Wisconsin Winter Wheat Disease Update – May 8

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The Wisconsin Field Crops Pathology lab scouted winter wheat from near the Southern Wisconsin state line (Janesville, WI) up to Arlington, WI (south central Wisconsin) yesterday. Wheat in this southern and south-central region in jointing or beginning to joint (depending on variety). Wheat generally looks very good with minimal issues at this stage. Variety trials also are looking good, with all varieties looking relatively clean. No stripe rust has been identified in these locations yet. However, we will be keeping close tabs on this given the severity levels of stripe rust in states to our south.

At the Arlington location we did find Septoria leaf blotch on early season tillers of the variety ‘Kaskaskia’. This was at very low incidence and severity levels and I would classify it as spotty at this point. However, weather conditions are forecast to be cool and rainy for the coming week, so this may result in an increase in severity. We will continue to monitor this situation and continue scouting wheat further north in the coming weeks.
Growers and consultants are encouraged to continue to scout, scout, and scout!

Stripe Rust on Wheat: Stay Alert!

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

Figure 1. Stripe rust on winter wheat leaves.

Figure 1. Stripe rust on winter wheat leaves.

I recently visited some wheat plots in southern Wisconsin. As in previous weeks, wheat is looking good and tillering well and nearing the jointing stage. Few disease issues have yet to be identified. In states to our south and west, such as Kansas and Nebraska, this has not been the case. Stripe rust has been identified in some of these areas and has been classified as moderate to severe depending on the variety of wheat. While, not yet a concern on wheat in Wisconsin, wheat farmers and crop consultants need to be paying attention to this potential threat. Typically in years where stripe rust is an issue in the southern wheat belt, Wisconsin will also see the disease.

Stripe rust or yellow rust (Fig. 1) of wheat is caused by the fungus Puccinia striiformis. This

Figure 2. Yellow pustules indicative of stripe rust on a wheat leaf.

Figure 2. Yellow pustules indicative of stripe rust on a wheat leaf.

fungus is in the same group of organisms that cause other rust diseases of wheat such as leaf rust and also the famed stem rust, which put the importance of wheat breeding on the map. 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 (Fig. 2). The color of the bright yellow stripe rust pustules is very different from the brick-red pustules that are common with leaf rust (Fig. 3) or stem rust.

The stripe rust pathogen survives on wheat debris as spores or mycelium (fungal threads) in areas where the temperatures don’t get above 90 F or below 20 F. It is thought that stripe rust cannot overwinter in the far northern areas of the U.S. such as Wisconsin. Little is know if the stripe rust fungus can survive the summers in Wisconsin, once the wheat crop has been harvested. We have a graduate student who will be working to address this and other questions about stripe rust on winter wheat in Wisconsin.

Figure 3. Brick-red Leaf rust pustules on a winter wheat leaf.

Figure 3. Brick-red Leaf rust pustules on a winter wheat leaf.

Because survival of the fungus might be limited in Wisconsin, the stripe rust pathogen most likely has to be windblown from the southern states into our wheat production area. This is why we need to pay close attention to stripe rust reports from the southern states. These reports are indicating that we will likely see stripe rust in wheat in Wisconsin this season and we may see it earlier than usual.

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. 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. Although, scouting wheat now can’t hurt either. Continued scouting through heading and anthesis (flowering; Feekes 10.5.1) can also help with making a decision to apply fungicide for leaf diseases and head diseases. For information on fungicides effective for controlling stripe rust, consult the 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.

Remember to SCOUT, SCOUT, SCOUT!

Wisconsin Winter Wheat Disease Update – April 15, 2015

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

Figure 1. Winter wheat plants in a field in Southern Wisconsin

Figure 1. Winter wheat plants in a field in Southern Wisconsin

This week I scouted winter wheat in research trials located at the Arlington Agricultural research station and also some commercial fields in southern Wisconsin. Wheat in these locations has greened up and is beginning to tiller (Fig. 1). I have observed very little winterkill on winter wheat in the fields I have looked at. Overall the winter wheat crop is looking good at these early stages with stands looking strong for the most part (Fig. 2).

Unlike the last couple of years, I have not observed any wheat diseases yet. Sometimes, Septoria leaf blotch can be observed very early in Wisconsin. We should begin to scout for diseases during these early tillering periods. If you find that Septoria leaf blotch is already present in wheat fields, then the base is set to build disease quickly if conditions are cool and wet this spring. If the spring turns to being cool and wet and a susceptible variety present, then this disease will increase and can cause enough damage to limit grain yield. To learn more about leaf blotch disease on wheat, consult THIS FACT SHEET.

Figure 2. Winter wheat stand in southern Wisconsin

Figure 2. Winter wheat stand in southern Wisconsin

Another disease to scout for at these early stages of wheat development is powdery mildew. This disease starts out as a white fluffy growth on the surface of the leaves and can progress quickly when humidity is high and temperatures fluctuate from warm days to cool nights. As the disease progresses, it can continue to cover more leaves, and the white growth may become more gray or brown in appearance. Like Septoria, if you notice early infections of powdery mildew, you have a susceptible variety planted, and conditions are conducive for the disease, then careful monitoring will be critical for making decisions about in-season control. To learn more about powdery mildew on wheat, consult THIS FACT SHEET.

Spraying fungicide when plants are very young (prior to jointing) isn’t generally recommended in Wisconsin. However, spraying to protect the flag leaf and later growth stages during heading can help preserve yield when this disease is a problem. In 2013 we conducted a fungicide trial on wheat where Septoria leaf blotch was the main disease of concern. In that trial we found that applications of fungicide at the early flag leaf emergence stage (Feekes 8) gave us good control of Septoria leaf blotch, which translated into giving us a yield increase over not spraying or spraying prior to jointing (Feekes 5). To read more about the results of this fungicide trial, you can visit THIS WEBPAGE.

In 2014, conditions were not very favorable for leaf diseases on winter wheat. However, Fusarium head scab was prevalent throughout much of Wisconsin. In our 2014 fungicide efficacy trials, we found that spraying at flag leaf emergence (Feekes 8) did not offer much yield advantage. However, spraying at anthesis (first flower; Feekes 10.5.1) did provide a significant increase in yield and significantly reduced the level of vomitoxin in grain samples. To read more about the results of the 2014 fungicide trial, you can visit THIS WEBPAGE.

The 2013 and 2014 field trials demonstrate the importance of frequent scouting of wheat to determine the right timing of fungicide application. In some years, you might need to spray at Feekes 8, in others at Feekes 10.5.1, while in some years at both timings.

In addition to the results of our field trials, you might also consult the 2015 Small Grains Fungicide Efficacy Table that was recently updated. This table offers unbiased, university research-based ratings of fungicides used on small grains. It is compiled by university research and extension pathologists from all over the country. You can find the latest table by CLICKING HERE.

It is a good idea to begin scouting now to determine what diseases are already present in wheat. Continue to watch weather forecasts as the crop matures and make plans for disease intervention measures (such as fungicide) if conducive disease conditions are present near flag leaf emergence and/or heading later this season. SCOUT, SCOUT, SCOUT!

New Wheat Powdery Mildew Fact Sheet

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A new fact sheet concerning powdery mildew of wheat has recently been published. The fact sheet describes symptoms of the disease and how to best manage it. To obtain a PDF version of the fact sheet, visit the ‘fact sheet’ section of the UW-Madison Field Crops Pathology website or CLICK HERE TO DOWNLOAD.

Fusarium Head Blight and Other Winter Wheat Diseases in Wisconsin, 2014

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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.

Winter wheat in most of Wisconsin is maturing nicely and starting to dry down in the southern portions of the state.  For most of the season, wheat diseases have been at low levels in Wisconsin.  However, certain areas of the state have been identified with high levels of Fusarium head blight (scab) in the last week.  These areas include Fond du Lac up through to Chilton and likely northward.  Growers and consultants should scout fields now to estimate the level of scab present in their fields.

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 deoxynivalenol (also known as 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 near our Fond du Lac location is maturing making it very difficult to assess the incidence and severity of the infection. Understanding a fields risk will help growers either field blend or avoid highly infected areas so entire loads are not rejected.
  2. 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.
  3. Know your elevators inspection and dockage procedure (each elevator can have a different procedure).
  4. Scabby kernels does not necessarily mean high DON levels and vice versa.
  5. DON can be present in the straw so there is concern regarding feeding or using scab infected wheat straw.  DO NOT use straw for bedding or feed from fields with high levels of scab (Cowger and Arellano, 2013).
  6. Do not save seed from a scab-infected field. Fusarium graminearum can be transmitted via seed. Infected seeds will have decreased growth and tillering capacity as well as increased risk for winterkill.
  7. Do not store grain from fields with high levels of scab.  DON and other mycotoxins can continue to increase in stored grain.
  8. For more information on Fusarium head blight click here.
  9. For More information on harvesting click here.

Other Wheat Diseases in Wisconsin

In general foliar diseases on wheat were present in low levels this year.  Some Septoria/Stagnospora leaf blotch was observed on wheat around the Arlington and Fond du Lac areas.  Severity was low at 10-20% on the lower leaves and less than 5% on the flag leaves.  Yield loss from Septoria/Stagnospora leaf blotch will be negligible this year.

Leaf rust was observed on several varieties of winter wheat throughout the wheat growing area of the state this year.  Severity on flag leaves was 10% or less and it did not typically become apparent until late in the growing season.  Yield loss from leaf rust will also be low this year.

Stripe rust was virtually non-existent this season in Wisconsin.  Only two leaves at our Arlington variety trial were found with stripe rust pustules.  Stem rust was also observed at this location in one plot, and not found at any other site that we visited this year.  Yield loss from stripe rust and stem rust will be negligible this year in Wisconsin.

Powdery mildew was not observed in any field we visited this year.

At the Fond du Lac variety trial, high levels of Cephalosporium stripe were noted on certain varieties.  This location has seen short rotations between wheat crops, likely contributing to this epidemic.  We also noted high incidence (90%) of bacterial leaf streak on several varieties at this location and the Chilton, Wisconsin location.

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 27

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Wheat Stem Rust

Wheat Stem Rust

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

My graduate students and I scouted and rated Shawn Conley’s State Uniform Winter Wheat Variety Trial at the Arlington Agricultural research station located in Columbus, County Wisconsin yesterday (June 26).  We were able to find leaf rust in many plots with incidence of this rust at 100% in many plots, but severity at no more than 10% on flag leaves.  Rust samples have been sent from this location to the Cereal Disease Lab in Minnesota for race typing.

My students were also able to find several very small foci of stripe rust.  Just 2 flag leaves found in 2 separate plots with just 10 or so pustules on each flag leaf.  So both incidence and severity is extremely low for stripe rust at this location.  This is very different than the past 2 seasons where we have had extremely high incidence and severity of stripe rust by this point in the season.  I suspect stripe rust will be of low impact for us this season in Wisconsin.
My students were also able to find a single plot with about 5 plants with stem rust.  I have attached a picture (not great quality) showing the characteristic pustules cracking through the epidermis of the wheat stem.   This was the only plot where we observed stem rust.  We will continue to monitor the rust situation in Wisconsin.  However, the severity of rust is very low for this point in the season.  The impact on yield from rust will likely be low as plants are quickly approaching the dough stage and rust severity remains generally low across most varieties.

Wisconsin Winter Wheat Disease Update – June 24, 2014

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Figure 1. FHB Risk Map for June 24, 2014

Figure 1. FHB Risk Map for June 24, 2014

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

I have spent the last several days rating winter wheat variety trials and fungicide trials at the Arlington Agricultural Research Station in Arlington, Wisconsin, Columbia Co.  Wheat in this area is mostly in the mid-to-late milk stage.

Leaf rust was observed at low levels in border rows and plots not sprayed with fungicide.  Incidence (number of plants with symptoms) in some plots is near 50%.  However, severity (area of leaf covered by rust pustules) on flag leaves is low at 5% or less.  At this stage impact on yield by leaf rust will likely be low and fungicide sprays to control the disease at this stage are NOT recommended.

Septoria/Stagopsora leaf blotch was also observed on lower leaves of most plots.  Very few plots had leaf blotch symptoms on the flag leaves, and if they did, severity was in the 5% range. Impact on yield by leaf blotch at this location will be low.  Again, fungicides are NOT recommended on winter wheat at this growth stage.

Very little Fusarium head blight (scab) has been observed on winter wheat from Arlington, Wisconsin on up through to Chilton, Wisconsin. Currently the Fusarium Head Blight Prediction Center (http://www.wheatscab.psu.edu) is predicting moderate to high risk for head blight for much of the state of Wisconsin (Fig. 1).  Winter wheat in much of the state is likely past flowering now, and thus the window of opportunity to treat for head blight has passed. However, some late-planted barley may be emerging from the boot at this time and this is the window of opportunity to control scab on barley, especially with the risk being moderate to high.

If a fungicide is warranted for control of scab on barley, products such Prosaro, Caramba, or similar that contain triazole active ingredients can offer suppression of scab and reduce deoxynivalenol (DON) accumulation in harvested grain.  These products should be applied within a week from the beginning of flowering for reasonable control.  Products containing strobilurin fungicides should be avoided after heading.  Research has demonstrated that levels of DON can be higher after treatment with strobilurin products after heading.

Wisconsin Winter Wheat Disease Update – June 19, 2014

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

I have scouted winter wheat fields and variety trials from Arlington Wisconsin up through Chilton Wisconsin this week, between rain showers.  Wheat in these areas is nearly finished flowering.  The window of opportunity to spray fungicides in these areas to control Fusarium head blight (scab) in winter wheat has now passed.

Figure 1. FHB Prediction Center Risk Assessment for June 19.

Figure 1. FHB Prediction Center Risk Assessment for June 19.

Currently the Fusarium Head Blight Prediction Center (http://www.wheatscab.psu.edu) is predicting moderate to high risk for head blight for the Door county peninsula and areas immediately adjacent to Green Bay (Fig. 1).  Winter wheat that is currently flowering in this area of the state is at high risk for infection by the fungus that causes scab. The prediction center is currently predicting low levels of scab in other parts of the state. This should be monitored closely by growers with barley. Some late-planted barley will be emerging from the boot soon and this is the window of opportunity to control scab if conditions are conducive.  With all the rain and warm temperatures across the state this week, I would suspect that the risk for scab on barley and any remaining flowering winter wheat will be elevated this weekend across much of the state.

If a fungicide is warranted for control of scab on winter wheat in the Door County area or barley, products such Prosaro, Caramba, or similar that contain triazole active ingredients can offer suppression of scab and reduce deoxynivalenol (DON) accumulation in harvested grain.  These products should be applied within a week from the beginning of flowering for reasonable control.  Products containing strobilurin fungicides should be avoided on wheat that has headed.  Research has demonstrated that levels of DON can be higher after treatment with strobilurin products after heading.

Figure 2. Cephalosporium Stripe symptoms on Winter Wheat.

Figure 2. Cephalosporium Stripe symptoms on Winter Wheat.

While scouting winter wheat fields at University of Wisconsin variety trials in the southern and eastern part of Wisconsin this week, I observed no rust or powdery mildew.  Trace levels of barley yellow dwarf were noted at all locations. At the Fond du Lac variety trial, high levels of Cephalosporium stripe (Fig. 2) were noted on certain varieties.  This location has seen short rotations between wheat crops, likely contributing to this epidemic.  We also noted high incidence (90%) of bacterial leaf blight on several varieties at this location. Some bacterial leaf streak was also observed, but incidence was less than 10%. Very low levels of Stagnospora/Septoria leaf blotch were noted. Most varieties had just completed flowering at this location and no scab was observed as of yet.

At the Chilton Variety trial, diseases are nearly absent.  The only disease noted on several varieties was bacterial mosaic at low incidence (<5%).  Cereal leaf beetle damage was moderate across many varieties in this trial.  Larvae were also found on flag leaves, but levels were below the economic threshold as of Tuesday.  Again at this location, most varieties had just completed flowering and no scab was observed as of yet.

Wisconsin Winter Wheat Disease Update – June 2, 2014

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FHB Update for Wisconsin - June 2, 2014

FHB Update for Wisconsin – June 2, 2014

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

Winter wheat in the southern portion of Wisconsin is at, or past, the flag leaf stage of growth. Disease reports have been few and far between this year.  This is because wheat looks very healthy. No diseases where observed on the wheat I inspected this weekend. Septoria leaf blotch I had observed very early this season has subsided and cannot be found now.  No powdery mildew was observed in these fields.  However, there have been several reports of very minor powdery mildew on wheat near the Janesville area.  Weather conditions have been very conducive for powdery mildew, so continue to scout for this disease.  If powdery mildew is observed at high levels of severity on flag leaves, then a fungicide application might be warranted.

No wheat rusts have been observed in the fields I have scouted this season.  I have received no reports of rusts on wheat in Wisconsin either.

In the next week or two, much of the wheat in Southern Wisconsin will be heading and flowering.  This is a critical time to control Fusarium head blight (scab).  If conditions are wet and warm during the flowering (anthesis) period, the risk for scab will be higher.  To assist in making decisions about scab management, consult the Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu.  Currently, the risk for scab is low in most of the state.  However, as temperatures get warmer and if it continues to rain, the risk can increase quickly.

If a fungicide is warranted for control of scab, products such Prosaro, Caramba, or similar that contain triazole active ingredients can offer suppression of scab and reduce deoxynivalenol (DON) accumulation in harvested grain.  These products should be applied within a week or so of the beginning of flowering for reasonable control.  Products containing strobilurin fungicides should be avoided on wheat that has headed.  Research has demonstrated that levels of DON can be higher after treatment with strobilurin products after heading.

Continue to scout wheat regularly over the next couple of weeks.  This will be a critical time to make in-season disease management decisions.

Wisconsin Winter Wheat Disease Update – April 16, 2014

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

Figure 1. A stand of winter wheat at the Arlington Agriculture Research Station. Photo take April 11, 2014.

Figure 1. A stand of winter wheat at the Arlington Agriculture Research Station. Photo take April 11, 2014.

This week I scouted winter wheat in research trials located at the Arlington Agricultural research station.  Wheat in the southern part of Wisconsin is starting to green up a bit (Fig. 1).  In this location snow cover was pretty consistent throughout the very cold winter months.  Survival of wheat plants was pretty good with the consistent snow cover.  I was worried about snow mold development given the duration of snow cover this year, however, none was observed in this location.

I did observe Septoria leaf blotch on a few of the plants in these plots already this season.  It is possible that the fungus infected these plants last fall, and the pathogen was able to overwinter.  Regardless of when these initial infections took place, this is a disease we need to scout for now and keep track of through the season.  If it is already present in wheat plots, then the base is set to build disease quickly if conditions are cool and wet this spring.  In figure 2, you can see a lesion of Septoria leaf blotch with pycnidia (fruiting structures) that can produce lots of spores that can be rain splashed to other leaves and plants.  Should the spring remain cool and wet, and a susceptible variety present, then this disease will increase and can cause enough damage to limit grain yield.  To learn more about leaf blotch disease on wheat, consult the fact sheet located here: /files/2013/04/Leaf-Blotch-Diseases-of-Wheat-1.pdf.

Figure 2. A Septoria leaf blotch lesion on winter wheat. Note the black pimple-like fruiting structures (pycnidia) present in the center of the lesion. These structures are very diagnostic for Septoria leaf blotch.

Figure 2. A Septoria leaf blotch lesion on winter wheat. Note the black pimple-like fruiting structures (pycnidia) present in the center of the lesion. These structures are very diagnostic for Septoria leaf blotch.

Spraying when plants are very young (prior to jointing) isn’t generally recommended for this disease.  However, spraying to protect the flag leaf and later growth stages during heading can help preserve yield when this disease is a problem.  In 2013 we conducted a fungicide trial on wheat where Septoria leaf blotch was the main disease of concern.  In that trial we found that applications of fungicide at the early flag leaf emergence stage (Feekes 8) gave us good control of Septoria leaf blotch, which translated into giving us a yield increase over not spraying or spraying prior to jointing (Feekes 5). To read more about the results of this fungicide trial, you can visit the webpage found at this link:/wheat/2013winterwheatfungicide/.  It is a good idea to begin scouting now to determine what diseases are already present in wheat. Continue to watch weather forecasts as the crop matures and make plans for disease intervention measures (such as fungicide) if conducive disease conditions are present near flag leaf emergence later this season.

No other diseases were observed on winter wheat this week.  Hopefully it will quite snowing and spring will arrive soon!