Wisconsin Winter Wheat Disease Update – May 24

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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!!

Wisconsin Winter Wheat Disease Update – May 11

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

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

Active Stripe Rust Pustules on a Winter Wheat Leaf in Sharon, Wisconsin.

Active Stripe Rust Pustules on a Winter Wheat Leaf in Sharon, Wisconsin.

It was only a matter of time….

Today we confirmed the first observations of stripe rust in Wisconsin for 2016. Brian Mueller, Graduate Research Assistant  in the Field Crops Pathology Lab at the University of Wisconsin-Madison found active stripe rust pustules in winter wheat in both southern and south central Wisconsin. In southern Wisconsin stripe rust was found in the Wisconsin Winter Wheat variety trial located in Sharon, Wisconsin. Stripe rust was at low incidence and severity on emerging flag leaves with some lesions manifesting as chlorotic flecks and not yet active. We speculate that the epidemic initiated recently. With the humid and rainy weather over the past several days, conditions have been ripe for symptom development.

The second stripe rust confirmation was at the Arlington Agricultural Research Station in an integrated management trial for stripe rust. Again, incidence and severity were low on emerging leaves, therefore, we speculate that the epidemic has recently initiated. We have been actively looking for stripe rust as there have been numerous reports of epidemics in winter wheat in states to our south and west. Given the recent weather patterns we will likely see more stripe rust show up in the state.

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

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

Stripe rust or yellow rust of wheat is caused by the fungus Puccinia striiformis. Stripe rust can be identified readily by the bright yellow pustules that typically occur in a striped pattern on the surface of the wheat leaf. The color of the bright yellow stripe rust pustules is very different from the brick-red pustules that are common with leaf rust or stem rust. For more information on the biology of the stripe rust pathogen, and signs and symptoms, PLEASE VISIT THIS PREVIOUS POST.

Management of stripe rust includes using resistant cultivars and applying fungicide, along with using some cultural practices such as avoiding excessive fertilizer applications and eliminating volunteer wheat plants. Obviously, winter wheat is already in the ground, so you cant make a decision on resistance for the current crop, but familiarize yourself with the stripe rust resistance rating for your wheat varieties. Knowing that certain fields might be more susceptible than others will help you determine where you should be scouting first.

Fungicide applications can also be useful for controlling stripe rust when properly timed with the onset of the epidemic. Frequent scouting of fields will help you to determine when stripe rust shows up and if an application of fungicide is needed to control it. Wheat will be most susceptible to yield loss if stripe rust infects plants prior to heading. In our fields in Arlington and Sharon, this disease will be a yield limiter, especially on susceptible cultivars due to the fact that it is already becoming active on emerging flag leaves. The later that stripe rust infects, the less the impact on grain yield will be. Scouting at or near the flag-leaf emergence growth stage (Feekes 8) can help with making the decision to apply a fungicide at this critical time period.  For information on fungicides effective for controlling stripe rust, consult the recently updated Small Grains Fungicide Efficacy Table found here.

For more information about stripe rust, check out the USDA Cereal Disease Laboratory Website. They have a stripe rust informational page, which can be viewed by CLICKING HERE.

Get out there and scout!  We are approaching a critical time to make a fungicide application decision in Wisconsin.

Wisconsin Winter Wheat Disease Update – May 6

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

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

Wheat

Winter Wheat Grown in Wisconsin

Winter wheat in research plots, and also adjacent production fields, was scouted in southern and south central Wisconsin during the week of May 2. Wheat at these locations ranges from Feekes 5 to Feekes 7. Wheat in general looks very good. Weather in the major wheat production area of Wisconsin has been generally dry this spring. This has resulted in very little disease pressure. We have been actively scouting for stripe rust considering reports from other states and have been unable to find any trace of rust, even in susceptible cultivars. As mentioned in a previous post, Septoria leaf blotch has been identified in low levels at some locations, however, the dry weather has lead to little progress of this disease. Powdery mildew has also been nearly nonexistent at this point.

Weather forecasts for the week of May 9 look to include some rain events. This may result in increased risk of disease onset, so this situation should be monitored carefully. We will continue to scout research plots, variety trials, and production fields for wheat diseases. As we move closer to the Feekes 8 growth stage (emerging flag leaf) the decision to spray fungicides will need to be made at that time. Remember that protecting the flag leaf from active foliar disease can be important, as that single leaf can be responsible for the majority of the grain yield of that plant. In Wisconsin, in years where leaf disease like Septoria leaf blotch or stripe rust have been active at the Feekes 8 growth stage, we have observed a significant increase in grain yield with fungicide applications at this time.  However, if conditions remain dry during this growth stage, fungicide application may not be necessary. Weather over the next several weeks will guide this decision-making process. If you are interested in learning more about effective fungicides and fungicide application timing for wheat, please visit the FUNGICIDE INFORMATION webpage or also check out fungicide efficacy trial summaries from past years on the SUMMARIES webpage.

After the Feekes 8 growth stage, the next critical growth stage for making a fungicide application decision will be at Feekes 10.5.1 growth stage or the start of anthesis. This application of fungicide will be applied to target Fusarium had blight (FHB or scab). The field Crops Pathology laboratory will continue to monitor the Wisconsin wheat disease situation. Please be sure to check back periodically for any new updates.

Wisconsin Winter Wheat Disease Update – April 13

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

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

Figure 1. Septoria leaf blotch on a young winter wheat plant.

Figure 1. Septoria leaf blotch on a young winter wheat plant.

Winter wheat in southern and south central Wisconsin was scouted on April 7 and 8, 2016 by the Wisconsin Field Crops Pathology research and extension crew. Locations of scouting included Sharon, Wisconsin near the Illinois border and Arlington, Wisconsin north of Madison. At both locations Septoria leaf blotch was observed on young, tillering winter wheat plants (Fig. 1). Septoria leaf blotch is caused by the fungus Septoria tritici. Typically this pathogen isn’t identified on wheat in Wisconsin until closer to flag leaf emergence. The presence of the pathogen this early in the season is likely due to the mild, wet conditions we have had this spring. Other common leaf blotch disease can be caused by other fungi such as Stagnospora nodorum or Stagnospora avenae f. sp. triticae. However, in Wisconsin the most common causal agent of leaf blotch is Septoria tritici. Septoria leaf blotch can often be diagnosed based on the presence of darkly pigmented fruiting bodies (Fig. 2) that exude gelatinous spore masses when incubated in a humidity chamber (Fig. 3). To definitely differentiate this fungus from Stagnospora nodorum, however, spores need to be examined microscopically in the UW Diagnostic Clinic. For information on how to submit samples, CLICK HERE. For more information on leaf blotch diseases of winter wheat in Wisconsin and management of these diseases, CLICK HERE TO DOWNLOAD AN EXTENSION FACT SHEET.

Figure 2. Fruiting bodies of the Septoria fungus on winter wheat leaves.

Figure 2. Fruiting bodies of the Septoria fungus on winter wheat leaves.

Under the current conditions this season, a fungicide application IS NOT recommended as the pressure is low and little yield loss would be expected from a light epidemic early in the season. However, growers and consultants should scout fields and monitor the situation carefully.  Should conditions continue to be mild and wet, disease may increase and require the application of fungicide to manage the disease. Past research in Wisconsin has demonstrated little need for application of fungicide prior to flag leaf emergence (Feekes 8 growth stage). In 2013, a significant epidemic of Septoria leaf blotch was present in a fungicide trial on winter wheat located in Arlington, Wisconsin. In that trial, the fungus that causes Septoria leaf blotch was active around the same time as noted this season. Application of fungicide at the Feekes 5 growth stage resulted in just marginal control of Septoria leaf blotch. To review the results of this trial, CLICK ON THIS LINK, and scroll to down to pages 9 and 10.

Figure 3. Gelatinous spore masses exuding from fruiting bodies of the Septoria fungus.

Figure 3. Gelatinous spore masses exuding from fruiting bodies of the Septoria fungus.

At all locations no stripe rust was observed. However, given recent reports of stripe rust occurring in locations in the Southern and central U.S., winter wheat growers should pay close attention to this disease. For more information about stripe rust and stripe rust management please check out our previous post from 2015 located by CLICKING HERE.

Be sure to check back to the blog frequently for winter wheat disease updates in 2016!

 

Results of the 2015 Wisconsin Winter Wheat Foliar Fungicide Trial

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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

Get a Jump on Winter Wheat Management This Fall

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

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

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

As we approach the 2015-2016 winter wheat planting season, it is important to consider some critical management opportunities that you might have now, to improve stands and manage disease later on. We have put together several articles in an effort to address these concerns. You can find these articles by clicking on the titles below.

Start Managing for Fusarium Head Blight Now Before You Plant the 2015/16 Crop

Top 8 Recommendations for Winter Wheat Establishment

Fusarium Head Blight a Significant Issue in Wisconsin in 2015

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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: 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

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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.

 

Stripe Rust on Winter Wheat Observed in Southern Wisconsin

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Stripe Rust Pustules on a Winter Wheat Leaf

Stripe Rust Pustules on a Winter Wheat Leaf

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

Brian Mueller, graduate student in my program, observed the first pustules of stripe rust on winter wheat in Wisconsin in 2015 (see attached image). These 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. No pustules were identified in other plots. We will continue to monitor the wheat rust situation over the next couple of weeks.

Wisconsin Winter Wheat Disease Update: June 3

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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.