More Stripe Rust Found in Wisconsin Winter Wheat

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Stripe Rust Pustules on a Winter Wheat Flag Leaf

Stripe Rust Pustules on a Winter Wheat Flag Leaf

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

The Wisconsin Field Crops Pathology Lab scouted winter wheat variety trials located in Fond du Lac and Chilton, Wisconsin today (June 11). Stripe rust was found at both locations. At the Fond du Lac site rust was only found in a few plots, but some plants had high levels of severity on flag leaves (see image). At the Chilton site, more plots and varieties were symptomatic with stripe rust, but severity was trace or low for all plots.  In one plot at Chilton, we also observed one flag leaf with trace levels of leaf rust. Wheat at both sites is in full flower.

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.

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!