Summer rains could mean sprout damage for wheat crops


By Seth Truscott, College of Agricultural, Human & Natural Resource Sciences

PULLMAN, Wash. – Summer rains interrupted Washington’s heat wave last weekend, but more damp days could cause problems for some of the state’s wheat farmers.

For wheat crops close to harvest, rainfall can lead to sprout damage – the unwanted germination of kernels that drastically affects the quality of flour.

“The longer the plant stays wet, the more chance there is for sprout damage,” said Arron Carter, winter wheat breeder at Washington State University (

Lower elevations vulnerable

On July 10 and 11, the WSU AgWeatherNet monitoring system ( recorded scattered rainfall east of the Cascades. At Pullman, an automated weather station recorded 0.26 inches of rain on July 10.

Wheat-Spillman-webFairfield, Wash., south of Spokane, saw 0.19 inches of rain on July 11. Anatone, Wash., south of Asotin, had the most rain, with 0.83 inches on July 11.

While winter wheat in the higher Palouse area is still somewhat green, said Carter, wheat at lower elevations may be closer to maturity and more vulnerable.

“If wheat was harvest ready, an inch of rain may cause problems,” he said.

Enzyme breaks down starch

When wheat kernels germinate, they release higher levels of the enzyme alpha-amylase. That enzyme breaks down starch in the kernel, causing reduced baking quality in flour.

“A lot depends on the variety and the weather,” said Carter. “If there is a little rain in a quick period, and then it gets hot again, there isn’t much concern.”

But more rain over a longer period, coupled with cool weather, could mean trouble.
Cool, wet nights may increase the damage by breaking dormancy in seeds, allowing them to germinate more readily.

“Varieties also make a difference,” Carter said. “Some wheat breeds germinate very quickly with a little bit of rain; others seem to stay dormant.”

Minimal drought relief

The rain may be good news for farmers who rely on rainfall for soil moisture, said AgWeatherNet meteorologist Nic Loyd. However, it won’t end Washington’s drought.

“We would need much longer term relief from the recent hot, dry weather and more significant and widespread rainfall for any meaningful drought mitigation,” said Loyd.  “The long term outlook is still hot and somewhat dry for the next 12 months or so.”

Forecasts predict rain later this week in areas including Pullman, Ritzville, Spokane and Colville, Wash.

• Learn more about the WSU Department of Crop and Soil Sciences at
• Learn more about Washington’s drought at


Arron Carter, WSU winter wheat breeder, 509-335-6198,
Nic Loyd, WSU AgWeatherNet meteorologist, 509-786-9357,