As the snow melted from eastern Washington wheat fields, a surprise emerged. Snow mold in the fields damaged the crop, which surprised a Washington State University plant expert who has studied the fungus for nearly 40 years.

As the snow melted away, areas of injured wheat appeared in parts of the state where such damage is rarely seen. WSU plant pathologist Tim Murray recently met with 20 growers in Prescott, Wash., to address their concerns. In a release from WSU, Murray commented: "Growers in this area have never seen this mold until now. Its presence may have surprised me, but it really surprised them."

An examination of a half-dozen fields in south-central and southeastern Washington showed damage ranging from nonthreatening lesions on leaves to underground crown decay that kills the crop. Added Murray: "I was surprised to see how prevalent the damage was in some of the fields," he said. "We'll definitely be seeing some economic damage as a result." He added that the extent of the damage can't be measured until soils are warm enough to reveal which plants survived and which did not.

Understanding pink fungus
Pink snow mold is a cold-loving organism that thrives under long periods of snow cover. Called pink mold, it attacks perennial plants and overwintering crops. The mold is more commonly seen in the highest elevations of north-central Washington, where snow blankets the ground for 100 days or more.

Pervasive snow this winter fueled the mold's growth in lower elevations, too, Murray said, including Walla Walla, Whitman and Columbia counties. Caused by the fungus Microdochium nivale, the pink-tinged mold is showing up in fields of winter wheat — and even lawns.

Murray explained that snow serves a purpose: insulating winter wheat and other dormant plants from cold temperatures. "But the snow cover becomes a problem when it stays on the ground for too long, which is just what happened," he said.

In areas where damage has been found, snow cover was on the ground for 60 to 70 days. That's longer than most years, but Murray said that "it's still not long enough to cause the kind of damage I've been seeing. It typically takes at least 100 days."

Why the higher amount of mold? Murray explained that abnormally warm temperatures in November kept the ground from freezing before the first hard snow arrived, creating a more hospitable environment for the mold to form. Combine that with the longer-than-usual period of snow cover, and the mold had just what it needed to thrive.

Advice for growers
Murray has spent 40 years developing high-quality wheat varieties that defend against snow mold and other disease. Microdochim nivale is one of the three fungi that cause snow mold in Washington.

Murray advises growers to let a few weeks of warmer weather pass in order to assess the full impact of damage to their fields. At that point, they can decide whether reseeding is necessary.

Source: Washington State University