2018 Wisconsin Field Crops Pathology Fungicide Tests Summary Now Available

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Each year the Wisconsin Field Crops Pathology Program conducts a wide array of fungicide tests on alfalfa, corn, soybeans, and wheat. These tests help inform researchers, practitioners, and farmers about the efficacy of certain fungicide products on specific diseases. The 2018 Wisconsin Field Crops Fungicide Test Summary is now available. These tests are by no means an exhaustive evaluation of all products available, but can be used to understand the general performance of a particular fungicide in a particular environment. Keep in mind that the best data to make an informed decision, come from multiple years and environments. To find fungicide performance data from Wisconsin in other years, visit the Wisconsin Fungicide Test Summaries page. You can also consult publication A3646 – Pest Management in Wisconsin Field Crops to find information on products labeled for specific crops and efficacy ratings for particular products. Additional efficacy ratings for some fungicide products for corn foliar fungicides, soybean foliar and seed-applied fungicides, and wheat foliar fungicides can be found on the Crop Protection Network website.

Mention of specific products in these publications are for your convenience and do not represent an endorsement or criticism. Remember that this is by no means a complete test of all products available.  You are responsible for using pesticides according to the manufacturers current label. Some products listed in the reports referenced above may not actually have an approved Wisconsin pesticide label. Be sure to check with your local extension office or agricultural chemical supplier to be sure the product you would like to use has an approved label.  Follow all label instructions when using any pesticide. Remember the label is the law!

2018 Pest Management Update Meeting Series Announced

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The schedule for the Wisconsin Pest Management Update meeting series has been set. Presentations will include agronomic pest management information for Wisconsin field and forage crops. Speakers include Mark Renz and Rodrigo Werle, weed scientists, Damon Smith, plant pathologist, and Bryan Jensen, entomologist.

The format will be the same as in 2017. Meetings will either be in the morning or afternoon On November 12-16, 2018. Simply choose a day/location to attend with each meeting running 3 hours. Note that several locations and contacts have changed since 2017 (marked with * in the meeting flier). Please read the informational flier carefully and make sure you contact the appropriate person at your desired location.

2018 Pest Management Update Highlights:

  • Integrated Pest Management Updates in corn, soybeans, alfalfa, and small grains: Update on new products and/or use of existing products as well as brief highlights of the 2018 pest situations in each crop.
  • Waterhemp management
  • Dicamba off-target research
  • Pollinator Training
  • Soybean cyst nematode training and management

Please make your reservation with the host contact at least one week prior to the scheduled meeting date.

Three hours of Certified Crop Advisor CEU credits in pest management are requested for each session.

To download a PDF of the flier, CLICK HERE.

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

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

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

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

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

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

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

What should I do to prepare for wheat harvest?

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

References

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

Wisconsin Winter Wheat Disease Update – June 26, 2018

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Fusarium head blight of winter wheat

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

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

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

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

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

Welcome to badgercropdoc.com: A New Web Resource for Wisconsin Field Crops Pathology Research and Outreach

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

Welcome to badgercropdoc.com! Badger Crop Doc is a one-stop-shop for all things Wisconsin Field Crops Pathology related. We have merged the website and blog found at / with our University of Wisconsin academic website, so that all information can now be found in one place. If you subscribed to the blog posts at /, don’t worry, we have already moved your e-mail over to badgercropdoc.com. Be sure that browsers are now pointed to the new URL and check your e-mail folders to be sure blog postings aren’t going to junk or trash. No new postings will be added to /.

BadgerCropDoc was made possible with support from the Wisconsin Soybean Marketing board and is meant to be complementary to badegrbean.com and coolbean.info, while offering research-based information for the major field crops of Wisconsin. We hope you enjoy this new resource. As always, please let us know what you think. We would love to hear feedback.

Wisconsin Winter Wheat Disease Update – June 6, 2018

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

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

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

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

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

Wisconsin Winter Wheat Disease Update – May 30, 2018

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

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

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

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

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

Wisconsin Winter Wheat Disease Update – May 24, 2018

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

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

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

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

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

Wisconsin Winter Wheat Disease Update – May 21, 2018

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Winter wheat in the Uniform Variety Trial located in Sharon, Wisconsin in 2018

The Wisconsin Field Crops Pathology scouted winter wheat in the uniform variety trials located in Sharon and Arlington, Wisconsin late last week. The crop was jointing at both locations. The crop looks very good. We found no disease at either location. At this time last year we already had a significant epidemic of rust started across southern Wisconsin. Thus, the winter wheat crop is looking much better than this time last year, when it comes to the disease situation. We also took a quick look at a couple of production fields in the area and those also appear to be clean. We have also received some reports of wheat conditions around the Fond du Lac area. Wheat is reported to look very good there as well with no disease. We will try to also scout uniform variety trials in those locations in the next few days.

Despite good news, weather has been conducive for the development of foliar disease the last few days. I would encourage folks to be diligent in scouting. I would expect flag leaf emergence in the next 1-2 weeks across the winter wheat growing region of the state. We will be entering a very important time to make a decision about your first fungicide application. Considering the current agricultural economy, the decision to spray fungicide is going to be critical to try to break even this year. I would hold off as close to the anthesis growth stage to “pull the trigger” as you can wait. This will help maximize fungicide use to control both of the major diseases of wheat that we see in Wisconsin, stripe rust and Fusarium head blight (FHB; scab). However, if stripe rust shows up after flag leaf emergence, it might be necessary to apply a fungicide before anthesis to control a rust epidemic, especially on susceptible varieties. Based on previous research conducted by our laboratory in Wisconsin, we know that an application of fungicide that closely coincides with the start of the rust epidemic can be very effective in preserving yield on susceptible and moderate susceptible varieties. Many fungicides are effective in controlling stripe rust, including the industry leaders used for FHB control, Prosaro and Caramba. Therefore, if rust doesn’t show up in your field before anthesis occurs, you can effectively use Prosaro and Caramba to control both FHB and a late stripe rust epidemic. The best case scenario would be to only have to spray fungicide once this season. However, there is still much time left, so diligent scouting is critical to make the best decision. Get out there and SCOUT, SCOUT, SCOUT!

Wisconsin Winter Wheat Disease Update – April 17, 2018

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

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Winter wheat greening up after winter.

The Wisconsin Field Crops Pathology crew scouted the winter wheat uniform variety trials located in Sharon, Wisconsin late last week (April 12, 2018) prior to the latest snow storm. This is our most southerly location (near the IL state line), and is often a good early indicator of disease issues for Wisconsin. Wheat was trying to green up a bit, but the latest snow fall will surely set the crop back. With more snow in the forecast for April 18, 2018 it will be some time before we can scout wheat again for disease. That is the bad news. The good news is that we did not find any diseases.

With numerous reports of active stripe rust from states in the Mid-south we were concerned that early stripe rust might be present. We scouted known varieties to be susceptible, with no foliar symptoms apparent. You will remember in 2017, we identified active stripe rust very early in Wisconsin. This was due to overwintering of Puccinia striiformis inoculum from active infections that started in the fall of 2016. We suspect that warmer winter conditions in the 2016-2017 field season allowed P. striiformis to overwinter. Sharma-Poudyal et al. (2014) reported models that predict overwintering of P. striiformis when the 30-day average low temperatures are 14F or above with snow cover, or 21F or above without snow cover.

Figure 2. Average 30-day low temperatures, 2016-2017 30-day average low temperatures, and 2017-2018 30-day average low temperatures and P. striiformis survival thresholds under snow cover and without snow cover for Clinton, Wisconsin.

Using these thresholds and data from US Climate Data (https://www.usclimatedata.com/) for Clinton, Wisconsin (very close to our research site) in the 2016-2017 field season, we found that the under-snow-cover threshold was not below the 14F mark (Fig. 2). These warm conditions in 2016-2017 likely resulted in overwintering of inoculum at this location during last season. Using the same temperature thresholds and looking at 30-day average low temperatures for the 2017-2018 field season, we find that low temperatures where much more seasonable and were well below even the under-snow-cover threshold in January 2018 (Fig. 2). Thus, the risk for overwintering of P. striiformis inoculum in far southern Wisconsin is low this season. Even if active P. striiformis infections were found in fall of 2017, the likelihood it survived the winter was unlikely; especially considering the low temperatures in January of 2018 with minimal snow cover at this site during that time.

We will continue to scout winter wheat fields once snow melts. I would encourage others to get out and scout once the weather improves. Be sure to pay close attention to any winter wheat varieties that are known to be susceptible to stripe rust.

Literature cited:

Sharma-Poudyal, D., Chen, X., and Alan Rupp, R. 2014. Potential oversummering and overwintering regions for the wheat stripe rust pathogen in the contiguous United States. Int J Biometeorol. 58:987-997.