of money thinking we were low on nitrogen. Not only that, if we’d put the fungicide on immediately when Orville wanted to, it would have only hit the yellowed damaged part of the leaf. The healthy part would have been open to disease. You don’t want to jump to conclusions and spend money you don’t have to. Take the time to diagnose a problem correctly.
Terry Moyer is an agronomy sales manager for Pioneer Grain and Landmark, Man.
