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

I visited the yield trials near Becker, Le Center, and New Ulm earlier this week. The barley has largely headed and about half the oat and spring wheat varieties have headed. Overall, and not unexpectedly, the spring wheat, barley, and oats are shorter than in most years. The first two yield components - the number of tillers per unit area and the number of spikelets per spike or panicle - are average to above average.

BYDV symptoms on the flag leaves of individual plants could be found in all three locations but the incidence was well below 1%. However, I could not find the vector, most likely English grain aphid or Bird cherry-oat aphid, in the canopy. Neither did I find any leaf, strips, or crown rust. I could find some tan spot in the lower canopy of the spring wheat and the start of net blotch on Pinnacle barley.

The risk models continue to show a relatively low risk of initial infections of leaf rust and the Septoria species and a moderate risk of tan spot across the state. The drier conditions in the south and the lower relative humidities across the whole state do not create enough leaf wetness periods at the right temperatures to allow infections to occur. Likewise, the risk of initial infections of Fusarium head blight remains low as well (despite my expectation that it was likely to increase this past week).

Enjoy your 4th of July weekend. A lot of the spring wheat seeded in the second week of May will reach anthesis next week. I plan to increase this small grains disease and pest update twice weekly starting next Tuesday. The immediate forecast looks very favorable for both the crop and the risk of Fusarium head blight as lower relative humidities continue to be forecasted. Nevertheless, I encourage you to ready your sprayers to spray fungicides at Feekes 10.51 as it feels like the weather forecasts have been erroneous more often lately.

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

This weekend's record-breaking heat stalled the risk of initial infections of most all of the foliar fungal pathogens and Fusarium Head Blight. As temperatures have dropped from their record highs and a couple of cold fronts have resulted in widespread thunderstorms across the northern half of Minnesota, the risk of initial infections of tan spot and leaf rust is increasing again. A quick check of your pant legs at 10:00 in the morning or 9:00 at night will be very telling - if you end up with wet pant legs you probably are encountering long enough leaf wetness periods for either disease to start. If you find tan spot while scouting for weeds and testing how waterproof your workboots really are, it is a good idea to add half a labeled rate of a fungicide to your weed control program. If you can not find any tan spot, do not add a fungicide and you save yourself some money. Research from NDSU has shown again and again that you will not see a return on your fungicide application if n o disease present at the time of the herbicide application.

I still have not received any reports of stripe and leaf rust in wheat or crown rust in oats. Most of the oats in Souther Minnesota are now between the flag leaf stage and heading. Check your fields for any sign of crown rust in the lower and middle canopy, especially near treelines, river banks, farm yards, or any other place you might find buckthorn. The immediate forecast will be relatively favorable for crown rust just to start, especially in more wooded areas of the state where dews take longer to burn off. Spray a full rate of a labeled fungicide in oats that has a very good or excellent efficacy rating for leaf or stripe rust in wheat and follow label restrictions for oats.

Meanwhile, the first barley fields in southern Minnesota are heading. The risk of Fusarium head blight dwindled with the high temperatures and the lack of widespread rain events across the southern half of teh state. The risk is predicted to wain with the extreme heat that is forecasted.

The optimum timing to suppress scab in barley (and control any leaf diseases that also may be present) remains at Feekes 10.5 (or fully headed). Miravis Ace provides a wider application window as it maintains adequate suppression up to 5 days after Feeks 10.5 compared to the other fungicides labeled for suppression of FHB. Overall, I expect the risk of FHB to start increasing again by this weekend, especially in those fields that did receive some precipitation about a week to 10 days ago or that are under irrigation and received water during that same timeframe. If you grow Pinnacle, I suggest you spray a labeled fungicide regardless as this variety is too susceptible to net blotch to leave unprotected.

Finally, there have been several flights of armyworms into the state, and moths have been caught in suction and pheromone traps from south-central Minnesota all the way up to Roseau and Lake of the Woods counties on the Canadian border. The first armyworm moths were caught over the Memorial Day weekend with additional flights in the following two weekends (I guess they also are 'Going up North to the Lake' during the weekend). Their brood takes some 8 to 10 days to hatch. While the first few instars do not do a lot of feeding damage, the last two instars can do a lot of damage. Scout for armyworm on headlands and lodged grain first. Frass pellets confirm that there are armyworms present as larvae are shy of full sunlight and will hide near crowns and under clumps of soil. The threshold for treating armyworms is 4-5 larvae per square foot.

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

The risk model for tan spot indicates that about half the days this past week have been favorable for initial infections, meaning that the canopy stayed wet long enough and at the right range of temperatures to allow spores to germinate and infect the wheat plants. The risk has been higher further south and east. The forecasted heat will likely halt additional infections and slow down the existing infections. Nevertheless, I encourage you to scout the spring wheat before you do your weed control and determine whether you have tan spot present in your field. If you find tan spot it is a good idea to add half a labeled rate of a fungicide to your weed control program. If you can not find any tan spot, do not add a fungicide and you save yourself some money. Research from NDSU has shown again and again that you will not see a return on your fungicide application if no disease present at the time of the herbicide application. I have not received any reports of stripe and leaf rust in wheat or crown rust in oats as of today. The risk models have indicated low risk and that risk is not expected to increase in the next couple of days.

Meanwhile, winter rye is at anthesis across much of the state, and winter wheat in the southern part of the state is now at anthesis heading. The risk of Fusarium head blight remains highest in the southeastern corner of the state. East of US Hwy 169 from the Iowa border to the Twin Cities is now at moderate risk while the area east of US Hwy 63 is now at moderately high to high risk. The risk is predicted to wain with the extreme heat that is forecasted.

The optimum timing to suppress scab (and control any leaf diseases that also may be present) remains at Feekes 10.51 for winter wheat and rye for all fungicides labeled for use in the respective crops. Miravis Ace provides a wider window of application as it maintains adequate suppression up to 5 days after the beginning of anthesis compared to the other fungicides labeled for suppression of FHB. The decision to use a fungicide in either winter wheat or winter rye has, given the immediate forecast, not become any easier as this extreme heat not only reduces the risk of infections it also creates a lot of stress on the crop, thereby reducing its yield potential.

I received a few reports of aphids in oats in southern Minnesota but none of those fields were at the economic threshold of 80% of the stems having at least one aphid on them prior anytime prior to anthesis. Meanwhile, grasshoppers have emerged in numbers and it is not difficult to find the little nymphs on field edges. Counting these little rascals in front of you to determine whether you are at the economic threshold of 50 to 75 nymphs per square yard is something different altogether. Using a 15-inch sweep net and making four 180-degree sweeps very close through the ground and more or less through the crop gives you a much better estimate of the number of nymphs per square yard.

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

As of June 2, 2022, in the Texas Panhandle (Moore and Sherman counties), wheat are ripening now (Feekes 11). The varieties of the wheat evaluated in farmer’s fields are unknown. General observation is that wheat heads have started to mature and several heads in some of several of the fields evaluated had FHB infections. Like most of the Panhandle area of the state temperatures have been high with conditions remaining dry and hot. About eighty-five percent of the fields evaluated were irrigated.

As of June 6, 2022, in the Texas Panhandle (Potter county), wheat are ripening now (Feekes 11). Wheat variety evaluated are include TAM 114. General observation is that wheat heads have started to mature and a few instances of FHB infection have been identified in the evaluated field. Temperatures in this area of Texas has been high over the past week and currently in the triple digits with little rain. Essentially, conditions have remained dry and hot with occasional high winds.

As of June 6, 2022, in the Texas Panhandle (Dallam and Hartley counties), wheat are ripening now (Feekes 10.5-11). The varieties of the wheat evaluated in farmer’s fields are unknown. General observation is that wheat heads have started to mature and a few number of heads in a few number of the fields (about 30%) evaluated had FHB infections. Again, like most of the Panhandle area of the state temperatures have been high with conditions remaining dry and hot. About eighty-five percent of the fields evaluated were irrigated.

--Ken Obasa, Assistant Professor & Extension Specialist, Texas A&M University

There are some reports of winter wheat starting to show awns and we are likely only a few days away from heading and then flowering. The current scab risk in North Dakota is greatest for susceptible and very susceptible winter wheat varieties in southwest ND. I would expect scab risk to remain elevated for southwest ND in the coming days and we may see other pockets of scab risk appear with recent rain events. Please continue to use the risk model to assess scab risk as winter wheat starts to flower.

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

In Wisconsin, wheat diseases have been nearly non-existent up to this point. Cool weather has generally kept wheat disease at low levels. However, increase frequency of rain events and moderate temperatures over the next 7-10 days will likely increase disease risk, especially Fusarium head blight (FHB or Scab).

We are entering the window for fungicide applications for FHB here in Wisconsin. Currently the Fusarium Head Blight Risk tool is predicting more areas of moderate to high risk in Wisconsin for FHB than it did a week ago. If highly susceptible wheat varieties were planted in Wisconsin, the current risk is high across most of the state. Rainy conditions in the next seven days will likely push this risk higher. Now is the time to consider a fungicide application to manage FHB in Winter wheat in the state.

In winter wheat in Wisconsin, research has demonstrated that the best time to apply fungicides is between the start of anthesis (first anthers out) to 7 days after the start of anthesis. This same research has demonstrated that waiting to apply fungicides 5 days after the start of anthesis, optimizes deoxynivalenol (DON or vomitoxin) reductions in finished wheat. This is due to the fact that head emergence in Wisconsin can be very uneven. Waiting 5 days after the start of anthesis may help with optimizing application timing to maximize heads flowering and receiving fungicide protection. Fungicide choice is also critical, with Prosaro, Caramba, and Miravis Ace providing the most consistent control of Fusarium head blight and reduction of DON in trials in Wisconsin. Fungicides containing strobilurin fungicides should be avoided after the boot stage of wheat as these products can increase DON levels in finished grain.

For more information, please visit my June 1, 2022 update here: https://badgercropdoc.com/2022/06/01/wisconsin-winter-wheat-disease-upd….

--Damon L. Smith, Associate Professor and Extension Specialist, University of Wisconsin-Madison

Head Scab Risk has Increased Across Ohio.

Due largely to rainfall, high relative humidity, and warmer temperatures over the last several days, the risk for head scab is now moderate across most of the state of Ohio, and high across the south. The risk is low in NW Ohio. This would be the time to consider applying a fungicide to control head scab and reduce the risk of grain contamination with mycotoxins as fields reach anthesis in the northern third of the state. Even fields in the lower half of the state that flowered 5-7 days ago could benefit from a fungicide application. Most of the recommended fungicides for FHB management provide similar levels of FHB and vomitoxin suppression when applied between early anthesis (Feekes 10.5.1) and early grain-fill (up to six day after early anthesis).

The recommended, and most effective, fungicides for scab and vomitoxin control are Miravis Ace, Prosaro, Caramba, Proline, Sphaerex, and Prosaro Pro. These products provide comparable levels of scab and vomitoxin suppression when applied at early anthesis or shortly thereafter. Applications made to wheat at early or full head emergence (between Feekes 10.3 and 10.5) may also suppress scab (compared to no fungicide at all), but tend to be considerably less effective against vomitoxin. Several of these fungicides are also very effective against leaf diseases, which are also on the increase in some areas. Please read product labels carefully before making an application, in particular, pay close attention to the preharvest intervals.

--Pierce Anderson Paul, Extension Plant Pathologist, The Ohio State University

Most areas of Central and Southern PA have flowering wheat, or wheat that is about to flower. Scab infection risk is growing across the state for all resistance classes of wheat. If your wheat in these areas is heading and approaching flowering, stay alert and consider a fungicide application. Caramba, Prosaro and Miravis Ace give good control of most leaf and head diseases, in addition to suppressing scab. Spray nozzles should be angled at 30° down from horizontal, toward the grain heads, using forward- and backward mounted nozzles or nozzles with a two directional spray, such as Twinjet nozzles. If weather conditions prevent fungicide application at early flowering, an application as soon as conditions allow will still be quite effective in reducing scab and DON production. Follow labels to determine post-harvest interval constraints for the fungicide you choose.

Continue to visit wheatscab.psu.edu to use the Fusarium Head Blight Prediction Center for estimating your crop’s scab risk.

--Alyssa A. Collins, Associate Professor, Plant Pathology and Environmental Microbiology, The Pennsylvania State University