Wisconsin Winter Wheat Disease Update – June 23, 2020

Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Septoria leaf blotch on a wheat leaf.

We are now well past the time to apply fungicide on winter wheat in Wisconsin. Anthesis has come and gone and now it is time to scout for the predominant diseases to start planning for harvest. We have not observed any symptoms of Fusarium head blight (FHB or scab) yet, but we will continue traveling and scouting.

We are beginning to observe increasing levels of foliar diseases on winter wheat in the state. Septoria leaf blotch (Fig. 1) is visible in the lower canopy and moving up the canopy in many fields we have been in, as weather remains wet and humid. Fungicide applications for FHB should slow the progress of Septoria leaf blotch up the canopy, but care should be taken to monitor the progress of this disease.

Figure 2. Barley yellow dwarf on winter wheat in Wisconsin. Note the purpled flag leaves.

We are also finding higher than normal levels of Barley yellow dwarf virus (BYDV) in winter wheat (Fig. 2). Levels of BYDV are between 5 and 10% incidence on some varieties in the uniform variety trials. Higher levels may be a result of earlier than normal aphid flights this spring due to mild conditions. Regardless, I don’t think there is a huge amount of concern, as many varieties are resistant and levels observed are still below that at which yield might be reduced.

Finally, we have observed Cephalosporium stripe on wheat at the Arlington uniform variety trial location (Fig. 3). We have seen this disease occurring more frequently in the state over the last couple of seasons. One reason might be shorter rotations between wheat in some fields and potentially increased susceptibility in some varieties. I would say that this season it isn’t severe as far as we have seen, but we will rate the disease and report results if they look meaningful. You will remember that in 2019, we had a severe epidemic of Cephalosporium stripe at our Sharon, WI uniform variety trial location. The severity ratings can be found in the trial report.

Figure 3. Cephalosporium stripe of winter wheat in Wisconsin.

We continue to look for stripe rust in the state. While we have found it at VERY low levels in a couple of locations, we have not seen increased occurrence or severity since the initial observations. Hot and dry weather has kept this disease under control. We will continue to scout wheat in the state and report the results of our observations here. Until then, get out and SCOUT, SCOUT, SCOUT!

Wisconsin Winter Wheat Disease Update – June 28, 2019

Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

The Badger Crop Docs have been busy scouting production wheat fields and University of Wisconsin-Madison winter wheat variety trials and management trials around the wheat growing region of Wisconsin. 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.  Even within plot, variability existed. This variability has resulted in some difficulty in managing diseases.

Fusarium Head Blight Starting to Show Up

Figure 1. Fusarium head blight of winter wheat

We are beginning to see Fusarium head blight (FHB or scab) showing up in many of the locations we have visited. More scab is apparent in the southern locations, especially in the Arlington area. As you might expect it does vary by variety, but in susceptible varieties incidence is running in the 5-10% range, with more expected to become apparent next week. 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 7 days after the start of anthesis. Uneven anthesis across a field can complicate the fungicide application timing, 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. 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. Be sure you are familiar with your elevators dockage policies before hauling loads of grain. Each elevator has different rules and regulations.

What is the Situation with Rusts in Wisconsin on Winter Wheat?

Figure 2. Stripe rust on the flag leaf of winter wheat.

We have observed very low levels of both leaf rust and stripe rust. Stripe rust has been observed at extremely low levels, 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. The late arrival of both of these rusts in Wisconsin will likely result in little yield impact. A fungicide application IS NOT recommended at this point in the season.

Tan Spot is Present At Many Locations

Tan spot has been observed in the lower canopy of wheat at all locations we have visited. The heaviest pressure has been at the Sharon and Arlington locations, with minimal pressure at the Fond du Lac and Chilton locations. Tan spot is remaining in the lower canopy in wheat treated with a fungicide. At Arlington, 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. With that said, a fungicide is NOT recommended at this time of season.

Cephalosporium Stripe Present in Sharon and Fond du Lac

Figure 3. Cephalosporium stripe on winter wheat.

We have also observed Cephalosporium stripe 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 2 seasons at the Fond du Lac location. 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. No in-season management is available for Cephalospyrium stripe. However, noting which fields and locations in fields that have symptoms will help for 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. For more information about Cephalospyrium stripe CLICK HERE AND SCROLL DOWN TO THE CEPHALOSPORIUM STRIPE SECTION.