Don’t let Fusarium Head Blight Keep You Down – Prepare Now to Harvest Those Scabby Wheat Fields

Damon L. Smith, Extension Field Crops Pathologist, University of Wisconsin-Madison
Shawn P. Conley, Extension Soybean and Small Grains Agronomist, University of Wisconsin-Madison

Figure 1. FHB on some wheat heads. Note the bleached and reddened appearance of infected kernels.

Fusarium head blight (FHB) or scab has been observed at moderate to high levels in some Wisconsin winter wheat fields this season. Incidence and severity have been variable by location, susceptibility of the wheat variety, and if a fungicide was applied at or shortly after anthesis. Generally, we have observed more FHB in the southern and south-central wheat growing areas of the state, but it can be found just about everywhere we have visited this year. It is important to scout your maturing wheat crop and consider how much damage from FHB might be in a field as you prepare for harvest. While FHB can cause direct yield loss, the fungus that causes this disease can also produce deoxynivalenol (also known as DON or vomitoxin). Assessing wheat fields now can assist you in determining how much vomitoxin might be expected at harvest. However, it is possible to find high levels of vomitoxin in finished grain, even if FHB levels where low.

What does scab look like? Diseased spikelets on an infected grain head die and bleach prematurely (Fig. 2).  Healthy spikelets on the same head retain their normal green color.  Over time, premature bleaching of spikelets may progress throughout the entire grain head.  If infections occur on the stem immediately below the head, the entire head may die.  As symptoms progress, developing grains are colonized causing them to shrink and wrinkle.  Often, infected kernels have a rough, sunken appearance, and range in color from pink or soft gray, to light brown. As wheat dries down, visual inspection of heads for scab will become more difficult.

Figure 2. Fusarium head blight of winter wheat

Why is identifying scab important? Scab identification is important, not only because it reduces yield, but also because it reduces the quality and feeding value of grain.  In addition, the FHB fungus may produce mycotoxins, including DON or vomitoxin, that when ingested, can adversely affect livestock and human health.  The U.S. Food and Drug Administration has set maximum allowable levels of DON in feed for various animal systems, these are as follows: beef and feedlot cattle and poultry < 10ppm; Swine and all other animals < 5ppm. In addition, local grain elevators test for DON and discount loads of grain for unacceptable levels of the mycotoxin. Be sure to check with your local elevator about their thresholds for docking grain and discount schedule based on the level of DON detected BEFORE you bring a load for delivery.

What should I do to prepare for wheat harvest?

  1. Scout your fields now to assess risk. Wheat is maturing rapidly. As maturity progresses it will be increasingly difficult to assess the incidence and severity of the infection. Understanding a field’s risk will help growers either field blend or avoid highly infected areas so entire loads are not rejected.
  2. DO NOT spray fungicide now. Research has demonstrated that the window of opportunity to manage FHB with fungicides is at the beginning of anthesis and only lasts about 7 days. Applications later than 7 days after the start of anthesis are not effective in controlling FHB. In addition, most fungicide labels do not allow a pre-harvest interval (PHI) suitable for a late application on wheat. Any application now would be off-label.
  3. Adjust combine settings to blow out lighter seeds and chaff. Salgado et al. 2011 indicated that adjusting a combine’s fan speed between 1,375 and 1,475 rpms and shutter opening to 90 mm (3.5 inches) resulted in the lowest discounts that would have been received at the elevator due to low test weight, % damaged kernels, and level of the mycotoxin deoxynivalenol (DON; vomitoxin) present in the harvested grain.
  4. Know your elevators inspection and dockage procedure and discount schedule (each elevator can have a different procedure and discount rate).
  5. Scabby kernels does not necessarily mean high DON levels and vice versa. For example, in a 2014 fungicide evaluation very low visible levels of FHB were observed for all treatments. However, when the finished grain was tested for DON, significant levels were identified for all treatments. Be sure to test and know what levels of DON are in your grain even if you didn’t see a high level of visible disease. Also, don’t assume that because a fungicide was used, there will be no DON.
  6. DON can be present in the straw so there is concern regarding feeding or using scab infected wheat straw.  DO NOT use straw for bedding or feed from fields with high levels of scab (Bissonnette et al., 2018; Cowger and Arellano, 2013). If in doubt, have the straw tested for DON levels.
  7. Do not save seed from a scab-infected field. Fusarium graminearum can be transmitted via seed. Infected seeds will have decreased growth and tillering capacity as well as increased risk for winterkill.
  8. Do not store grain from fields with high levels of scab.  DON and other mycotoxins can continue to increase in stored grain.
  9. Harvest in a timely fashion to minimize elevator discounts and balance dockage due to FHB. Click here to read about some recent research on optimizing harvest timing in winter wheat.
  10. For more information on Fusarium head blight click here.

References

  1. Bissonnette, K.M., Kolb, F.L., Ames, K.A., and Bradley, C.A. Effect of Fusarium head blight management practices on mycotoxin accumulation of wheat straw. Plant Dis. 102:1141-1147.
  2. Cowger, C., and Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology 103:460-471.
  3. Salgado, J. D., Wallhead, M., Madden, L. V., and Paul, P. A. 2011. Grain harvesting strategies to minimize grain quality losses due to Fusarium head blight in wheat. Plant Dis. 95:1448-1457.

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.

 

Wisconsin Winter Wheat Disease Update – June 4, 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

Wheat heads are close to emergence on some earlier varieties of winter wheat in southern and south-central Wisconsin. Within the next week wheat heads will be emerging and anthesis (flowering) will be starting, with later varieties to follow. Now is the time to prepare for Fusarium head blight (FHB or scab) management. The Fusarium head blight Risk Model (http://www.wheatscab.psu.edu) is showing moderate to high levels of risk in the primary wheat growing region of the state over the next 72 hours (Figure 1). Pay close attention to the risk model and your local weather as we approach anthesis (flowering). I anticipate the risk to remain high as periods of rain and humidity persist. Fungicide products of choice to control FHB in Wisconsin include Caramba, Prosaro, and Miravis Ace. Multiple years of data in Wisconsin suggest that the best application window for any of these products begins at the start of anthesis until 5-7 days after the start of anthesis. Applying fungicide before anthesis or more than 7-10 days after anthesis will result in poor performance against vomitoxin accumulation. For information pertaining to recent fungicide studies on winter wheat in Wisconsin, CLICK HERE and scroll to page 12. Other reports can be found by CLICKING HERE.

Figure 1. Fusarium Head Blight Prediction Center 72-hour Outlook for Wisconsin.

Wisconsin Winter Wheat Disease Update – May 31, 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 University of Wisconsin-Madison Field Crops Pathology crew has spent the last several days scouting winter wheat variety trials and commercial wheat fields in south and south-central Wisconsin. Wheat at all locations observed had flag leaves fully emerged. Weather has been extremely wet and cool across the state. Despite the wet conditions, wheat was generally disease free in all locations visited.

In Sharon, WI wheat looked decent despite challenging winter and spring conditions. The stand was a bit uneven in terms of growth stage, but most varieties looked good. It won’t be a record yield year, but stands look better than anticipated at this location. Wheat at the Arlington location in central Wisconsin looked very good with strong stands combined with even growth stages across varieties. I anticipate yields to be decent. At the Fond du Lac location wheat was in okay shape, however several varieties did experience significant winterkill. Stands were like those in Sharon, with uneven growth stages within varieties.

Figure 1. Fusarium head blight prediction for May 31, 2019

While disease on wheat has been relatively non-existent in Wisconsin, weather has been extremely wet across the state. Considering these conditions, we are worried about the risk for Fusarium head blight (FHB) this year given the weather pattern we have been stuck in. Currently, the Fusarium head blight Risk Model (http://www.wheatscab.psu.edu) is showing mostly high levels of risk in the primary wheat growing region of the state (Figure 1). While no heads have emerged, heading will begin in the next 1-2 weeks. Pay close attention to the risk model and your local weather as we approach anthesis (flowering). I anticipate the risk to remain high as periods of rain and humidity persist. Fungicide products of choice to control FHB in Wisconsin include Caramba, Prosaro, and Miravis Ace. Multiple years of data in Wisconsin suggest that the best application window for any of these products begins at the start of anthesis until 5-7 days after the start of anthesis. Applying fungicide before anthesis or more than 7-10 days after anthesis will result in poor performance against vomitoxin accumulation. For information pertaining to recent fungicide studies on winter wheat in Wisconsin, CLICK HERE and scroll to page 12. Other reports can be found by CLICKING HERE. Flag leaves are out, get out and scout!

Don’t lose your head over Fusarium head blight: What to do as you prepare for wheat harvest

Damon L. Smith, Extension Field Crops Pathologist, University of Wisconsin-Madison
Shawn P. Conley, Extension Soybean and Small Grains Agronomist, University of Wisconsin-Madison

Figure 1. FHB on some wheat heads. Note the bleached and reddened appearance of infected kernels.

Fusarium head blight (FHB) or scab has been observed in some Wisconsin winter wheat fields this season. Incidence and severity have been variable this season, based on location and susceptibility of the wheat variety. Generally, we have observed more FHB in the southern wheat growing areas of the state, with less FHB as we moved north and east. Visit my previous post for a full report. It is important to scout your maturing wheat crop and consider how much damage from FHB might be in a field as you prepare for harvest. While FHB can cause direct yield loss, the fungus that causes this disease can also produce deoxynivalenol (also known as DON or vomitoxin). Assessing wheat fields now can assist you in determining how much vomitoxin might be expected at harvest. However, it is possible to find high levels of vomitoxin in finished grain, even if FHB levels where low.

Figure 2. Bleached heads caused by Fusarium head blight of winter wheat

What does scab look like? Diseased spikelets on an infected grain head die and bleach prematurely (Fig. 2).  Healthy spikelets on the same head retain their normal green color.  Over time, premature bleaching of spikelets may progress throughout the entire grain head.  If infections occur on the stem immediately below the head, the entire head may die.  As symptoms progress, developing grains are colonized causing them to shrink and wrinkle.  Often, infected kernels have a rough, sunken appearance, and range in color from pink or soft gray, to light brown. As wheat dries down, visual inspection of heads for scab will become more difficult.

Why is identifying scab important? Scab identification is important, not only because it reduces yield, but also because it reduces the quality and feeding value of grain.  In addition, the FHB fungus may produce mycotoxins, including DON or vomitoxin, that when ingested, can adversely affect livestock and human health.  The U.S. Food and Drug Administration has set maximum allowable levels of DON in feed for various animal systems, these are as follows: beef and feedlot cattle and poultry < 10ppm; Swine and all other animals < 5ppm.

What should I do to prepare for wheat harvest?

  1. Scout your fields now to assess risk. Wheat is maturing rapidly. As maturity progresses it will be increasingly difficult to assess the incidence and severity of the infection. Understanding a field’s risk will help growers either field blend or avoid highly infected areas so entire loads are not rejected.
  2. DO NOT spray fungicide now. Research has demonstrated that the window of opportunity to manage FHB with fungicides is at the beginning of anthesis and only lasts about 7 days. Applications later than 7 days after the start of anthesis are not effective in controlling FHB. In addition, most fungicide labels do not allow a pre-harvest interval (PHI) suitable for a late application on wheat. Any application now would be off-label.
  3. Adjust combine settings to blow out lighter seeds and chaff. Salgado et al. 2011 indicated that adjusting a combine’s fan speed between 1,375 and 1,475 rpms and shutter opening to 90 mm (3.5 inches) resulted in the lowest discounts that would have been received at the elevator due to low test weight, % damaged kernels, and level of the mycotoxin deoxynivalenol (DON; vomitoxin) present in the harvested grain.
  4. Know your elevators inspection and dockage procedure (each elevator can have a different procedure).
  5. Scabby kernels does not necessarily mean high DON levels and vice versa. For example, in a 2014 fungicide evaluation very low visible levels of FHB were observed for all treatments. However, when the finished grain was tested for DON, significant levels were identified for all treatments. Be sure to test and know what levels of DON are in your grain even if you didn’t see a high level of visible disease. Also, don’t assume that because a fungicide was used, there will be no DON.
  6. DON can be present in the straw so there is concern regarding feeding or using scab infected wheat straw.  DO NOT use straw for bedding or feed from fields with high levels of scab (Cowger and Arellano, 2013). If in doubt, have the straw tested for DON levels.
  7. Do not save seed from a scab-infected field. Fusarium graminearum can be transmitted via seed. Infected seeds will have decreased growth and tillering capacity as well as increased risk for winterkill.
  8. Do not store grain from fields with high levels of scab.  DON and other mycotoxins can continue to increase in stored grain.
  9. Harvest in a timely fashion to minimize elevator discounts and balance dockage due to FHB. Click here to read about some recent research on optimizing harvest timing in winter wheat.
  10. For more information on Fusarium head blight click here.

References

  1. Cowger, C., and Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology 103:460-471.
  2. Salgado, J. D., Wallhead, M., Madden, L. V., and Paul, P. A. 2011. Grain harvesting strategies to minimize grain quality losses due to Fusarium head blight in wheat. Plant Dis. 95:1448-1457.

Wisconsin Winter Wheat Disease Update – June 26, 2018

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. Fusarium head blight of winter wheat

The Wisconsin Field Crops Pathology crew has scouted and rated all winter wheat variety trials across the wheat-growing region of the state. We have also looked at commercial fields for disease in the region. In general leaf diseases will be of minimal impact this season. We have observed a little Septoria leaf blotch in some fields in the lower canopy. However, this pathogen will not limit yield this season, as it has not reached the flag leaf yet. We have also not observed any stripe rust this season. As I mentioned in previous posts, the winter was cold enough with minimal snow cover, which didn’t allow the stripe rust pathogen to overwinter in the region. Subsequent spread from the southern states north, was also not fast enough to reach the crop in Wisconsin to impact yield. If stripe rust does arrive this season, it will not impact yield. Leaf rust was observed at the Arlington (south-central Wisconsin) location. However, it was at very low incidence and severity and will likely not impact yield on most varieties in the state.

Figure 2. Fusarium head blight index of winter wheat in small plots where fungicide programs were used in 2014.

Fusarium head blight (FHB; scab) has been observed at all locations visited. Incidence and severity is highly variable based on location. At the Sharon (southern Wisconsin) and Arlington locations, FHB could be found in some plots at incidence levels as high as 50% with 50% severity. Many plots had low levels of FHB, thus the average levels at these locations was around 10% incidence with severity levels of around 20%. As we moved north and east in Wisconsin, FHB was at much lower incidence and severity levels. Incidence averaged 5%-10% with severity around 15% at the Chilton and Fond du Lac locations. Commercial fields that we have scouted in these regions fall within these same averages.

Figure 3. Vomitoxin levels of finished grain from winter wheat small plots where fungicide programs were used in 2014.

While I don’t think the FHB epidemic in 2018 will be as bad as 2015, I think it is important to scout fields and understand the levels of FHB present. It will also be important to test finished grain for vomitoxin or DON. Often, the level of visible FHB damage does not reflect the vomitoxin levels of harvested grain. This happened in some fields in 2014, including a research trial that we had at the Arlington location. FHB index levels on heads in the field were very low across all treatments in our research trials that year (Fig. 2). However, when the finished grain was tested for vomitoxin, levels were quite high (Fig. 3). There are a number of factors that can contribute to this phenomenon, including time of infection, varieties, weather, and treatment. The point is, be sure this doesn’t happen to you. Scout AND have finished grain tested so you aren’t surprised at the elevator!

Wisconsin Winter Wheat Disease Update – June 6, 2018

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 Wisconsin Field Crops Pathology Team has been busy scouting and rating diseases of winter wheat this past week across the major wheat growing region of the state. To be honest, it has been pretty boring for our group. We have seen virtually no disease in uniform variety trials or in production fields. This is good news for farmers, for sure.

We have not yet confirmed any stripe rust infections in the state of Wisconsin, this season. Reports from farmers and consultants are also consistent with our observations. This is a considerable change from last season, when we found our first stripe rust pustules at the end of March. This early epidemic in 2017 resulted in some considerable yield loss from stripe rust on winter wheat. Definitely not the case this season. We have also seen extremely low levels of Septoria leaf blotch in the lower portions of the canopy on some varieties. Cool dry weather is preventing this disease from really moving up the canopy. No other foliar diseases have been confirmed on winter wheat this season.

As for the Fusarium head blight (FHB; scab) situation, risk as calculated by the Fusarium Risk Tool, has dissipated over the past week. Two weeks ago, risk of FHB had been estimated to be high on susceptible cultivars. However, cool dry weather has driven the risk to low levels across much of the major wheat production area of Wisconsin. Risk is high still along the Lake Michigan shore and up into Door County. Also elevated and high risk are estimated in Northwest Wisconsin on susceptible cultivars. The situation should be monitored closely in these areas on any crop heading into anthesis. Most of the wheat we have looked at across the southern, south-central, and north-eastern wheat production area of the state is through anthesis or will be by the end of the week. The FHB risk is forecast to be low through this period, in these areas. We will begin scouting for FHB damage in the next week or so, but we anticipate FHB to be mostly low in many areas, with some isolated pockets of higher levels.

It is important to continue scouting over the next couple of weeks. We are transitioning away form making fungicide spray decisions, but it is important to determine the level of FHB present in a particular field, so that proper harvest preparations can be made. We will continue to update you on what we find over the next couple of weeks. However, this is the lowest level of disease on winter wheat I have seen since I have been in Wisconsin. Scout, Scout, Scout!

Wisconsin Winter Wheat Disease Update – May 30, 2018

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

Warm weather last week, which continued into this week, has pushed the winter wheat crop in Wisconsin toward heading. Most varieties planted in the southern or south-central region of Wisconsin are heading, with full emergence and anthesis (flowering) beginning by the end of the week. We suspect that winter wheat in the northern and northeastern portions of the Wisconsin wheat belt to not be far behind.

Now is the time to consider your Fusarium head blight (FHB; scab) management strategy. Weather late last week had driven the FHB risk on the Fusarium Head Blight Prediction Center to a high level for susceptible varieties. Extremely hot and dry weather has forced the risk back to “low” today. However, 72 hour forecasts show risk increasing to medium in much of the wheat belt with high risk in isolated pockets on susceptible varieties (see figure). Rain today, with continued humidity and temperatures in the 80s F for the rest of the week, will keep risk elevated. Areas near the Lake Michigan shore will likely be at high risk.

A fungicide may be needed especially on susceptible cultivars to control FHB and reduce DON (vomitoxin) contamination. The fungicides Prosaro or Caramba have both performed well on FHB in Wisconsin. Timing of application of these products is critical. I would urge you to wait until anthesis has begun in your field before applying. We have observed poor control where application of these effective fungicides were made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed 4-5 days after the beginning of anthesis, compared to applications at the start of anthesis. Data from a fungicide efficacy trial to support this observation can be found by clicking here and scrolling down to pages 16 and 17. Also, remember that application of fungicides should be made no later than 6-7 days after the start of anthesis. After this time, fungicide efficacy on FHB and DON control is much reduced.

Get out there and SCOUT, SCOUT, SCOUT and monitor the FHB Prediction Center!

Wisconsin Winter Wheat Disease Update – May 24, 2018

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 heavy moisture we have received over the last week, combined with high temperatures in the low-to-mid 80s F this week have pushed winter wheat growth stages. We have seen rapid stem elongation with flag leaves emerging in some fields in the southern and south central regions of Wisconsin. We continue to find wheat with little foliar disease. However, we are entering a critical time to make our first important fungicide decision related to protecting emerging flag leaves from foliar disease. Continue to scout. Weather has been conducive for some foliar diseases. However, wheat continues to remain “clean” then hold your fungicide application until anthesis.

Given the heat this week, I suspect that heads will be emerging for some varieties in the southern region over the next week or so, with anthesis to closely follow. The decision to apply fungicide will be critical at this time. Considering the wet weather and warm temperatures the “pump is primed” for Fusarium head blight (FHB; scab). The Fusarium Head Blight Prediction Center currently has the FHB risk at medium to high in the south, south-central and eastern portions of the wheat belt (See Figure). This situation needs to be monitored closely over the next couple of weeks as fields enter the anthesis growth stage. The weather outlook appears to be very humid, wet, and warm, which will only increase the risk of FHB.

A fungicide may be needed especially on susceptible cultivars to control FHB and reduce DON (vomitoxin) contamination. The fungicides Prosaro or Caramba have both performed well on FHB in Wisconsin. Timing of application of these products is critical. I would urge you to wait until anthesis has begun in your field before applying. We have observed poor control where application of these effective fungicides were made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed 4-5 days after the beginning of anthesis, compared to applications at the start of anthesis. Data from a fungicide efficacy trial to support this observation can be found by clicking here and scrolling down to pages 16 and 17. Also, remember that application of fungicides should be made no later than 6-7 days after the start of anthesis. After this time, fungicide efficacy on FHB and DON control is much reduced.

Get out there and SCOUT, SCOUT, SCOUT and monitor the FHB Prediction Center!

Wisconsin Winter Wheat Disease Update – June 30, 2017

Stripe rust in a “striped pattern” on winter wheat leaves.

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

Brian Mueller, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin-Madison

The Wisconsin Field Crops Pathology team has nearly finished all of our assessments of wheat and wheat disease for the year in Wisconsin. Winter wheat is well on its way to maturing. The few spring wheat acres we have seen have mostly completed anthesis throughout much of the state, with just a few late-planted locations still completing anthesis.

Overall, the spring 2017 wheat season can be defined mostly by the widespread presence of stripe rust. We have been in fields where stripe rust has caused significant widespread damage on susceptible varieties that were not treated with fungicides. We have also observed fields that either had a resistant variety, received a fungicide application, or both. These fields appear to be doing quite well and the crop will yield well. Clearly areas where we suspect that there was overwintering of the stripe rust pathogen, saw the occurrence of the epidemic very early, resulting in quick spread of stripe rust this season. We have completed rating of stripe rust in the wheat variety trials in Wisconsin and these data will be published later this year in the variety performance report. I would encourage you to study these results carefully and choose varieties that performed well in your area and had low levels of stripe rust. This is the second year in a row that we have had a substantial stripe rust epidemic and choosing resistant varieties is a cheap method of stripe rust management.

We have also been looking for Fusarium head blight (FHB or scab) in commercial fields and variety trials. For a second year in a row, FHB incidence and severity is extremely low statewide. In many fields we struggle to find even one symptomatic head. Fusarium head blight incidence in the far southwest part of the state is nearly undetectable and approaches about 1% incidence in fields in the north-central and northeastern portions of the state. I expect that DON (vomitoxin) levels will be relatively low in finished grain in Wisconsin, this season. The low level os FHB in winter wheat this season is likely due to the unseasonably hot, dry weather we had in early June, which coincided with anthesis in many wheat fields. This type of weather is not conducive for the fungus and likely resulted in very few successful infection events.

Other diseases have been extremely hard to find. We have seen some fields with low levels of Septoria/Stagonospora, but in general these epidemics will not limit yield to a significant extent. Powdery mildew can be found infrequently on a few plants in some fields. In the southern portion of the state, we were able to find some leaf rust just this week. The arrival of leaf rust is likely too late to affect yield this season. We have not observed any stem rust in our scouting trips to commercial fields or in variety trials.