Some winter wheat disease showing up in Wisconsin

Carol Spaeth-Bauer
Wisconsin State Farmer
Fusarium head blight of winter wheat.

Signs of Fusarium head blight (FHB or scab) have shown up in many of the locations scouted by Damon Smith, crops pathologist, and Brian Mueller, assistant field researcher at the University of Wisconsin-Madison.

"Wheat heading and anthesis was very uneven this season. At several locations we visited, we could observe some varieties still in anthesis, while others had finished flowering for some time," the Badger Crop Docs said in a June 28 blog. "Even within plot, variability existed. This variability has resulted in some difficulty in managing diseases."

There is more scab is apparent in the southern locations, especially in the Arlington area and it varies by variety, but in susceptible varieties incidence is running in the 5-10% range, with more expected to become apparent next week.

According to the blog, the primary challenge managing scab this season, has been the uneven anthesis timing. Applications of fungicides for managing scab should begin at anthesis and continue until about seven days after the start of anthesis. However, uneven anthesis across a field can make the fungicide application timing difficult, as some heads might be at the right growth stage while others might be still in the boot or already past anthesis.

"Multiple site-years of research in Wisconsin and the Midwest show that if fungicide is applied before anthesis or 10 days or more after anthesis, poor control of FHB will be achieved with a corresponding unacceptable reduction of vomitoxin," according to the blog. "As we get closer to harvest, it will be important to scout your wheat for scab and determine how much damage is present. Careful harvest and cleaning will be necessary in these fields to make sure vomitoxin limits come in below thresholds where dockage and rejection occur for your elevator."

The Crop Docs recommend becoming familiar with your elevators' dockage policies before hauling loads of grain as each elevator has different rules and regulations.

Stripe rust on the flag leaf of winter wheat.

Rusts on winter wheat

The Badger Crop Doc blog reported low levels of both leaf and stripe rust. 

Stripe rust has been at less than 5% incidence in only one variety at both the Fond du Lac and Sharon uniform variety trial locations.

Leaf rust has been observed at similar levels on several varieties in the Arlington uniform variety trial. With the late arrival of both of these rusts in the state, there is little yield impact expected and a fungicide application is not recommended at this point in the season.

Tan Spot is present 

The situation is not the same with tan spot which has been observed in the lower canopy of wheat at all locations visited. The heaviest pressure has been at the Sharon and Arlington locations, with minimal pressure at the Fond du Lac and Chilton locations, according to the blog.

Tan spot is remaining in the lower canopy in wheat treated with a fungicide. At the Arlington location, wheat in several research trials not treated with fungicide have significant tan spot on the flag leaves. If tan spot has reached the flag leaf at this point, yield may be negatively affected, however, a fungicide is not recommended at this time of season.

Cephalosporium stripe on winter wheat.

Cephalosporium stripe 

Cephalosporium stripe has been seen in both the Sharon and Fond du Lac uniform variety trials.

"This is a newer disease of winter wheat in Wisconsin, but has been observed over the past two seasons at the Fond du Lac location," it said in the blog. "This is the first year we have observed Cephalosporium stripe at the Sharon location. At this location, pressure is uniform and significant on several varieties. We observed incidence ranging from 0 to 90% depending on the variety. We believe that pressure is higher this year due to winter heaving and cool wet conditions this spring."

The bad news is, no in-season management is available for Cephalospyrium stripe. It is recommended to note which fields and locations in fields have symptoms to help with future decisions about winter wheat management in those areas.

Varieties with genetic resistance are available. Also longer rotations and better grassy-weed control can help reduce the severity of Cephalospyrium stripe.