With rain and warm temperatures in the forecast, risk to scab is moderate in headed and flowering wheat; however, farmers are probably trying to decide whether or not to put anymore money in the crop after the freeze on Sunday/Monday. Lots of wheat in the state was at boot or later and temperatures got down in the upper 20s across wheat areas. We will know the extent of the damage in the coming week or two.

--Trey Price, Associate Professor, Agronomic Crop Pathology, LSU AgCenter

As of March 6, 2023, wheat is at flag leaf emergence and /or early boot stage in some areas of South Georgia, which is ahead compared to other growing seasons. Early incidences of leaf rust have been documented. The FHB risk forecast tool is currently showing medium risk (with spotty high risk) in the Southwest part of the state. Remain vigilant as the crop will soon reach critical stages for FHB infection in this main wheat producing area of the state. For the northwest part of the state, growth stage is at/or nearing stem elongation.

--Alfredo Martinez-Espinoza, Professor and Extension Specialist , University of Georgia

Although the map shows moderate risk at the moment, the majority of our crop is not flowering. Weather does not look conducive for scab over the next several days. Wheat stages in most varieties range from jointing to boot with a few heading in the southernmost part of the state. The condition of the crop is fair to good. We have seen a lot of herbicide and fertilizer injury up to this point…no rust yet.

--Trey Price, Associate Professor, Agronomic Crop Pathology, LSU AgCenter

The Fusarium Head Blight Prediction Center is active for the 2023 growing season. These tools provide daily estimates of disease risk for wheat and barley in 35 states. The risk map is currently showing areas of moderate and high risk in the Southern US. Growers in these areas should consult with local University Extension or other advisors to evaluate the need for fungicide applications.

Tips of using the tool: The tool shows the disease risk for susceptible wheat varieties for todays date. You can select earlier assessment dates by clicking on the calendar menu at the top of the risk map. Use the menu button on the upper left to active risk maps for wheat varieties with other levels of genetic resistance to Fusarium head blight.

Risk maps based on 2, 4 or 6 days of forecasted weather can help users anticipate future trends in disease risk. These maps are available by selecting the 2d, 4d and 6d buttons to the right of the calendar menu.

--Erick DeWolf, Plant Pathologist, Kansas State University

Scab risk remains moderate to high for several areas of the state. The areas of greatest concern are east of the Missouri River, northwest ND, and northeast ND. Sporadic rain storms and long dew periods will likely keep risk elevated for the northern third of ND.

--Andrew Friskop, Associate Professor and Cereal Extension Pathologist, North Dakota State University

This past week's hot and humid weather continues to be forecasted for the next five to seven days. Both the National FHB Risk model as well as the NDSU Small Grain Disease Forecasting Model are, and will likely continue, to indicate moderate to high risk for for spring wheat varieties that are rated as very susceptible and susceptible to Fusarium head blight varieties and moderate risk for the spring wheat varieties that are rated as moderately susceptible and moderately resistant across Minnesota and eastern North Dakota.

Meanwhile, there are a few confirmed reports of leaf rust in wheat and crown rust in oats. I suspect that most oat cares are past the window of a fungicide application. If, however, you find your combine turn an orange/brown color during harvest a fungicide would have been an input with a high return in investment. And while hindsight might be the rear end of a cow, remember it for next year's oat crop.

Bacterial leaf streak (BLS) is starting to show in barley and wheat. The easiest way to confirm BLS is to look for the disease when there is still dew on the leaves. If you suspect BLS lesions, simply out your finger behind the leaf and pull the leaf over your finger BLS lesions will almost be transparent and you can see your finger through the leaf tissue. Understand that fungicides do not control BLS and that you can find BLS in field treated with a fungicide.

Finally, a fourth flight if armyworm into NW Minnesota was reported by Dave Grafstrom at the Magnusson Research Farm near Roseau. With the recent storms there is now plenty of lodged grain that would be very attractive to armyworms. If you see feeding on leaves, check not just for grasshoppers and armyworms, especially in those areas that have lodged.

--Jochum Wiersma, Small Grains Specialist, University of Minnesota

Andrew Friskop, Extension Plant Pathologist at NDSU, shared my concern that the risk models were underestimating the risk of FHB last week. Since the weekend the models have started to trend towards moderate to high risk across much of North Dakota and Northwest Minnesota. Below are his thoughts and my two cents about the current risk situation, a summary of the efficacy of the different fungicides, and some thoughts about if and when to spray fungicides in lodged grain.

Risk Models: This past weekend’s weather for most of the state presented conditions of high humidity, rain, and prolonged dews. These three factors greatly contribute to scab risk and now an elevated scab risk exists for small grains (click here to see the most recent maps). According to the NDSU Small Grain Disease Forecasting Model, the greatest scab risk exists for spring wheat varieties that are rated as very susceptible and susceptible to Fusarium head blight varieties. This includes varieties like AP Murdock, SY Longmire, WB 9479, and WB9590. However, there is still a moderate risk for the spring wheat varieties that are rated as moderately susceptible and moderately resistant in parts of North Dakota (and Minnesota).

When looking at the immediate forecast, high humidity levels will be sporadic amongst the days, yet prolonged morning dews are still likely to occur at least a couple times this week. Given this past weekend’s weather and the forecast, scab risk will likely remain elevated for this week.

Fungicide Efficacy: There are several labeled fungicides that provide *good* scab suppression of scab. These include Caramba®, Proline®, Prosaro®, Prosaro Pro®, Miravis Ace®, and Sphaerex®. Fungicides with the sole active ingredient of tebuconazole are rated as *fair*. The active ingredient propiconazole has *poor* efficacy on scab. To put this in terms of percentage reduction of scab and deoxynivalenol (DON/VOM), *good* fungicides provide about 45-60% suppression, *fair* fungicides may only offer 20-25% suppression, and *poor* fungicides provide only about 10% suppression. Understand that tank mixing fungicides does not mean that the efficacy of the tank mix is the sum of both products. In other words, adding tebuconazole to Caramba does not increase the level suppression of scab to 80% or more. Finally, remember that the premixes that do contain tebuconazole are to create a product that provides good to excellent control of other fungal pathogens, including tan spot an d leaf rust.

--Jochum Wiersma, Small Grains Specialist, University of Minnesota

Fusarium head blight (scab) risk has increased for very susceptible and susceptible varieties in North Dakota. Higher humidity and sporadic thunderstorms are predicted for most of the state this weekend and will likely increase scab risk in most areas. Also, fog and extended dew periods (into the early afternoon) have been frequently reported by agricultural professionals over the past couple days, thus scab concerns have increased for fully-head barley and flowering wheat. Continue to monitor the weather this weekend and start estimating growth stages in small grain fields. We will see an increase in fungicide activity (and decisions) for scab management next week. However, given the large variation in growth stages, we will see an extended season for fungicide decisions for scab.

--Andrew Friskop, Associate Professor and Cereal Extension Pathologist, North Dakota State University

As temperatures and relative humidity values are creeping up so are the hours of leaf wetness and with that the risk for fungal infections. Since last Saturday about two-thirds to three-quarters of the days were favorable for tan spot to develop and about half the days were favorable for leaf rust and Septoria spot blotch. The latter two diseases like it a little warmer than tan spot does. Surprisingly both the National Fusarium Risk Tool as well as the NDAWN Small Grains Disease Forecast model for FHB continue to indicate a low risk of initial infections of Fusarium head blight. There are a few locations in the NDAWN system, however, where the model indicates moderate risk for Fusarium Head Blight. Greenbush, MN, is one of those locations.

Both models share the same origins and rely in a sense on the same framework of sufficiently high enough relative humidities for at least seven days preceding the current day. The higher relative humidity triggers the development of ascospores that subsequently can infect the crop during the most critical period of the wheat development - anthesis and the first week of grainfill.

While rain events are not directly in the model they are in many ways a prerequisite to creating these higher relative humidities. There in lie two possible sources of error in the models' accuracy. Rain events in Minnesota and North Dakota are often very localized with lots of 'have' and 'have nots' over very short distances. That means that the relative humidity in your fields might be much higher than the models indicate. The second weakness is that our soils have lots of organic matter and tremendous water holding capacity, even near the surface. Add to this the fact that the wheat will use water to cool itself by evaporating it during periods of the day that are too warm for the plant to function optimally. With daytime highs in the mid-eighties, the crop uses about a quarter of an inch of water per day. Most of that will end up as water vapor in the canopy. This in turn means that the microclimate in the canopy can be more favorable for ascospore development than is suggeste d by the recorded relative humidity of a nearby weather station.

Bottom line - I am more nervous about the risk of FHB infections than the NDAWN FHB risk model and the National Risk Tool currently indicate. The immediate weather forecast continues to allow for extended leaf wetness periods in a temperature range that favors fungal diseases, including FHB, to develop.

--Jochum Wiersma, Small Grains Specialist, University of Minnesota

The growth stages for small grains in North Dakota is highly variable ranging from early-tillering to flowering stages. The models indicate FHB risk is low for susceptible varieties, and high for very susceptible varieties (uncommon for hard red spring wheat varieties). The state continues to receive sporadic thunderstorms, and the next seven days have high chances of prolonged nighttime/morning dews. Spring wheat and spring barley that will be heading and flowering in the next 7 to 10 days will likely see an increase in FHB risk given these weather conditions. Continue to monitor growth stages in small grain fields and make timely applications in spring wheat (early-flowering and up to 7 days later) and spring barley (full-head and up to 7 days later).

--Andrew Friskop, Associate Professor and Cereal Extension Pathologist, North Dakota State University