Wisconsin Winter Wheat Disease Update – June 30, 2017

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

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

Brian Mueller, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin-Madison

The Wisconsin Field Crops Pathology team has nearly finished all of our assessments of wheat and wheat disease for the year in Wisconsin. Winter wheat is well on its way to maturing. The few spring wheat acres we have seen have mostly completed anthesis throughout much of the state, with just a few late-planted locations still completing anthesis.

Overall, the spring 2017 wheat season can be defined mostly by the widespread presence of stripe rust. We have been in fields where stripe rust has caused significant widespread damage on susceptible varieties that were not treated with fungicides. We have also observed fields that either had a resistant variety, received a fungicide application, or both. These fields appear to be doing quite well and the crop will yield well. Clearly areas where we suspect that there was overwintering of the stripe rust pathogen, saw the occurrence of the epidemic very early, resulting in quick spread of stripe rust this season. We have completed rating of stripe rust in the wheat variety trials in Wisconsin and these data will be published later this year in the variety performance report. I would encourage you to study these results carefully and choose varieties that performed well in your area and had low levels of stripe rust. This is the second year in a row that we have had a substantial stripe rust epidemic and choosing resistant varieties is a cheap method of stripe rust management.

We have also been looking for Fusarium head blight (FHB or scab) in commercial fields and variety trials. For a second year in a row, FHB incidence and severity is extremely low statewide. In many fields we struggle to find even one symptomatic head. Fusarium head blight incidence in the far southwest part of the state is nearly undetectable and approaches about 1% incidence in fields in the north-central and northeastern portions of the state. I expect that DON (vomitoxin) levels will be relatively low in finished grain in Wisconsin, this season. The low level os FHB in winter wheat this season is likely due to the unseasonably hot, dry weather we had in early June, which coincided with anthesis in many wheat fields. This type of weather is not conducive for the fungus and likely resulted in very few successful infection events.

Other diseases have been extremely hard to find. We have seen some fields with low levels of Septoria/Stagonospora, but in general these epidemics will not limit yield to a significant extent. Powdery mildew can be found infrequently on a few plants in some fields. In the southern portion of the state, we were able to find some leaf rust just this week. The arrival of leaf rust is likely too late to affect yield this season. We have not observed any stem rust in our scouting trips to commercial fields or in variety trials.

 

Wisconsin Winter Wheat Disease Update – May 6

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

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!

 

Wisconsin Winter Wheat Disease Update – April 15, 2015

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!