COLUMBUS – As Ohio’s winter wheat races to flag-leaf emergence, growers should closely watch the crop in order to treat effectively for powdery mildew, said Pat Lipps, plant pathologist at Ohio State University.
“Powdery mildew is present in certain fields of susceptible varieties in north central and northeast sections of the state,” Lipps said.
“In some cases powdery mildew is already on the second leaf. Make applications as soon as possible so disease does not advance any further.”
Lipps said much of northern Ohio’s wheat is in flag-leaf emergence, or Feeke’s growth stage 8, a critical time for treating wheat for powdery mildew.
Losing yield. In the south, some fields are well on their way to booting – Feeke’s 10. Susceptible varieties can lose 16 percent yield when powdery mildew reaches the leaf below the flag, and can lose 25 percent yield when infections reach the flag leaf.
Farmers can apply Tilt at 4.0 ounces per acre to control powdery mildew, Lipps said. Tilt can be applied through flowering of the crop.
Apply a fungicide if infections have reached the leaf below the flag on 30-50 plants randomly selected from a field. Expect disease to spread if temperatures remain in the 60-70 degree range and relative humidity remains high.
Useful resource. A list of varieties and their reaction to powdery mildew appears online at www.ag.ohio-state.edu/%7Eohioline/iwy/tab5.html.
Also helpful is OSU Extension Bulletin AC-10-96, “Powdery Mildew of Wheat,” available at local Extension offices or online at http://ohioline.osu.edu/ac-fact/0010.html.
Relatively dry weather has generally limited Ohio’s wheat diseases, Lipps said. But one worth scouting for is Stagonospora nodorum leaf and glume blotch – formerly Septoria – showing up on the lowest leaves in some plants.
This disease will become important if it rains several days for each of the next few weeks.
Symptoms include narrow yellow halos, tan centers and a dark brown central area.
Another problem, frost-heaved wheat fields, will show signs of plant death as soils continue to dry, Lipps said.
“The new root systems of heaved plants are not able to support the quickly growing tillers when soil moisture is limited,” he said.
Ohio harvest should start the first week of July.
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