Fusarium Head Blight and Wisconsin Wheat Harvest in 2016

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. Fusarium head blight on a wheat head

Figure 1. Fusarium head blight on a wheat head

Fusarium head blight (FHB) or scab has been relatively low in most Wisconsin winter wheat fields this season. Occasionally we have run across a field with somewhat higher levels of FHB; however, compared to the 2015 crop, we suspect that the 2016 winter wheat crop should have much less FHB. With that said, it is still 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.

What does scab look like? Diseased spikelets on an infected grain head die and bleach prematurely (Fig. 1).  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 beginning to mature. As maturity progresses over the next couple of weeks, 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 (Fig. 2). However, when the finished grain was tested for DON, significant levels were identified for all treatments (Fig. 3). 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. For more information on Fusarium head blight click here.

References

Cowger, C., and Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology 103:460-471.

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 16

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

Brian D. Mueller, Graduate Research Assistant, University of Wisconsin-Madison

Figure 1. Stripe rust spores on a wheat leaf, being collected for research.

Figure 1. Stripe rust spores on a wheat leaf, being collected for research.

The University of Wisconsin Field Crops Pathology team has completed leaf disease ratings at all Wisconsin winter wheat variety trials this week. We will begin rating for Fusarium head blight (FHB) damage in these same trials next week. We have also scouted wheat in production fields in various areas. Most wheat has completed anthesis and is filling grain. No FHB has been observed up to this point. However, stripe rust is pretty serious in most locations we have been (Figure 1). On susceptible varieties that haven’t been sprayed with a fungicide, we have observed 100% incidence with average severity on flag leaves ranging between 30 and 90%! We even have our token “Yellow Jeans” picture to demonstrate how severe stripe rust is in some fields (Figure 2). While there are many cases of severe stripe rust, we have observed some varieties to be very resistant. Little or no rust observed (Figure 3). I think there will be a wide range in yields of winter wheat this year in Wisconsin, based on stripe rust severity. Those who did not spray fungicide and have susceptibility will see significant yield losses and reduced test weight.

Figure 2. Stripe rust spore on denim jeans

Figure 2. Stripe rust spore on denim jeans

We have seen very few other foliar diseases on wheat during our travels. Leaf blotch diseases are present in some fields in the lower canopy, but in many cases, stripe rust is out-competing those diseases. We found powdery mildew in one isolated location in one field we have been in. We suspect that we will find some FHB over the next several weeks as portions of the state had favorable weather for the FHB fungus during anthesis. We will continue to monitor this situation and alert you to what we find.

Figure 3. A stripe rust susceptible winter wheat variety on the left and a resistant winter wheat variety on the right. Note the yellow leaves on the variety on the left.

Figure 3. A stripe rust susceptible winter wheat variety on the left and a resistant winter wheat variety on the right. Note the yellow leaves on the variety on the left.

Finally, I want to note that fungicide applications should not be made after the anthesis period. Most fungicide will no longer be effective on these diseases once established. Also, the pre-harvest intervals on these products will not allow application after the anthesis period.

Wisconsin Winter Wheat Disease Update – June 1

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

Brian D. Mueller, Graduate Research Assistant, University of Wisconsin-Madison

Figure 1. FHB Advisor June 1. 2016

Figure 1. FHB Advisor June 1. 2016

Despite the warm and rainy pattern that much of Wisconsin has been subjected to over the last week or so, the wheat FHB (scab) advisor  is predicting low risk of FHB over much of the state (Fig. 1). Just a narrow band of moderate to high risk exists very close to the Lake Michigan shore. Extending the advisor out 72 hours increases risk for FHB slightly for susceptible cultivars, but leaves the majority of the state still at low risk.

In addition to FHB risk, there is a relatively high incidence of stripe rust in many fields that we have scouted. The Wisconsin Field Crops Pathology Crew scouted Winter Wheat Variety trials and commercial fields near Chilton and Fond du Lac on May 27th. At both locations, wheat ranged from boot stage to heading. Anthesis will occur sometime this week or is occurring as we speak in many of the varieties.

The primary disease at the Fond du Lac location was stripe rust. Incidence (less than 10% across varieties) and severity (less than 5% on F1 or F2 leaves) was generally low in most varieties. One variety in the small plot variety trial had stripe rust present on very old tillers. In fact, stripe rust had been active for a while as telia (pathogen structure) were forming. I suspect that stripe rust may have over-wintered on this variety at Fond du Lac considering our mild winter.

At the Chilton location, stripe rust incidence was much higher (25-30%) however, severity was generally low (less than 5% on F1 leaves). However, there were several hot spots of stripe rust present in the variety trial and also commercial wheat surrounding the trial. Growers will need to watch this situation carefully. I fear that stripe rust will be increasing dramatically this week with our rainy and humid weather.

If a fungicide has not been applied yet, stripe rust is present, and anthesis has begun this week, a fungicide should be considered to control FHB and stripe rust together. The fungicides Prosaro or Caramba have both performed well on FHB in Wisconsin and are rated “Excellent” for stripe rust. 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 of FHB where application of these effective fungicides was 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. 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 is much reduced.

 

Wisconsin Winter Wheat Disease Update – May 24

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

Brian D. Mueller, Graduate Research Assistant, University of Wisconsin-Madison

Figure 1. Stripe rust in a "striped pattern" on winter wheat leaves.

Figure 1. Stripe rust in a “striped pattern” on winter wheat leaves.

The Wisconsin Field Crops Pathology Crew scouted winter wheat near Sharon, Wisconsin and Arlington Wisconsin yesterday. Wheat in these locations ranges from emerging flag leaf (Feekes 8) to boot stage (Feekes 10). Stripe rust (Figure 1) is increasing in incidence in the Sharon location while the overall severity (area of leaf covered by yellow spore-producing pustules) remains low. At the Arlington location, susceptible varieties in the uniform variety trial have high incidence and high severity with damage already reaching flag leaves. Wheat in surrounding fields is also beginning to show higher levels of stripe rust incidence. As previously mentioned in my May 11 post, stripe rust can be very yield limiting when it advances to the flag leaves before head emergence. Humid conditions and rainy weather will provide conditions favorable for stripe rust increase over the next week. Now is the time to scout winter wheat fields in the state and determine the incidence and severity of stripe rust in the lower canopy. By scouting the lower canopy, you can get an idea of how much risk there will be for stripe rust moving up to the flag leaf. Fungicides will be most effective when applied to wheat before stripe rust advances to the flag leaf. While scouting also note the growth stage of the wheat crop. This will be helpful in making fungicide application decisions.

To add fuel to the fire, we also need to start thinking about Fusarium head blight (FHB) or scab. Within a week or so, there will likely be fully emerged heads with anthers present on some wheat varieties in the southern and south-central region of Wisconsin. This will be a critical time to make a decision about fungicide application to control FHB. Currently, the Wheat Scab Advisor is showing little risk for FHB (Figure 2). I would urge you to pay attention to the weather over the next week. We are about to enter a warm rainy period, which will be conducive for the FHB fungus, should heads emerge and anthesis begin during this time. The Wheat Scab Advisor will likely change quickly during this period. 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 is much reduced.

So now if you are still reading this, you are probably asking yourself “Well Damon, when should I spray fungicide now that I have two diseases to worry about and wheat is only worth $4/bu?”  My advice here will involve some leg work. I think folks need to see how much stripe rust is present this week and what growth stage the crop is at. If there is little rust present and the crop will be heading and going through anthesis in the next week or so, I would say to wait and target your fungicide application for FHB control. Both Prosaro and Caramba are rated “Excellent” in the University Small Grains Fungicide Efficacy Table.  Therefore, if you wait to spray, you are still applying a product that can protect flag leaves should stripe rust move in later. Also consider the level of resistance to stripe rust in your wheat variety. If the variety has a decent level of resistance, then the rate of spread of stripe rust up the canopy will be slow relative to susceptible varieties.

If the crop is only at the emerging flag leaf stage and you find active stripe rust in the crop, I would not wait to spray at anthesis. This could result in significant levels of stripe rust on flag leaves on susceptible or moderately susceptible varieties considering the conducive weather pattern that is forecast for Wisconsin. A strobilurin fungicide such as Headline or Aproach might be useful as a preventative application for stripe rust and these products are in a different class as Prosaro or Caramba. You should be aware that solo strobilurin fungicides do not perform well on stripe rust once the disease is established. A triazole or mixed-mode-of-action fungicide might be needed in this case, but be aware that could limit your use of Prosaro or Caramba for FHB management later in the season. Consult the fungicide labels carefully.

We have also had a couple reports of low levels of powdery mildew in a handful of fields and Septoria leaf blotch continues to cook along in the lower canopy in most fields. Stay diligent with scouting over the next couple of weeks and keep an eye on the weather. Hopefully we get enough rain to keep the crop moving along nicely and not enough to make disease worse. SCOUT, SCOUT, SCOUT!!

Results of the 2015 Wisconsin Winter Wheat Foliar Fungicide Trial

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

Fusarium head blight (scab) on a wheat head.

Fusarium head blight (scab) on a wheat head.

As we head into the 2015/16 Wisconsin winter wheat field season, I have received a lot of questions on Fusarium head blight (scab) management due to the heavy pressure from that disease in the 2014 and 2015 wheat crops. Along with those questions, always come inquiries about fungicide programs, specifically fungicide timing and fungicide products effective for controlling the disease. We have already addressed timing of application in this article: Start Managing for Fusarium Head Blight Now Before You Plant the 2015/16 Crop. But what about efficacy of products and fungicide programs? Previous results from 2013 and 2014 Wisconsin Winter Wheat Fungicide evaluations can be found by CLICKING HERE. In addition, you will find the 2015 fungicide evaluation results below.

The 2015 trial was established at the Arlington Agricultural Research Station located in Arlington, WI. The soft red winter wheat cultivar ‘Kaskaskia’ was chosen for this study. Wheat was planted on 24 Sep 2014. Treatments consisted of a non-treated control and 9 fungicide treatments. All fungicide treatments contained the non-ionic surfactant Induce 90% SL at 0.125% v/v. Fungicides were applied using a CO2 pressurized backpack sprayer calibrated to deliver 20 GPA. Fungicides were used to target general wheat disease in the area. Fungicides were applied either just before jointing (Feekes 5), at emerging flag leaf (Feekes 8), at anthesis (Feekes 10.5.1), or using two sprays with the first occurring just prior to jointing (8 May) or at emerging flag leaf (21 May) and the second spray being applied at anthesis (3 Jun). Natural sources of pathogen inoculum were relied upon for disease and plots were also inoculated with Fusarium graminearum (the head blight pathogen). Fusarium head blight was the primary disease in the trial and was evaluated by estimating average incidence in each plot. Level of deoxynivalenol (DON) will also be evaluated but results are not yet in.

Weather in spring 2015 was cool and rainy before transitioning to warmer and wet near wheat head emergence. Leaf disease incidence and severity was low in this trial. No powdery mildew was observed. Visible levels of Fusarium head blight were moderate in the non-treated control (see table below). All plots that received fungicide had significantly less Fusarium head blight than the non-treated control. Plots that received Prosaro or Caramba fungicide at the Feekes 10.5.1 application timing typically had lower levels of disease. Plots where fungicide was applied at Feekes 8 only typically had higher levels of Fusarium head blight compared to plots that received an application at Feekes 10.5.1. Plots with the lowest levels of Fusarium head blight receive either Quilt Xcel @ 10.5 fl oz/a or Stratego YLD @ 5.0 fl oz/a at Feekes 8 followed by Prosaro @ 6.5 fl oz/a at Feekes 10.5.1. Although, yield was highest in plots that received Stratego YLD @2.0 fl oz/a at Feekes 5 followed by Prosaro @ 6.5 fl oz/a applied at Feekes 10.5.1. Application of fungicide at the Feekes 10.5.1 timing reduced visible disease and often improved yield at this research location in 2015. Phytotoxicity was not observed for any treatment.

2015 Wheat Fungicide Table

Fusarium Head Blight a Significant Issue in Wisconsin in 2015

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: Symptoms of Fusarium head blight (scab) on a wheat head.

Figure 1: Symptoms of Fusarium head blight (scab) on a wheat head.

The 2015 growing season has been fairly challenging for managing winter wheat diseases. Many fields we have observed have some level of disease. Fusarium head blight (FHB or scab) is the primary disease observed in all locations from the southern portion of the state on up through Fond du Lac. In locations near Janesville, some varieties of winter wheat not sprayed with a fungicide have FHB incidence and severity levels close to 50%. Significant yield loss and quality issues, including high levels of deoxynivalenol (also known as DON or vomitoxin) will be a problem as farmers being to harvest grain in a couple of weeks. Fields should be assessed now for damage by FHB to understand how much DON might be expected in grain at harvest.

What does scab look like? Diseased spikelets on an infected grain head die and bleach prematurely (Fig. 1).  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 beginning to mature. As maturity progresses over the next couple of weeks, 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.
  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. For more information on Fusarium head blight click here.

Other Wheat Diseases in Wisconsin

Rust has also been an issue on winter wheat this season. Both stripe and leaf rust were observed at high levels near Arlington Wisconsin recently. Near Janesville, rust was observed to be more intermittent in occurrence. Stripe rust was present, however, incidence and severity of leaf rust was a bit higher on some varieties. Stagnospora/Septoria leaf blotch can be found in most locations. However, the disease has been present mostly in the lower canopy and has not made its way to the flag leaf. Powdery mildew has been nearly non-existent for the third year in a row in the state.

References

Cowger, C., and Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology 103:460-471.

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 10

Figure 1. FHB prediction for June 10 for 'very susceptible' winter wheat varieties.

Figure 1. FHB prediction for June 10 for ‘very susceptible’ winter wheat varieties.

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

Winter wheat in much of southern and central Wisconsin is now in active anthesis or past anthesis. Spraying for Fusarium head blight (FHB) is not recommended once wheat has progressed past 7 days after anthesis. Wheat from the east central to northeast is likely approaching or at anthesis. Spraying for FHB on winter wheat in these areas is recommended. Caramba and Prosaro have proven to be the best products for FHB control, however, timing of application is critical. These products must be applied at the beginning of anthesis with good efficacy achievable up to 5-7 days after the start of this growth stage. The FHB Prediction Center is forecasting moderate to severe FHB from Fond du Lac up through Door County for ‘very susceptible’ winter wheat varieties (Fig. 1). Wheat at the susceptible growth stage is at risk and spraying in these areas is recommended. Additionally, sprays at this time will also help manage foliar diseases such as rust that may move in and reduce yield during grain fill.

Figure 2. Stripe Rust Pustules on a Winter Wheat Leaf

Figure 2. Stripe Rust Pustules on a Winter Wheat Leaf

Brian Mueller, graduate student in my program, observed the first pustules of stripe rust on winter wheat in Wisconsin in 2015 (Fig. 2). These pustules were found in Sharon, WI in the UW wheat variety trial on June 4. This location is west of Janesville, near the Illinois border. Pustules were located in just one plot on a single variety during that first visit. Scouting was conducted again on June 10 in wheat not treated with fungicide next to the UW variety trial at this same location. Additional stripe rust infections were observed, however, severity remains low. I suspect stripe rust will continue to increase in this area and areas to the north. Cool wet weather is predicted for the next 5-7 days. This weather pattern will be conducive for stripe rust spread.

Figure 3. Cephalosporium Stripe symptoms on Winter Wheat.

Figure 3. Cephalosporium Stripe symptoms on Winter Wheat.

Cephalosporium stripe (Fig. 3) has also been identified in several fields around the state. Cephalosprorium stripe has been identified in winter wheat fields in Wisconsin over the last several years. Typically the disease has occurred in localized areas of the field, but in some cases it has been identified in wider areas depending on the varieties. 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.

No other disease have been observed on winter wheat in Wisconsin this week. We will be scouting variety trials in the northeast later this week. We will continue to report any diseases we observe.

 

Wisconsin Winter Wheat Disease Update: June 3

Figure 1. Fusarium head blight advisory for June 3, 2015 for a 'very susceptible' winter wheat variety.

Figure 1. Fusarium head blight advisory for June 3, 2015 for a ‘very susceptible’ winter wheat variety.

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

We have scouted wheat from South of Madison, Wisconsin up through to near Fond du Lac this week. Most winter wheat we have looked at has headed and quickly approaching anthesis. The winter wheat variety ‘Kaskaskia’ was at early anthesis today. Now is the time to make a decision on spraying for Fusarium head blight (FHB). The Fusarium Head Blight Prediction Center (http://www.wheatscab.psu.edu) has the majority of Wisconsin listed at low risk for a susceptible winter wheat variety. However, clicking the box to run the prediction for a ‘very susceptible’ winter wheat variety changes much of the state to medium risk and some areas at ‘high risk’ for FHB (Fig 1). With the warm and dry weather this week, the question has been “Should I spray for FHB?” In short, I think the answer to this question is ‘yes’ especially for farms and fields that have had a history of FHB.

If we consider the biology of the fungus and the epidemiology of FHB, the past, present, and future weather patterns are all important. Weather over the past couple of weeks has been rainy and wet. This has served to ‘prime’ the FHB fungus to make spores. Even with the dry weather this week, there is bound to be spores of the FHB fungus present and blowing around. Now if we consider the weather over the next few days, it looks like a pretty good chance for on-and-off rain with warm conditions; weather just ripe for FHB. Considering the conditions and the fact that anthesis is occurring this week, I think spraying is a good decision. Additionally, the fungicide applications at this stage will protect flag leaves from foliar diseases like rust, Septoria leaf blotch, or powdery mildew, should they move in over the next few weeks during grain fill.

Caramba and Prosaro have proven to be the best products for FHB control, however, timing of application is critical. These products must be applied at the beginning of anthesis with good efficacy achievable up to 5-7 days after the start of this growth stage. Fungicide application after 7 days post-anthesis is not recommended. You can watch a video of Dr. Shawn Conley describing how to identify this important growth stage by clicking here.

We continue to look for other wheat diseases around the state. We have not observed any rust on winter wheat in Wisconsin. Additionally, no powdery mildew and no Septoria leaf blotch have been observed on our scouting trips. We will continue to monitor the winter wheat disease situation as we move into grain fill.

Wisconsin Winter Wheat Disease Update – May 26

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

Winter wheat in the south and south-central portions of Wisconsin is quickly approaching heading. Most wheat we have looked at recently is at boot stage with some beginning to head. Anthesis (flowering) will be occurring very soon if it hasn’t already happened in these fields. Now is the time to consider Fusarium head blight (FHB or scab) risk and consider your control options in at-risk fields. With anthesis occurring this week in some fields, and the prolonged wet weather forecast for this week, growers and consultants should pay close attention to this situation. The risk for FHB will likely be high this week especially on susceptible varieties.  To learn more about FHB on wheat you can download a fact sheet by CLICKING HERE.

In addition to considering the weather conditions, you can consult the FHB Prediction Center. I recently wrote a post about the FHB Risk Tool and how to best use it. You can read more about the tool BY CLICKING HERE. Currently, the risk tool is predicting medium to high risk only along the Lake Michigan shore. However, I think this will change as we proceed through the week.  With the extended chances of rain and high humidity, coupled with moderate to warm temperatures, risk for FHB on susceptible and moderately susceptible cultivars will be medium to high across a wider portion of the state. This will be especially true along the southern portions of Wisconsin where wheat is  beginning to flower this week. Caramba and Prosaro have proven to be the best products for FHB control (see the Small Grains Fungicide Efficacy Table), however, timing of application is critical. These products must be applied at first flower with good efficacy achievable up to 5-7 days after the start of anthesis.  Fungicide application after 7 days post-anthesis is not recommended. Pay close attention to the FHB situation this week.

Other wheat diseases in Wisconsin have been fairly minimal. My graduate students managed to find and identify low levels of spot blotch on some plants at our Sharon, WI and Arlington, WI locations last Friday (May 22). The severity was relatively low. Rust and other diseases have not been identified in wheat fields we have traveled to. We will continue to scout and monitor the wheat disease situation as we head toward anthesis.

New Forecasting System for Fusarium Head Blight Now Available

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

Fusarium head blight (FHB or scab) was a very damaging disease for many winter wheat growers in Wisconsin in 2014. This disease is caused by a fungus called Fusarium graminearum and infects the heads when the wheat flowers are open. Not only does the colonization of the fungus into the grain cause a reduction in kernel size and overall development, but also the fungus can produce a toxin called deoxynivalenol or vomitoxin. Vomitoxin can be extremely toxic to not only humans, but also livestock. For more information about the specific biology and management of FHB, CLICK HERE to download a fact sheet.

One of the primary methods of controlling FHB in-season is to spray fungicide. Much work has been done by university extension pathologists to determine the best time to spray fungicide to control the disease. It turns out that fungicides targeted at the anthesis (beginning flowering stage or Feekes 10.5.1) period do a good job of protecting the plants and controlling FHB. Additionally, we now know that fungicide applications up to 5 days after anthesis can also be effective in controlling FHB. Application of fungicide 7-10 days after anthesis will offer minimal control based on university research trials sponsored by the US Wheat and Barley Scab Initiative. For a list of products with efficacy on FHB, consult the 2015 Small Grains Fungicide Efficacy Table BY CLICKING HERE.

As you can tell, the timing of application of fungicide is critical for controlling FHB. You can apply the best product available, but if it goes on too early or too late, the application will be wasted. Furthermore, in some years, weather conditions will not be conducive for onset of FHB. This means that if it is really dry during the anthesis (flowering) period, infection by the FHB fungus will be low and little disease will develop. An application during dry weather at flowering will mostly be unnecessary. In order to assist growers and consultants on making fungicide application decisions to control FHB, an online FHB forecasting tool was developed. The tool can be found here: http://www.wheatscab.psu.edu.

Figure 2. FHB Forecasting System Control Panel

Figure 2. FHB Forecasting System Control Panel

In previous years, the tool has tended to under-predict FHB infection events and under-represent the amount of FHB in Wisconsin. After more data was collected and new models were assembled, a new version of the FHB forecasting system has just been released to try to improve the accuracy of the FHB forecasting system. This new 2015 release is now active and functions automatically when you visit the link above. An additional change for 2015 in the winter wheat model is the addition of susceptibility levels for the winter wheat variety you are growing. Previously, the ‘susceptibility’ choice was not available for winter wheat. Consult your seed guide to determine the level of susceptibility for your variety in order to make this input. If you can’t find this rating, then simply choose ‘susceptible. After reviewing the model and the new forecasting system at our annual wheat disease workers meeting, I think that this system is a good improvement over the other forecasting system. I believe that this system has a model with better predictive accuracy. Of course, this does not mean that it can’t fail, but should be a good tool for decision-making purposes. Remember, that your working knowledge and previous experiences are still good predictors of FHB. So even if the model is saying that risk is low and your gut says it is high, go with the ‘boots-on-the-ground’ observations and your gut.

The best time to consult the FHB forecasting system is prior to heading, and through the anthesis period. Begin consulting the model when wheat is in the boot to get a feel for the risk conditions that lead up to the flowering period in your area. Once heads have emerged and flowers are beginning to open, daily consultation of the model can assist in making that decision to spray during that critical Feekes 10.5.1 timing.

You should find the model fairly easy to use. After clicking on http://www.wheatscab.psu.edu you will be brought to the main page (Fig. 1). Enter your state (step 1) and then choose the wheat class (winter or spring) in step 2 (Fig 2). The model will update in real-time, giving you color coded risk levels. You can also choose a forecast (up to 72 hours ahead) in step 3 (Fig. 2). Additionally, your state wheat pathologist will have most likely written a commentary in the text box at the top of the page, once you have chosen your state. In Wisconsin, I try to update this weekly, especially during the critical time for controlling FHB. Remember to keep scouting and paying attention to the weather, in addition to consulting the FHB forecasting system. Here’s to an FHB-free season!