Fusarium Head Blight in Wisconsin Winter Wheat: A Guide for Harvest Preparation

/in , , , /by

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

Shawn Conley, Extension Soybean and Small Grains Agronomist, Department of Plant and Agroecosystem Sciences, University of Wisconsin-Madison

This season, we’ve observed moderate to high levels of Fusarium head blight (FHB), also known as scab, in some Wisconsin winter wheat fields. The incidence and severity have varied based on location, the susceptibility of the wheat variety, and whether a fungicide was applied at or shortly after anthesis.

FHB has been more prevalent in the southern and south-central wheat-growing areas of the state. However, it can also be found in other areas, depending on the susceptibility of the wheat varieties grown. As you prepare for harvest, it’s crucial to scout your maturing wheat crop and estimate the potential damage from FHB.

FHB can cause direct yield loss, and the fungus that causes this disease can also produce deoxynivalenol (DON), also known as vomitoxin.

Identifying FHB

Figure 1. Fusarium head blight of winter wheat

In non-mature winter wheat or spring wheat fields, diseased spikelets on an infected grain head die and bleach prematurely, while healthy spikelets on the same head retain their normal green color (Fig. 1). 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. Infected kernels often 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 FHB Identification is Important

FHB identification is important because it not only reduces yield but also decreases the quality and feeding value of grain. The FHB fungus may produce mycotoxins, including DON or vomitoxin, which can adversely affect livestock and human health when ingested.

The U.S. Food and Drug Administration has set maximum allowable levels of DON in feed for various animal systems. For beef and feedlot cattle and poultry, the limit is less than 10 ppm; for swine and all other animals, it’s less than 5 ppm. However, many professional animal nutritionists agree that in ruminating cattle, the level of DON in the total ration should be below 1 ppm.

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.

Lodged Wheat and DON

We’ve noted many fields with high levels of lodging in Wisconsin this season. Research has shown that DON levels are significantly higher in lodged wheat compared to standing wheat. The longer wheat is lodged, the more DON accumulates. If you suspect that DON is a concern in your field and there is significant lodging, care should be taken during harvest to test grain for DON.

Preparing for Wheat Harvest

  1. Adjust combine settings to blow out lighter seeds and chaff. Research has shown that adjusting a combine’s fan speed from 1,375 to 1,475 rpms (100 rpms above standard configuration) and shutter opening to 90 mm (3.5 inches; 20 mm wider than the standard configuration) resulted in the lowest discounts at the elevator due to low test weight, percentage of damaged kernels, and level of the mycotoxin deoxynivalenol (DON; vomitoxin) present in the harvested grain. This strategy should be used only for fields expected to have high levels of scab, as harvested yield can also be reduced in field with normal kernels due to the higher air flow.
  2. Take special care when harvesting fields that are lodged. Remember that higher levels of DON are likely in fields with lodged wheat. Be sure to test grain so you know what the DON concentration is before taking the crop to the elevator.
  3. Know your elevator’s inspection and dockage procedure and discount schedule (each elevator can have a different procedure and discount rate).
  4. Scabby kernels do 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.
  5. 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. If in doubt, have the straw tested for DON levels.
  6. 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.
  7. Do not store grain from fields with high levels of scab. DON and other mycotoxins can continue to increase in stored grain.
  8. 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.

For more information on Fusarium head blight research, 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. Nakajima, T., Yoshida, M, and Tomimura, K. 2008. Effect of lodging on the level of mycotoxins in wheat, barley, and rice infected with Fusarium graminiearum species complex. J. Gen. Plant Pathol. 74:289-295.
  4. 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 – May 24, 2024

/in , , , /by

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

Shawn Conley, Extension Soybean and Small Grains Agronomist, Department of Plant and Agroecosystem Sciences, University of Wisconsin-Madison

Figure 1. Stripe rust on a flag leaf of winter wheat.

Winter wheat in Wisconsin continues to move through growth stage ahead of average. This week I have seen many wheat heads emerged and anthers out. We have also confirmed stripe rust (Fig. 1) in Columbia and Dodge Counties. Now is the time to make a decision on a fungicide application in winter wheat.

In my previous post I mentioned the importance of balancing both stripe rust and Fusarium head blight (FHB) as we moved into the next several weeks. Now that anthers are emerging on wheat heads, the time is right to get a fungicide application out to control FHB. These fungicides will also control stripe rust. You can find an excellent list of fungicides that will control both FHB and stripe rust HERE.

Given the current stripe rust movement into the state (Fig. 2) and potential risk for FHB to increase (Fig. 3), I think a fungicide should be strongly considered to protect yield in winter wheat this season. I realize that the Fusarium risk tool is still showing much of Wisconsin in a low risk of FHB. However, with stripe rust moving in at this point and the rainy weather, choosing an FHB fungicide to apply now at anthesis is a wise decision in my opinion. The optimal timing of application of fungicide at this point in the season is the start of anthesis (50% of heads showing at least one anther) to 7 days after the start of anthesis. This will maximize control of FHB while also providing control of stripe rust and the mycotoxin deoxynivalenol (DON).

Figure 2. U.S. counties confirmed to have stripe rust on wheat – May 24, 2024.

 

Figure 3. Risk of Fusarium head blight based on the Fusarium risk tool – May 24, 2024.

As always, be sure to get out in the field and scout, scout, scout! Making an informed decision is key to success!

Wisconsin Winter Wheat Disease Update – May 16, 2024

/in , , , /by

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

Shawn Conley, Extension Soybean and Small Grains Agronomist, Department of Plant and Agroecosystem Sciences, University of Wisconsin-Madison

Winter wheat in Wisconsin continues to move through growth stages at record pace. We are about 10-14 days ahead on growth stages compared to this time in most years in Wisconsin. The warm spring and timely rain has pushed wheat very quickly.

As I mentioned last week, we continue to monitor the stripe rust situation. This week brings us a confirmed stripe rust positive in Tippecanoe Co. Indiana (Fig. 1). As I mentioned in my previous article, the likelihood is high that we will see stripe rust in Wisconsin this season. We have continued to scout for this disease and visited several variety and research location this week in southern Wisconsin. We have not found stripe rust yet. This doesn’t mean that it isn’t here. I still encourage you to scout and let us know if you find it or get it confirmed by our Plant Disease Diagnostic Clinic.

With the rapid growth stage changes happening, we are quickly approaching the time in the season that we need to be aware of risk and in-season management decisions for Fusarium head blight. Fusarium head blight (FHB) has typically been a more frequently occurring issue in Wisconsin. However, in recent years, our spring seasons have been exceptionally hot and dry leading to little disease. However, this season is different with moderate temperatures and adequate precipitation to make FHB an issue. Not only is the disease yield limiting, but the fungus that causes FHB can also produce the mycotoxin called deoxynivalenol (DON or vomitoxin). DON contamination above 2 ppm in finished grain can often lead to discounts at the elevator or outright rejection. Thus, this disease is worth managing.

Fortunately, we have some excellent in-season management options for FHB. 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. Varietal resistance works!

When it comes to fungicides for FHB, there are really just five products to choose from that are rated as “Good” on the “Fungicide Efficacy for Control of Wheat Diseases” table. 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. If you need help with growth staging, be sure to check out the “Visual Guide to Winter Wheat Development and Growth Staging.” Also, the fungicides rated “G” for FHB in the fungicide efficacy table are effective against stripe rust, so if that disease happens to move in now or later, a single application of fungicide at the anthesis timing should take care of both problems.

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. Risk as of May 16, 2024 for FHB-suscpetible winter wheat varieties is currently estimated to be low (Fig. 2). However, given the 7-day forecast of rain and warm temperatures, I would suspect this to change to be more favorable for FHB risk in the coming 7-10 days. If you haven’t applied a fungicide yet this season, I would urge you to consider one, well-timed application targeting FHB this season.

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

  1. Plan to apply an FHB fungicide application – especially on susceptible varieties
  2. Shoot for Anthesis or up to 5-days after the start of anthesis for the fungicides rated “G” for FHB in this table.
  3. All of the available fungicides rated for FHB also are effective against stripe rust. Thus, one fungicide can manage both problems!
  4. You 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 to manage FHB.
  5. 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 31, 2023

/in , , , /by

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 – June 1, 2022

/in , , /by

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

In Wisconsin, wheat diseases have been nearly non-existent up to this point. Cool weather has generally kept wheat disease at low levels. However, increase frequency of rain events and moderate temperatures over the next 7-10 days will likely increase disease risk, especially Fusarium head blight (FHB or Scab). 

Fusarium head blight risk for susceptible winter wheat varieties for June 1, 2022.

We are entering the window for fungicide applications for FHB here in Wisconsin. Currently the Fusarium Head Blight Risk tool is predicting more areas of moderate to high risk in Wisconsin for FHB than it did a week ago (Fig. 1). If highly susceptible wheat varieties were planted in Wisconsin, the current risk is high across most of the state. Rainy conditions in the next seven days will likely push this risk higher. Now is the time to consider a fungicide application to manage FHB in Winter wheat in the state.

In winter wheat in Wisconsin, research has demonstrated that the best time to apply fungicides is between the start of anthesis (first anthers out) to 7 days after the start of anthesis. This same research has demonstrated that waiting to apply fungicides 5 days after the start of anthesis, optimizes deoxynivalenol (DON or vomitoxin) reductions in finished wheat. This is due to the fact that head emergence in Wisconsin can be very uneven. Waiting 5 days after the start of anthesis may help with optimizing application timing to maximize heads flowering and receiving fungicide protection. Fungicide choice is also critical, with Prosaro, Caramba, and Miravis Ace providing the most consistent control of Fusarium head blight and reduction of DON in trials in Wisconsin. Fungicides containing strobilurin fungicides should be avoided after the boot stage of wheat as these products can increase DON levels in finished grain. Fungicide efficacy information from Wisconsin can be found at https://badgercropdoc.com/research-summaries/. National ratings for fungicide efficacy of small grains can be found HERE. Additional thoughts on using fungicide on wheat can be found in this Bumper Crops Video.

We also know that in Wisconsin, that a fungicide application targeted to manage FHB will pay for itself almost every time. You can find published research information on the probability of a return on fungicide investment by clicking HERE. Be sure to focus on comparing the “current” level of treatment to the “mid-level” of treatment in the publication. The only difference between these two treatment plans was the application of fungicide at Feekes 10.5.1 to manage FHB. The “mid-level” plan returned on average more than $120 per acre above the “current” management plan in our trials.

Keep scouting!

 

Wisconsin Winter Wheat Disease Update – May 24, 2022

/in , , /by

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

Figure 1. Fusarium Head Blight Risk Map – May 24, 2022.

Winter Wheat is Wisconsin is in the “boot “or heading in the southern part of the state. Currently the Fusarium Risk Assessment Map is showing low risk for Fusarium head blight development (Fig 1). Rain is forecast for the next several days, thus, the risk is likely to climb as we approach wheat heading and flowering. Wheat farmers and consultants should pay attention to weather closely over the next several weeks as the decision to apply fungicide will need to be made during this time.

In winter wheat in Wisconsin, research has demonstrated that the best time to apply fungicides is between the start of anthesis (first anthers out) to 7 days after the start of anthesis. This same research has demonstrated that waiting to apply fungicides 5 days after the start of anthesis, optimizes deoxynivalenol (DON or vomitoxin) reductions in finished wheat. This is likely since head emergence in Wisconsin can be very uneven. Waiting 5 days after the start of anthesis may help with optimizing application timing to maximize heads flowering and receiving fungicide protection. Fungicide choice is also critical, with Prosaro, Caramba, and Miravis Ace providing the most consistent control of Fusarium head blight and reduction of DON in trials in Wisconsin. Fungicides containing strobilurin fungicides should be avoided after the boot stage of wheat as these products can increase DON levels in finished grain. Fungicide efficacy information from Wisconsin can be found at https://badgercropdoc.com/research-summaries/. National ratings for fungicide efficacy of small grains can be found HERE. Additional thoughts on using fungicide on wheat can be found in this Bumper Crops Video.

Wisconsin Winter Wheat Disease Update – May 28, 2021

/in , , , /by

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

/in , , , , /by

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 23, 2020

/in , , , , , /by

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 2, 2020

/in , , , , , /by

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!