Wisconsin Winter Wheat Disease Update – May 31, 2023

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

Diseases of wheat in Wisconsin have basically been non-existent this season. Dry weather is leading to virtually no disease issue with the exception of one disease. Like 2021, powdery mildew is starting to show up on susceptible varieties. This one fungal disease likes to break the rules of cool and wet. Let’s discuss this disease further and then dig in a bit on what you should do for disease management as we move through the rest of the 2023 winter wheat season.

Figure 1. Signs and symptoms associated with powdery mildew on a wheat leaf.

So, what’s up with powdery mildew

Powdery mildew of winter wheat is caused by the fungus Blumeria graminis f. sp. tritici. The most notable sign of powdery mildew is the white, fluffy fungal growth that occurs on the surface of leaves (Fig. 1). Yellow spots may be present on the underside of the leaf. The white “tufts” might also have very small black pepper-like structures in them. Generally, the disease will start in the lower canopy, and if weather is favorable, will move up the canopy eventually reaching the flag leaf and even infecting heads on susceptible varieties.

The reason that powdery mildew has been an issue this year, despite the dry weather, is that it happens to like cool night-time conditions combined with high humidity and dew events. Warm days and cool nights often lead to dew and extended periods of leaf wetness (think semi-arid climates). This combined with temperatures less than 80 F, means the fungus can thrive on susceptible varieties where humidity has been high. Excessive rain events actually deter this particular fungus, as heavy rain events can wash spores from the leaf. So, it isn’t surprising that we are seeing powdery mildew right now given the weather we have had in parts of the state.

Should you spray fungicide for powdery mildew?

Most of the time I would say no. Often in Wisconsin, the weather begins to turn much warmer as we approach heading and the fungus will stop spreading and remain a novelty in the lower canopy. Remember, once daytime temperatures get above 80 F, the fungus will stop or slow in progression. The key in making the fungicide spray decision is to know the susceptibility of the variety you planted and watch the weather. If the weather remains conducive (temps below 80 F, no rain, but dew) and the variety is ranked susceptible, then spraying around flag leaf emergence might be warranted. You can consult the “Fungicide Efficacy for Control of Wheat Diseases” table for products rated with the best efficacy for powdery mildew. Note that most of the higher rated products are triazole compounds, or compounds with a triazole in their mix. No need to be fancy here, find something that fits your budget and has good efficacy. There should be ample choices.

Figure 2. FHB on some wheat heads. Note the bleached and reddened appearance of infected kernels.

I don’t care about powdery mildew, but what disease should I keep an eye on next?

Fusarium head blight (Fig. 2) has been a perennial problem for us in Wisconsin over the last few years. Not only have we seen significant damage and yield reductions due to the disease, but we have seen significant discounts at the elevator for levels of deoxynivalenol (DON or Vomitoxin) above 2 ppm. The one exception was 2021, which is sort of shaping up similar to 2023. However, it remains important to manage this disease actively here in Wisconsin.

Be sure you know the relative susceptibility of the varieties you have planted. We have excellent data showing significant reductions of FHB where we use a resistant variety and then layer a fungicide application on top. In 2019 we evaluated the susceptible variety, Hopewell, against the resistant variety, Harpoon. Figure 3 shows the FHB levels for the two varieties which were also subjected to a fungicide application. Clearly variety resistance works.

Figure 3. Fusarium head blight index (FHB Index) from a 2019 integrated management trial where the susceptible variety, Hopewell, and the resistant variety, Harpoon, were both treated with various fungicide programs or not treated with fungicide.

When it comes to fungicides for FHB, there are a few to choose from. These are Caramba, Prosaro, Miravis Ace, Prosaro Pro, and Sphaerex. Again the “Fungicide Efficacy for Control of Wheat Diseases” table shows the efficacy ratings of these products against FHB. Timing is everything when using a fungicide for FHB management. Be sure to time applications at the start of anthesis or within 5-7 days after the start. This is the ideal window of opportunity to control FHB and reduce DON levels in the finished grain. Spraying earlier than anthesis or later than about a week after the start of anthesis will result in lost efficacy, or no control of FHB. Also, these fungicides are effective against powdery mildew, so if that disease happens to be an issue for the variety you have chosen, a single application of fungicide at the anthesis timing should take care of both problems.

Should I spray for Fusarium head blight in 2023?

The answer to that question is a little complicated. However, there is a tool that can help with this decision. You can find the FHB prediction tool at http://www.wheatscab.psu.edu.This tool should be monitored frequently as your crop approaches anthesis and soon after. It can help you determine if your crop is at risk, based on the weather conditions. We are quickly approaching anthesis in the southern portion of Wisconsin. As of May 31, 2023, the risk for FHB in the whole state of Wisconsin is low, even on susceptible varieties. Again, dry weather leading up to this week has not been favorable for FHB. The 7-day forecast is also not looking conducive. Thus, the likelihood of a significant return on the fungicide investment is likely to be low this season. However, if you are risk adverse and would like to put an anthesis application of fungicide on, I would not be fancy with my choice. You might choose the cheapest product you can get ahold of, that is rated at least “G” on the fungicide efficacy table. This is not the season where you need to spend a lot of money on a fungicide, as the yield benefits are going to be lower due to the dry weather at heading. If you would like to study the performance of fungicide in wheat trials in Wisconsin, you can find trial data from my research going back 10 years by CLICKING HERE. Be sure to study multiple years and make sure a product was consistent in performance.

The ‘Take Home’ for wheat management over the next couple of weeks.

This can be cooked down to two main points. Here they are:

  • Don’t get too concerned about powdery mildew unless your variety is rated suscpetible
    1. If that is the case, then plan to apply a fungicide at anthesis for FHB (see below)
  • If you plan to apply an FHB fungicide application – especially on susceptible varieties
    1. Shoot for Anthesis or up to 5-days after the start of anthesis for any of the fungicides that are rated “G” in the fungicide efficacy table
    2. Can go slightly earlier (Feekes 10.5; Efficacy slightly reduced compared to typical timing) up to 5-days after the start of anthesis for Miravis Ace
    3. Watch the “Scab Alerts” – it isn’t perfect, but can help you make a decision (http://www.wheatscab.psu.edu)

Wisconsin Winter Wheat Disease Update – May 28, 2021

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

Figure 1. Fusarium head blight risk for susceptible winter wheat varieties for Wisconsin as of May 28, 2021.

Winter wheat in Southern and South-central Wisconsin is quickly approaching anthesis. By early next week the window of opportunity to apply fungicide for Fusarium head blight (FHB; scab) will be here. Currently the risk for FHB is variable and ranges from low to high depending on where you are in the state (Figure 1). Given the recent rain events and rising temperatures, I think the risk is there for FHB next week. This situation should be monitored closely and a timely fungicide application decision should be made. In my previous post, I talk about how to manage FHB.  There are essentially three options for products in Wisconsin for control of FHB. These include Prosaro, Caramba, and Miravis Ace. All also have efficacy against other foliar diseases too. Remember, your window of opportunity to spray for FHB ranges from the start of anthesis (flowering) to about 7 days after the start of anthesis.

Stripe rust still remains unidentified in the state. Confirmed reports of stripe rust are only as close as central Illinois (Figure 2). Continue to remain diligent in scouting for this disease. Remember that fungicides for control of FHB will also be efficacious for stripe rust. Thus, we should be able to “kill two birds with one stone” when spraying for FHB.

Figure 2. Confirmed stripe rust reports for the U.S. as of May 28, 2021.

Reports of powdery mildew continue to come in.  Remember that the FHB fungicide treatments will control this disease. So at this point, two applications of fungicide are not needed. A well-timed FHB-focused fungicide app should help slow powdery mildew.

Get out there and scout, scout, scout!

Managing Winter Wheat Diseases in Wisconsin During the 2021 Field Season

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

Up until this week diseases of winter wheat have been basically non-existent. Dry weather leading to a moderate drought in much of the state has meant that the environment has not been favorable for most wheat pathogens of concern for us in the upper Midwest. There is an exception to that rule, and we have observed one disease, and gotten reports of that disease this week. That disease is powdery mildew and does tend to follow a few different “rules” when it comes to fungal diseases. Let’s discuss this disease further and then dig in a bit on what you should do for disease management as we move through the rest of the 2021 winter wheat season.

So, what’s up with powdery mildew?

Figure 1. Signs and symptoms associated with powdery mildew on a wheat leaf.

Powdery mildew of winter wheat is caused by the fungus Blumeria graminis f. sp. tritici. The most notable sign of powdery mildew is the white, fluffy fungal growth that occurs on the surface of leaves (Fig. 1). Yellow spots may be present on the underside of the leaf. The white “tufts” might also have very small black pepper-like structures in them. Generally, the disease will start in the lower canopy, and if weather is favorable, will move up the canopy eventually reaching the flag leaf and even infecting heads on susceptible varieties.

The reason that powdery mildew has been an issue this year, despite the dry weather, is that it happens to like cool conditions combined with dew events. Warm days and cool nights often lead to dew and extended periods of leaf wetness (think semi-arid climates). This combined with temperatures less than 80 F, means the fungus can thrive on susceptible varieties. Excessive rain events actually deter this particular fungus, as heavy rain events can wash spores from the leaf. So, it isn’t surprising that we are seeing powdery mildew right now given the weather we have had.

Should you spray fungicide for powdery mildew?

Most of the time I would say no. Often in Wisconsin, the weather begins to turn much warmer as we approach heading and the fungus will stop spreading and remain a novelty in the lower canopy. Remember, once daytime temperatures get above 80 F, the fungus will stop or slow in progression. The key in making the fungicide spray decision is to know the susceptibility of the variety you planted and watch the weather. If the weather remains conducive (temps below 80 F, no rain, but dew) and the variety is ranked susceptible, then spraying around flag leaf emergence might be warranted. You can consult the “Fungicide Efficacy for Control of Wheat Diseases” table for products rated with the best efficacy for powdery mildew. Note that most of the higher rated products are triazole compounds, or compounds with a triazole in their mix. No need to be fancy here, find something that fits your budget and has good efficacy. There should be ample choices.

I don’t care about powdery mildew, but what disease should I keep an eye on next?

The last few seasons, two diseases have been our primary focus on winter wheat in Wisconsin. These diseases are stripe rust and Fusarium head blight (scab or FHB). In 2019 and 2020, only FHB was yield limiting. However, in 2016 and 2017, we dealt with both stripe rust and FHB in the same season. Obviously, this year could be different, but the stripe rust situation is starting to “heat up” a bit to our south. The “Wheat Ag Pest Monitor for Stripe Rust”  indicates that there are confirmed cases of stripe rust in central Illinois (Fig. 2). This situation needs to be watched carefully over the next 1-2 weeks in Wisconsin.

 

Figure 2. Confirmed stripe rust observations in the U.S. as of May 19, 2021.

 

We are rapidly approaching the first growth stage where the application of fungicide might be warranted if stripe rust is found in your locale or is nearby. Based on recent published research, in years where stripe rust was active at the emerging flag leaf growth stage (Feekes 8), we obtained excellent control of stripe rust and a positive return on investment where we sprayed fungicide at this growth stage with a second application of fungicide for FHB control around anthesis.

Currently there is no stripe rust confirmed in Wisconsin but given the rainy weather recently and the positive confirmations in Illinois, this situation should be closely monitored, and a fungicide might be warranted on susceptible varieties if stripe rust is found prior to heading.

If you decide you need to apply a fungicide, there are many choices with decent efficacy against stripe rust. Again, consult the “Fungicide Efficacy for Control of Wheat Diseases” table for the best ratings for the disease. Find a product that is efficacious and fits your farm budget.

So, what should I do about Fusarium head blight?

Figure 3. Fusarium head blight of winter wheat

Fusarium head blight (Fig. 3) has been a perennial problem for us in Wisconsin over the last 5 years. Not only have we seen significant damage and yield reductions due to the disease, but we have seen significant discounts at the elevator for levels of deoxynivalenol (DON or Vomitoxin) above 2 ppm. It is important to manage this disease actively here in Wisconsin.

Be sure you know the relative susceptibility of the varieties you have planted. We have excellent data showing significant reductions of FHB where we use a resistant variety and then layer a fungicide application on top. In 2019 we evaluated the susceptible variety, Hopewell, against the resistant variety, Harpoon. Figure 4 shows the FHB levels for the two varieties which were also subjected to a fungicide application. Clearly variety resistance works.

When it comes to fungicides for FHB, there are really just three products to choose from. These are Caramba, Prosaro, and Miravis Ace. Again the “Fungicide Efficacy for Control of Wheat Diseases” table shows the efficacy ratings of these products against FHB. Timing is everything when using a fungicide for FHB management. Be sure to time applications at the start of anthesis or within 5-7 days after the start. This is the ideal window of opportunity to control FHB and reduce DON levels in the finished grain. Spraying earlier than anthesis or later than about a week after the start of anthesis will result in lost efficacy, or no control of FHB. Also, these fungicides are effective against stripe rust, so if that disease happens to move in later, a single application of fungicide at the anthesis timing should take care of both problems.

 

Figure 4. Fusarium head blight index (FHB Index) from a 2019 integrated management trial where the susceptible variety, Hopewell, and the resistant variety, Harpoon, were both treated with various fungicide programs or not treated with fungicide.

 

There is a disease prediction tool for FHB of wheat. You can find that tool at http://www.wheatscab.psu.edu.This tool should be monitored frequently as your crop approaches anthesis and soon after. It can help you determine if your crop is at risk, based on the weather conditions. While most wheat as of May 19, 2021 is not near heading yet in Wisconsin, you can see in figure 5 that for susceptible FHB varieties, the risk is currently low. Again, dry weather leading up to this week has not been favorable for FHB.

 

Figure 5. Fusarium head blight risk as of May 19, 2021 in the U.S.

 

The ‘Take Home’ for wheat management over the next few weeks.

This can be cooked down to two main points. Here they are:

  • In some years applying fungicides for stripe rust on susceptible cultivars around Feekes 8 will be needed. Make this decision based on the following:
    1. The known susceptibility of the variety
    2. Local presence of strip rust and/or confirmed reports nearby
    3. Favorable weather (frequent rains and temperatures less than 80 F)
  • Plan to apply an FHB fungicide application – especially on susceptible varieties
    1. Shoot for Anthesis or up to 5-days after the start of anthesis for Prosaro and Caramba fungicides
    2. Can go slightly earlier (Feekes 10.5; Efficacy slightly reduced compared to typical timing) up to 5-days after the start of anthesis for Miravis Ace
    3. Watch the “Scab Alerts” – it isn’t perfect, but can help you make a decision (http://www.wheatscab.psu.edu)

 

Wisconsin Winter Wheat Disease Update – June 2, 2020

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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 Risk Tool prediction for FHB-susceptible varieties of winter wheat in Wisconsin on June 2, 2020.

Winter wheat in Wisconsin is moving through growth stages very rapidly over the past week due to ample moisture and heat. I have visited several fields this week with heads emerging or almost completely emerged. Anthesis (flowering) will begin in many winter wheat fields this week, if it hasn’t already started.

With the start of anthesis comes the critical time to consider a fungicide application for Fusarium head blight (FHB or scab). The Fusarium Risk Tool is showing very favorable conditions for the major wheat producing areas of Wisconsin, for susceptible varieties (Fig. 1). Risk is also medium-to-high in these zones for moderately susceptible varieties. Given the heat and high humidity with the multiple chances of rain predicted, a fungicide application may be warranted at this time in your winter wheat fields, especially if you have susceptible varieties.

Remember that the best time to apply a fungicide for FHB control is at the start of anthesis, up to 7 days after the start of anthesis. In Wisconsin, our research has demonstrated that we can significantly reduce the levels of deoxynivalenol (DON or vomitoxin) in finished grain if we wait until 5 days after the start of anthesis to apply our FHB fungicide. This is due to the fact that we often have uneven head emergence in our fields and delaying applications a few days after the start of anthesis can let these heads (or those on secondary tillers) “catch up.”

Fungicides considered most consistent in efficacy in University research include Prosaro®, Caramba®, and Miravis Ace®. Efficacy ratings for these and other products can be found on the Crop Protection Network’s Fungicide Efficacy for Control of Wheat Diseases fact sheet. Results from fungicide efficacy trials from the Badger Crop Docs, can be found BY CLICKING HERE. Research trials from 2019 that include the newest fungicide, Miravis Ace®, can be found BY CLICKING HERE and scrolling down to the last several pages. Remember, that the goal is to reduce damage by FHB and reduce DON levels as far below 2ppm as possible. The ideal method to do this includes an integrated approach of using resistant varieties and well-timed fungicide applications.

Figure 2. Stripe rust occurrence for a portion of the U.S. as of June 2, 2020

In our travels over the past week we also found stripe rust at very low levels in the Wisconsin Winter Wheat Variety trial located in Chilton, WI (Calumet Co.). We have documented this on the stripe rust monitor (Fig. 2). This was at low severity on flag leaves of known susceptible and moderately susceptible varieties of winter wheat. We have not observed stripe rust in the other variety trials in the state, or in other fields we have visited at this point. I believe that the high heat will keep stripe rust moving slowly. In addition, fungicide applications that will be applied for FHB control will also be effective in reducing the severity of stripe rust.

Now is the time to get out and SCOUT, SCOUT, SCOUT and make those educated fungicide spraying decisions!

Wisconsin Winter Wheat Disease Update – May 27, 2020

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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 Risk Tool prediction for FHB-susceptible varieties of winter wheat in Wisconsin on May 27, 2020.

Winter wheat in Wisconsin has responded to above average temperatures and rainfall, rapidly advancing through growth stages. In just a week or so, mainstems have rapidly elongated. In some varieties in southern and south-central Wisconsin, flag leaves are fully out. While now is a good time to consider a fungicide application, foliar disease has been non-existent in fields we have been in. We are monitoring the stripe rust situation carefully, and while it is active in states to our south, we have not observed any in fields we have scouted. The above average heat will also keep stripe rust moving slowly, especially in varieties with moderate resistance. So for now, I think we can hold off on fungicide. With margins being tight, I think it is wise to keep our fungicide application for Fusarium head blight (FHB or scab). Fungicides directed toward FHB are also effective against stripe rust, should it move in later in the season. Continue to scout fields between now and head emergence to catch any foliar diseases that might emerge.

Speaking of FHB, conditions have been VERY conducive for this disease in Wisconsin over the past week. The Fusarium Risk Tool is showing very favorable conditions for the entire state of Wisconsin for susceptible varieties (Fig. 1) and favorable conditions in the southern portion of the state for even moderately resistant varieties. This situation needs to be monitored over the next few days as heads start to emerge and anthesis (flowering) begins. Humid/wet and warm conditions will keep risk of FHB high as anthesis begins. We have also had several years of significant FHB and Gibberella ear rot in corn, meaning we have ample inoculum sources locally to initiate FHB epidemics. Farmers with winter wheat should be prepared to make a fungicide application if these conditions persist, especially those with wheat varieties rated as susceptible to FHB.

Remember that the best time to apply a fungicide for FHB control is at the start of anthesis, up to 7 days after the start of anthesis. In Wisconsin, our research has demonstrated that we can significantly reduce the levels of deoxynivalenol (DON or vomitoxin) in finished grain if we wait until 5 days after the start of anthesis to apply our FHB fungicide. This is due to the fact that we often have uneven head emergence in our fields and delaying applications a few days after the start of anthesis can let these heads (or those on secondary tillers) “catch up.”

Fungicides considered most consistent in efficacy in University research include Prosaro®, Caramba®, and Miravis Ace®. Efficacy ratings for these and other products can be found on the Crop Protection Network’s Fungicide Efficacy for Control of Wheat Diseases fact sheet. Results from fungicide efficacy trials from the Badger Crop Docs, can be found by CLICKING HERE. Research trials from 2019 that include the newest fungicide, Miravis Ace®, can be found by CLICKING HERE and scrolling down to the last several pages. Remember, that the goal is to reduce damage by FHB and reduce DON levels as far below 2ppm as possible. The ideal method to do this includes an integrated approach of using resistant varieties and well-timed fungicide applications. Continue to monitor the wheat disease situation closely and get out and Scout, Scout, Scout!

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

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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

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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

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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

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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

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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.