Pre-harvest sprouting in wheat threatens crop

Writer: Kay Ledbetter, 806-677-5608, [email protected]
Contacts: Dr. Clark Neely, 979-845-3041, [email protected]

COLLEGE STATION – The Texas wheat crop was shaping up to have above-average yields across the state, but weather conditions have changed that optimistic outlook in the past few weeks, said a Texas A&M AgriLife Extension Service specialist.

Excessive rains have already prevented some fields from being harvested in South Texas and lodging is quite common across the Blacklands, said Dr. Clark Neely, AgriLife Extension small grains and oilseed specialist in College Station.

With continued chances of rain in the forecast, pre-harvest sprouting is another concern that many growers will have to deal with this year, Neely said.

Pre-harvest sprouting in wheat is not a new phenomenon in Texas, but the number of potential acres affected this year could be very widespread compared to years past, he said.

“Sprouting only becomes an issue once the crop has reached physiological maturity,” Neely said. “Fortunately, regions of Southeast Texas and the Southern Blacklands did not reach maturity until a week or two ago, which provided protection against sprouting from the heavy rains received throughout April and most of May.

“However, wheat in this region has now passed this critical threshold and recent rains are likely to have an impact on the crop.”

When assessing wheat for pre-harvest sprout damage, insurance agents and grain elevator personnel are looking for visual evidence of sprouting. Symptoms can include a visible sprout emerging through the seed coat, a missing germ or cracked seed coat, he said.

Neely warned, however, that chemical changes can occur in the seed before visual symptoms appear and can still cause quality reduction in the seed. Sprouting in wheat kernels leads to a build-up of alpha-amylase in the seed, which converts starch into sugar. This will also reduce test weight as the sugar is turned into energy, water and carbon dioxide by the seedling.

Conversion of starch into sugar also is bad for baking quality, he said. Sugar holds less water than starch and leads to reduced gas retention and causes wet, sticky dough, which is difficult to handle. Bread baked with sprouted wheat will not rise properly, contain large, unattractive gas bubbles, and is difficult to slice.

Neely said rain alone doesn’t cause sprouting; it is a combination of temperature and amount of moisture, as well as the number of wetting and drying cycles. Each time a precipitation event occurs, the seed absorbs water and then dries out. The rate of water uptake increases for each subsequent rain event, which also enhances the chance for sprouting.

“The fact that some fields never dried out in between storms may have been beneficial to some degree,” Neely said.

Various genetic factors also play a role in varietal differences for sprout tolerance. These include seed dormancy, head angle, seed coat color, awned versus awnless and glume tenacity.

If sprouted wheat is harvested, Neely said growers have three main options:

– Market to a grain elevator, where it will incur price discounts, but also could be refused if the percentage of sprouted wheat is too high. For more information on dealing with grain contracts and delivery of sprouted wheat, refer to AgriLife Extension publication titled “Grain Delivery Issues with Cash Grain Contracts” at http://bit.ly/1AIGygA.

– Feed to livestock. For more information on feeding sprouted wheat refer to the AgriLife Extension publication titled “Sprouted Wheat for Feeding Cattle” at http://bit.ly/1d2rSy2.

– Saving seed to plant, although reduced germination and seedling vigor of sprout damaged wheat can significantly reduce stands when planting the following year.

Seed with a split seed coat can still germinate if stored under ideal conditions; however, seed with visible plant parts should not be used, Neely said. If sprouting is suspected in wheat, even if visible signs are not obvious, it is highly recommended to conduct a germination test.

A list of official seed testing laboratories can be found at http://bit.ly/1eAMmiq.

“Looking ahead, some fields in the Rolling Plains already reached maturity last week, while later fields are likely to finish this week,” Neely said. “Much of this region received another 1-2 inches of rain over the past few days; however, conditions are expected to improve for much of this week and may provide a harvest window.”

He said under these circumstances, a difference of one or two days in maturity could be crucial in whether a field develops pre-harvest sprouting.

Much of the High Plains wheat crop is past flowering, but weeks away from harvest, so recent rains may have helped yields and test weights and do not pose a threat of sprouting at this time, Neely said.

Additional information on pre-harvest sprouting in wheat can be found in the AgriLife Extension publication, “Pre-Harvest Sprouting in Wheat,” at http://bit.ly/1SF3SBU.