Ohio State Expert: Cold Snap Could Injure Wheat Depending on Its Growth Stage

COLUMBUS, Ohio – Thanks to last month’s warmer-than-normal temperatures that sped up the growth of wheat crops across Ohio, this week’s cold snap could result in injury for some of those plants.

Just how damaging the colder weather will be depends on how advanced the wheat is in its growth stage, said Laura Lindsey, a soybean and small grains specialist with Ohio State University Extension.

Temperatures that reached above 70 degrees across Ohio caused much of the state’s winter wheat crops to progress quickly, Lindsey said, with some areas reporting wheat at Feekes growth stage 5 in March.

This week, some areas in southern Ohio reported wheat crops at Feekes growth stage 6, which is also known as jointing, and some wheat crops in northwest Ohio were already at early green-up in mid-March, she said.

That early wheat growth could leave some growers facing injured crops from the freezing temperatures that have swept across the state since last week, Lindsey said.

“This is a very unusual weather pattern to have a very early spring with temperatures across the state in the low 60s to mid to low 70s throughout much of March followed by this cold snap in April,” she said. “The warmer temperatures caused wheat to come out of dormancy quicker,” leading to the potential for cold-weather injury.

Since April 2, temperatures have reached a low of 29 degrees across parts of Ohio, with the forecast for this weekend to be a low of 20 degrees in many areas statewide, according to AccuWeather.com.

“Winter wheat crops typically experience their maximum resistance to cold weather from December to February,” Lindsey said. “But as wheat greens up, the plant becomes less tolerant of freezing temperatures.

“At jointing, or Feekes 6 growth stage, wheat crops that experience 24 degrees or lower for longer than two hours can sustain injury or freeze damage.”

Lindsey said while there really isn’t anything growers can do to shield their wheat crops from the cold weather, growers should examine their wheat to identify its growth stage to try to judge the crop’s potential for freeze damage. And about a week after injury, growers need to examine their crops to see how much actual plant death there was.

“Once conditions improve, about a week after the crops sustained the freeze injury, growers can go out and examine their wheat fields to see what plants have survived,” she said. “If the plants are at Feekes 5 growth stage, they shouldn’t experience freeze injury, but if they are at Feekes 6 growth stage, it could be a problem.”

Lindsey and Pierce Paul, an OSU Extension plant pathologist and a researcher with the Ohio Agricultural Research and Development Center, are currently conducting research to determine the freeze tolerance of winter wheat grown in Ohio at Feekes 5 growth stage.

OSU Extension and OARDC are the outreach and research arms, respectively, of the college. 

Preliminary results have shown that wheat at that growth stage sustained very little injury at temperatures as low as 14 degrees, Lindsey said. But temperatures of 5 degrees resulted in wilted leaves with a dark, purple-green, water-soaked look 24 hours later, she said.

The team also plans to test wheat plants in Feekes 6 growth stage for freeze damage and expects to update its findings soon.

“Our goal is to be able to update our recommendations for farmers based on our research findings,” Lindsey said. “We really haven’t seen a year like this in recent times, so our recommendation is for growers to go out and check their wheat plants to judge their growth stages.”

• To determine if wheat is in Feekes growth stage 6, growers can:
• Dig up several clusters of tillers with roots and soil from multiple locations in the field.
• Identify and select three to four primary tillers from each cluster – usually the largest tillers with the thickest stem.
• Strip away and remove all the lower leaves, which are usually small and yellowish, or dead leaves, exposing the base of the stem.
• Look for the first node generally between 1 and 2 inches above the base of the stem. This node is usually seen as a slightly swollen area of a slightly different shade of green than the rest of the stem.

A video on identifying Feekes growth stage 6 can also be viewed at youtube.com/watch?v=iukwznx4DPk.