Commentary, Michigan

Up to a week ago, the usual early season diseases (powdery mildew and Septoria leaf blight) had difficulty making much of a showing due to cool (and cold ) temperatures. Currently however, some disease, particularly powdery mildew, is being found on susceptible varieties across much of the state. Where disease pressure is low to moderate, growers who are inclined to use a fungicide are encouraged to consider postponing the applications until early flower so that both fusarium head scab and leaf diseases can potentially be addressed in a single fungicide application. However, if the scab model continues to indicate a low risk, growers might still find leaf diseases severe and warrant treatment. In this case, consider a moderate rate of Prosaro, Caramba or tebuconazole between the boot and early flowering stages.

–Martin Nagelkirk, MSU Extension Educator, Michigan State University

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

The risk of scab has dropped back to the low level. Most wheat in the state has flowered and the remaining late-planted fields in the northern part of the state should finish flowering this week. A large portion of the crop should have little or no scab this season. It is advisable, particularly in areas where scab risk was forecast to be high, to scout fields just before the crop turns to determine the extent of infection. Scab infested fields should be combined with a high fan speed to reduce the number of heavily infected seed. This will reduce the vomitoxin level in the harvested grain as well as improve test weight.

–Arv Grybauskas, Extension Plant Pathologist, University of Maryland

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Due to the dry weather, there is very little FHB in KY this year. Wheat in west Kentucky is now beginning to turn and is mostly at the soft dough stage or later.

–Don Hershman, Extension Plant Pathologist, University of Kentucky

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

The 2012 prediction tools provide daily estimates of risk for Fusarium head blight. Selecting a state from the map will zoom view to individual states and detail the risk of disease in that area. The risk maps show current estimates of the risk of Fusarium head blight based on weather past seven days. A green map indicates a low risk of severe disease. Yellow and red colors on the map indicate progressively greater levels of disease risk. Wheat is most vulnerable to infection during anthesis (flowering) and the early stages of grain development. Therefore, the weather conditions preceding these critical growth stages are critical for disease development. Use assessment dates on the calendar (shown on the left of the map) to monitor risk as your wheat moves toward these critical stages of development. Winter wheat in many areas of the country is developing faster than usual. This week the focus is on southern OH, and PA. Some fields in northern IN and IL are likely at vuln
erable growth stages this week.

–Erick De Wolf, Extension Plant Pathologist, Kansas State University

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Most wheat in Kansas is now past the flowering stages of growth that are most vulnerable for infection by Fusarium. Wheat in northwestern KS has been flowering the week of May 7. Wheat in North central KS was flowering the week of April 23. Although there were some rain showers on April 27 and 29, the risk models consistently indicated that conditions were not favorable for serious problems with Fusarium head blight (FHB). Wheat in south central KS is now at the milk and early dough stages of kernel development. To date, I have not observed or heard of fields with FHB in KS.

–Erick De Wolf, Extension Plant Pathologist, Kansas State University

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Winter wheat development in New York ranges from Feekes growth stage 8 (flag leaf just visible) to stage 10 (in boot). Plants currently in boot should begin to flower in the next week or so with daily high temperatures predicted to be in the 70s. Only minor levels of powdery mildew and fungal leaf blotches have been observed in lower wheat canopies and upper leaves are generally free of disease symptoms. No rust has been sighted yet in New York. Note that fungicide products containing strobilurins should not be applied after flag leaves have emerged in order to avoid a risk of elevated levels of the mycotoxin deoxynivalenol (DON). Most New York wheat producers will make a critical decision in the next week on whether to make a single application of triazole fungicide at the onset of flowering (Feekes stage 10.5.1), coinciding with the principal infection period for Fusarium head blight (FHB). The triazole fungicides Caramba, Prosaro, and Proline have shown the greatest
efficacy in suppression of FHB and reducing the potential for mycotoxin contamination in grain. These materials when applied at flowering also provide very good protection against powdery mildew, rust, and fungal leaf blotches during the critical early grain-filling period. We have experienced moist conditions recently that favor production of Fusarium spores on corn and small grain crop residues, but moisture must also be present on wheat heads at flowering for significant infection to occur. It appears that the earliest planted wheat may begin to flower during a fairly dry period, but that forecast could easily change over the next week. Growers are urged to consult the FHB Risk Assessment Tool and State Commentary frequently as their crop approaches flowering.

–Gary Bergstrom, Extension Plant Pathologist, Cornell University

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Wheat in the northern half of Illinois is either already flowering or will be in the next few days. The risk of FHB currently is low for the northern half of Illinois; however, stripe rust is continuing to move northward in the state. Fungicides registered for suppression of FHB that can be applied during the flowering stage of wheat also have efficacy against stripe rust.

–Carl Bradley, Extension Plant Pathologist, University of Illinois

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Maturity of our winter wheat is well ahead of normal and could have some important consequences on crop yield and management this year. Our wheat lines in Centre County have started heading yesterday May 7 compared to May 26 last year and May 15 in 2010. This will likely mean that wheat could benefit from cooler temperatures during the grain fill period, and perhaps and longer grain fill period and higher yields. The disease situation in wheat in Pennsylvania is critical to monitor. Powdery mildew and Stagonospora have been advancing upward in the canopy in our variety trial recently with the cool wet conditions. With the potential high yields in this years crop, it is important to try to keep these diseases off the top two leaves. There are striking differences among varieties for mildew resistance in our trials so if you are seeing heavy mildew infestations, you may want to reevaluate varieties for next year.

Most wheat is heading and/or flowering and is at or approaching the critical stage for treating for head scab or other diseases if the risk is high. The risk for head scab has been low on the FHB Risk Assessment Tool, but today high risk areas began to appear on our map likely due to the warm and wet conditions this week. There is also some risk of a leaf rust infestation as Kentucky and other southern states have reported rust in many fields and some of those spores could have moved here during the last two weather fronts that moved through. I would be monitoring wheat diseases and planning fungicide applications accordingly. Triazole fungicides such as Caramba and Prosaro have the most activity on Fusarium Head Blight when applied at flowering. These products also provide good control of powdery mildew, leaf blotches and rust when applied then for the critical early grain fill period.

–Greg Roth, Extension Agronomist, Pennsylvania State University

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Several hot spots have developed in the last few days, where the forecasting system predicts a high to moderate risk of scab development in Maryland. Most wheat in the high risk regions in the central to southern part of MD should be past flowering. However, there may be a few late planted fields that have just reached flowering. The hot spots in the northern tier, especially in Cecil county should have wheat at or approaching flowering. The areas with a high risk forecast and wheat at flowering should consider a fungicide application. Stripe rust has also been confirmed in Dorchester and Caroline counties. If cool weather persists and frequent dew or rainy conditions develop during grain-fill, stripe rust can reach levels that will cause some low to moderate yield loss on susceptible varieties. Fungicides can only be applied to wheat up to mid-flower. The products registered for scab management, Prosaro and Caramba, are also effective against leaf and stripe rust. Rust susce
ptible wheat varieties that are still eligible for a fungicide application (pre- or just at flower) and are not in a scab high risk forecast area may be sprayed with Folicur or a properly labeled generic tebuconazole product for rust control. Note that Prosaro, Caramba and Folicur have a 30 day Pre-Harvest Interval as well as the growth stage restriction. Tilt has a 45 day PHI, and therefore would only be an option on earlier stage wheat where the risk of scab was low.

–Arv Grybauskas, Extension Plant Pathologist, University of Maryland

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html

Wheat continues to approach and advance through the critical flowering growth stage across the state of Ohio. Several fields are flowering in the southern third of the state, will begin to flower in central Ohio later this week, and in the northern third of the state within the next 7 to 10 days. For wheat flowering early this week, the scab forecasting tool (http://www.wheatscab.psu.edu) indicates that the risk for scab is low. This is probably because it has been fairly dry and cool over the last few weeks. The forecast is for scatted showers and possible thunderstorms tonight (Monday May, 7) and tomorrow, which favors scab, but temperatures are predicted to remain in the 60s and lower 70s for all of this week, with nighttime temperatures in the 40s. This will likely cause the risk of scab to continue being low over the next week or so, but keep checking the weather, the growth stage of your crop, and the scab prediction website to get a better estimate of the scab risk in
your field.

These cool temperatures may mean low scab, extended grain fill, and consequently, high grain yield and quality. However, cool, humid conditions may also mean problems with other diseases such as powdery mildew and Septoria leaf blotch. These diseases have already been reported on the flag leaves in fields with susceptible varieties. Scout fields and plan to apply a fungicide if your variety is susceptible and lesions are already in the leaf below the flag leaf. However, remember that a fungicide applied before flowering will not provide adequate control of head scab if condition do eventually become favorable.

–Pierce Paul, Extension Plant Pathologist, The Ohio State University

For more details, go to the FHB Risk Assessment Tool at http://www.wheatscab.psu.edu/riskTool_2012.html