24 hour Risk for Fusarium Head Blight development on susceptible wheat varieties (eg Shirley) for May 9, 2018.
Wheat growers in Maryland have so far been fortunate this year for having
low disease pressure from leaf rust, powdery mildew and even scab!! In the
south (Eastern shore), wheat is flowering currently. With consistently
warmer temperatures now, a few incidences of leaf diseases are being
observed. Triazole fungicides: Prosaro/ Caramba/ Proline that are the scab
fungicides should provide control against these as well. Strobilurin
containing fungicides should not be sprayed at this stage, as they may lead
to DON accumulation in grains. Up in the north, flag leaves are emerging. No
diseases being seen so far here as well. Growers should keep an eye on the FHB risk, as crop heads and flowers here in coming weeks.
–Nidhi Rawat, Small grains Pathologist, University of Maryland
By Andrew Kness, Agriculture Extension Educator University of Maryland Extension, Harford County
Figure 1. Wheat head with Fusarium head blight, which causes the premature dry-down and bleaching of florets. Image: A. Kness, University of Maryland
As wheat begins to head, growers will be considering fungicide applications for managing head scab/Fusarium head blight (FHB). The Fusarium Risk Assessment Tool (www.wheatscab.psu.edu) is a forecasting model that predicts your risk for developing FHB on your wheat based on the current and predicted weather forecasts. FHB infection is favored by wet weather and high humidity. You should use this tool to help assess your risk for developing FHB as your wheat approaches flowering. Historically, this tool has been about 70% accurate.
Management of FHB should start with seed selection, since fungicides can only achieve about 50% control under the best case scenario; so selecting resistant varieties is crucial for harvesting good quality grain. It should be noted that resistance to FHB in wheat is not complete; therefore, fungicide applications are often needed in order to achieve acceptable management of FHB and suppression of DON vomitoxin. The pathogen that causes FHB can only infect the plant through the flower, so fungicide applications should be targeted between early flowering (Feekes 10.5.1) and 5 days thereafter. Fungicides that are effective on FHB include the triazoles (FRAC group 3 fungicides), which are Caramba (metconazole), Proline (prothioconazole), and Prosaro (prothioconazole + tebuconazole). These fungicides will also do an excellent job on foliar diseases as well, helping to keep the flag leaf clean. Folicur (tebuconazole) is less effective, but provides some suppression of FHB and DON accumulation, but should not be used if FHB risk is high. Over the past few years, Tilt (propiconazole), has become less effective for managing FHB, and is currently providing poor control. Fungicides containing strobilurins (Qoi, FRAC group 11 fungicides and mix-mode of action fungicides) should not be used past flag leaf emergence on wheat because these fungicides can increase DON vomitoxin accumulation in the grain. For barley, fungicide applications should be made at head emergence. Unlike wheat, barley has no resistance to FHB, so if we get a highly favorable year for FHB development, the very best control you can hope to achieve of FHB and DON is about 50% suppression.
24 hour Risk for Fusarium Head Blight development on susceptible wheat varieties (eg Shirley) for April 20, 2018.
Wheat in southern Maryland is either at jointing or booting stage, and
should be heading out in a week or so. Even with the recent showers, the FHB
risk is currently predicted to be low because of the cold temperatures so
far. However, the temperatures are going to increase by next week, so
growers are advised to keep an eye on the FHB risk forecasts. Up in the
north in Frederick, Harford and nearby counties, plants are starting to
joint, and are not at a stage prone for FHB.
–Nidhi Rawat, Small grains Pathologist, University of Maryland
