Disease Update 07/08/20

In my travels last week across northern Minnesota, I found little to no disease in the spring wheat trials or fields that I walked. I did find, however, plenty of standing water and drown outs. And, like in the southern part of the state, I did find the first signs of net blotch in barley.
On Monday I revisited the trials in LeCenter and in just 10 days since my last visit Bacterial Leaf Streak (BLS) had made its mark on the spring wheat trial. It was both amazing and disheartening to see how quickly BLS had torn through the canopy of some of the entries. Fortunately, there were also entries that to date had faired much better. These observations have been corroborated by reports from growers in southern Minnesota that have reported BLS to me.
The issue that is even more concerning than BLS is Fusarium Head Blight (FHB). The continued hot and humid weather across much of the state combined with the intermittent thunderstorms has meant and will mean that the risk of FHB infections has increased now to very high for varieties that are rated susceptible to very susceptible to the disease. The risk is now even moderate to high for varieties that are rated moderately susceptible or moderately resistant to FHB in many parts of the state.
The decision to apply a fungicide to suppress FHB is not a question of 'if' but a question of 'when' going forward. The immediate forecast continues to be hot and humid with scattered thunderstorms across much of the state. The only fields that are probably exempt are those that are in the pockets across the state that keep missing the thunderstorms and are actually drought-stressed.
The decision on whether to use tebuconazole or Prosaro/Caramba/Miravis Ace has not gotten any easier as the overall health and thus yield potential of the crop has been declining and likely will continue to decline with the continued hot weather and stress caused by the excess water. The later three fungicides each improve suppression of FHB by about 15% to 20% over tebuconazole.

--Jochum Wiersma, Extension Agronomist, University of Minnesota Crookston

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

According to the National Fusarium Risk model, risk continues to remain high for susceptible varieties that are flowering in Eastern ND and for an extended area in northwest North Dakota. For moderately susceptible varieties, risk is low for most of the state Recent rain events and higher nighttime humidity will likely increase FHB risk on susceptible varieties for most of the state (exception being southwest ND). Continue to monitor the growth stage in small grain fields to determine the best time to apply a fungicide (if warranted). The best time to apply a fungicide in wheat is at early flowering and up to seven days after the start of flowering. In barley, the best time to apply is at full-head and up to seven days after full-head.

--Andrew Friskop, Cereal Extension Pathologist, NDSU Department of Plant Pathology

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

In my travels last week across southern Minnesota, I found little to no disease in the spring wheat trials or fields that I walked. I found net blotch in one of the barley varieties (Pinnacle) that is very susceptible to this foliar pathogen and here and there was some tan spot in some of the winter wheat varieties. The most common and widespread, however, was BYDV. In production fields, these virus infections were the typical small circular patches or individual plants that showed the typical bright yellow flag leaves. In individual plots, these were often individual plants along edges of the plot. I found no leaf or stripe rust and it was a bit too early to see whether there were any of scab infections.

The risk of FHB increased in especially north of US Hwy 2 and across much of southern Minnesota (south of US Hwy 12), while conditions for tan spot remained high across much of the state. The notable exceptions for increased risk for FHB infections, or the foliar diseases, were the southern Red River Valley and west-central Minnesota. The very dry conditions I encountered in my trials near Benson explain why. There simply wasn't and still isn't enough moisture in the whole system to have leaf wetness periods long enough for any of the diseases to create initial infections.
The predicted heat for the coming week combined with the forecast of scattered thunderstorms will likely mean that the risk for FHB will remain high for varieties that are rated very susceptible or susceptible to the disease in those areas that already have adequate soil moisture. The risk for FHB infections will likely be moderate for varieties that are rated moderately resistant or better. If your barley or hard red spring wheat crop reaches anthesis (Feekes 10.51) this coming week, you will need to make a decision whether you choose tebuconazole or one Prosaro/Caramba/Miravis Ace. The later three fungicides each improve suppression of FHB by about 15% to 20% over tebuconazole. All products will provide very good to excellent control of any of the foliar diseases.

--Jochum Wiersma, Extension Agronomist, University of Minnesota Crookston

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

Most of the spring wheat is at or will soon be at flowering. One disease that can develop in wheat at this growth stage is Fusarium head blight (FHB or scab). The FHB pathogen infects the wheat head through the senescing flowers and can cause reduced yield and accumulation of mycotoxins, mainly deoxynivalenol (DON). Wheat grain with more than 2ppm can be docked for price at the elevators. The only in-season FHB management strategy is timely application of a fungicide at flowering. Since by the time FHB symptoms develop, it would be too late to apply a fungicide, an FHB prediction tool can be very helpful in gauging the risk for FHB. Currently, the FHB risk is showing to be moderate to high for a few areas in the eastern half of the state. For fields in these areas where spring wheat is at flowering, a fungicide is recommended to manage FHB. Keep checking on this FHB prediction tool when deciding on FHB fungicide application.

A few fungicides that are effective against FHB include Prosaro, Miravis Ace and Caramba. These fungicides have been tested widely in the region and provide protection against FHB and other fungal leaf diseases. Based on diseases developing in winter wheat such as powdery mildew, stripe rust, leaf rust, and tan spot; a fungicide applied for FHB management would also protect against these fungal leaf diseases.

--Emmanuel Byamukama, Extension Plant Pathologist , South Dakota State University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

Small Grains Disease Update 06/22/2020

Little changed in both the risk models or reports that I received this past week. I suspect there is some stripe rust and crown rust here and there across the southern half of the state, while tan spot is probably the only fungal disease you might find in the northern half of the state as of today.
That is likely to change in the near future as much needed rain fell across much of the state when a couple of cold fronts brought relief from the blast-furnace heat and wind of the first half of last week. While the risk of leaf rust infections has already started trending higher over the weekend for all but the northeastern edge of the state, the risk of infection for FHB will start to increase by tomorrow.
The heat in the first part of last week continued to push the development of the spring wheat crop and the first spring wheat fields reached heading over the weekend in the northwest part of the state. This means that you will need to actively scout individual fields to determine the current growth stage, and locate whether you have tan spot, stripe rust, or possibly even leaf rust near the bottom, middle, or top of the canopy.
The hot windy weather itself or the herbicides applied during the hot windy weather may have caused physiological speckling or discolorations that can easily be mistaken for one of the foliar fungal diseases. Remember that tan spot, septoria, stripe, and leaf rust almost always start near the bottom of the canopy and move upwards to newer leaves as the growing season progresses. You should therefore always find worse symptoms of the same diseases lower in the canopy. Bacterial Leaf Streak (BLS) is an exception to this rule of thumb.
While your scouting you may wonder what the yield potential of the spring wheat crop is. People have already commented to me that the crop seems very short this season. I'll repost a Minnesota Crop News article about the lack of height of the crop and whether that spells disaster before grain fill even has started.
The weather forecast for the coming week looks very favorable for grain fill for winter wheat, rye, and the earliest spring wheat, barley, and oat fields as daytime highs not forecasted to exceed 85 and nighttime lows will remain in the low to mid-fifties for much of the state.
Bring your rubber boots
--Jochum Wiersma, Extension Agronomist, University of Minnesota Crookston

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

Over the past week, there have been several reports of wheat and barley heading across the state and now is the time to start monitoring scab risk. Most areas of the state with a heading small grain crop are under low scab risk (drought stress), however there are a few pockets with higher risk. According to the model, risk is moderate to high for susceptible varieties in the eastern quarter of the state and for a small pocket in northwestern ND. Scab risk for moderately susceptible (score of 5-6 in the selection guide) and moderately resistant (score of 4 in the selection guide) varieties is low across the state. As a reminder, the best time to apply a fungicide for FHB in wheat is at early flowering, and the best time in barley is at complete head emergence.

--Andrew Friskop, Cereal Extension Pathologist, NDSU Department of Plant Pathology

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

Welcome to the Fusarium Head Blight Prediction Center, 2020. The system has undergone some revisions this year. The new interface focuses on the map-based risk of disease for the current date. Users can select other dates of interest from the menu in the upper portion of the interface. The date selected should correspond to times when your wheat is flowering, because the crop is most susceptible to infection at this stage. There is also a menu icon in the upper left corner that allows users to customize the model predictions for winter vs. spring wheat, and account for wheat varieties with different levels of genetic resistance to Fusarium head blight.

The focus of the prediction effort is currently on Northern South Dakota, Southern North Dakota, Central Minnesota, Wisconsin and the “thumb” area of Michigan where winter wheat is likely at the heading and flowering stages of growth. The models indicate a moderate or high level of risk for susceptible wheat varieties in portions of South Dakota, and North Dakota. Growers in these areas should consult with local advisors to determine what other local factors that might also influence the risk of disease.

--Erick De Wolf, Department of Plant Pathology, Kansas State University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

The first instances of stripe rust, crown rust, and barley yellow dwarf were confirmed in winter wheat and oats, respectively, this past week in southern Minnesota. Meanwhile, tan spot is prevalent in wheat following wheat in the northern half of Minnesota.

These findings are all in line with expectations/risk models. The conditions for tan spot, for example, have been favorable across much of the northern half of the state for seven out of the last ten days.
One of the characteristic symptoms of early-season tan spot infections is a yellowing discoloring of whole leaves. This is a more extreme expression of the same yellow halo that surrounds the tan spot lesions in more mature plants. Be careful not to mistake this yellowing for a nitrogen deficiency.

Research at both NDSU and the University of Minnesota has shown that the early onset of tan spot yield can results in yield reductions of 4 to 5 bushels if conditions continue to favor the development of the disease. Use half a labeled rate of a registered fungicide to halt/slow down the disease progression. Most of the labeled fungicides can successfully be tank-mixed with the commonplace herbicides. Always check the label of both the herbicide and fungicide for tank mix restrictions.

Research at the Northwest Research and Outreach Center has shown that the combination of any of the EC formulations of fungicides in combination with common wild oat herbicides and bromoxynil + MCPA can result in bromoxynil injury in both wheat and wild oats. This injury generally did not affect grain yield of the wheat or the control of the wild oat.

A nitrogen deficiency can readily be identified as the symptoms are worst on the oldest leaves and start at the tip of the leaves, progressing towards the base as the deficiency gets worse. This is in contrast to the yellowing caused by tan spot, which will start from the initial lesions and migrate up and down the leaf blade from the initial point of infection. The causes of the N deficiencies are several, all of which have a common denominator, namely excess precipitation. Excessive rainfall causes leaching, denitrification, and the inability of the plants to take up available N

Leaching is a potential problem in coarser textured soils. Saturated soils/standing water will cause both denitrification and inability to take up available N. As soils are saturated, the plant’s roots also are unable to take up N - even if available. Often the crop recovers quickly if the growing conditions improve and the excess water has drained. If the N deficiency is severe, a supplemental application of N as either urea (46-0-0) or urea ammonium nitrate solution (28-0-0) can be advantageous.

The earliest seeded spring wheat in the southern half of the state will likely reach anthesis sometime this week. To date, the risk models Fusarium head blight have been trending relatively low. This is largely the result of the lack of precipitation the past two weeks across a large swath of southern half of the State. The lower dew points further help reduce the risk of the disease to develop. Focus the scouting efforts on the presence of foliar diseases and still consider a fungicide application at anthesis if you detect tan spot, Septoria, and/or one of the rust on the flag leaf, penultimate leaf or the second leaf below the flag leaf.

--Jochum Wiersma, Extension Agronomist, University of Minnesota Crookston

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

Winter wheat is approaching flowering and some of the earliest planted barley may be heading this week. Currently, most of the state is at low risk for FHB, but a few pockets of moderate risk are developing in south central and northeastern ND. Most of the state received rain last week and the forecast for this week shows sporadic rain events with high dew point temperatures. As a reminder, the best time to apply a FHB fungicide in winter wheat is at early-flowering (and up to 6-7 days after) and the best time for barley is complete head emergence (and up to 6-7 days after). The most effective fungicides are Caramba, Miravis Ace and Prosaro.

--Andrew Friskop, Cereal Extension Pathologist, NDSU Department of Plant Pathology

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org

Most winter wheat fields and nearly all winter barley fields in New York are now past flowering stages and beyond the period for effective fungicide application. There was a predicted, medium to high risk of FHB infection of susceptible winter cereal varieties that flowered in early June in certain areas of the state. Growers are advised to scout their crops over the next few weeks (ideally at kernel soft dough stages) for symptoms of Fusarium head blight in order to assess the likelihood of deoxynivalenol contamination in grain and to plan their harvest strategies and post-harvest marketing of grain. Foliar diseases generally have occurred at minor severities to date. Stripe rust has not been observed beyond individual wheat fields in Seneca and Wayne Counties.

Spring malting barley is progressing rapidly through growth stages with many fields approaching flag leaf emergence, and some fields of ‘Conlon’ barley in the Hudson Valley already emerging from the boot. Spring barley growers are urged to track growth stage closely and to consider a spray with Caramba, Prosaro, or Miravis Ace as soon as most heads are fully emerged (up to 7 days beyond head emergence if necessary). Application of these fungicide products should be based on Fusarium head blight (FHB) risk as well as the risks of powdery mildew, rusts, and fungal leaf blotches in the upper canopy based on scouting of individual fields. Low levels of barley leaf rust have been observed in winter barley and could be a bigger factor in spring barley if moist, humid conditions occur over the next few weeks. Fungicide products containing QoI (FRAC Group 11) fungicides should not be applied to headed barley as they may result in increased levels of DON in grain. Check the Fusarium Risk Assessment Tool (http://www.wheatscab.psu.edu/ ) and your local weather forecast frequently through the head emergence period for spring cereals.

-- Gary Bergstrom, Extension Plant Pathologist, Cornell University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org