By Alyssa Collins and Paul D. Esker
Many barley varieties are heading in the southern parts of PA, and others are not far behind. Disease pressure in our region has been low up to now with cooler temperatures, low humidity, and high winds, but these conditions are changing rapidly with lingering rain showers coupled with warmer temperatures. We should expect to see increased levels of common foliar diseases like powdery mildew and leaf blotches, and a greater threat of Fusarium head blight (a.k.a. head scab). As many of you know, this is a disease of wheat and barley that can lead to the production of vomitoxin (DON) in grains.
If you intend to protect your barley from scab using a foliar fungicide, it is important to be prepared to spray at 50% heading or shortly thereafter. Once your crop begins heading, there is approximately a 5-to-6 day window to apply a fungicide. Current labels state that the last stage of application is mid-flower and there is a 30-day harvest restriction. Do not use any of the strobilurins (Quadris, Headline), or strobilurin/triazole (Twinline, Quilt, Stratego) combination products at flowering or later. There is evidence that they may cause an increase in mycotoxin production.
Caramba, Miravis Ace, and Prosaro all provide very good scab suppression. The Miravis Ace label allows for earlier application than Caramba or Prosaro, but best results are still achieved when application is timed at heading in barley. 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. Additionally, a fungicide treatment at heading using any of these products will also give you excellent control of most leaf diseases as well.
At this point in the season, the only way to reduce the scab problem is to spray. But in general, do not rely solely on fungicides, as they will provide at most a 50–60% reduction in scab severity and vomitoxin. Start with selecting resistant varieties, and time sprays properly to achieve greater control.
As our season progresses, keeping an eye on the FHB Risk Assessment Tool will become critical for those farmers who are trying to make the decision to spray wheat as well. The Wheatscab forecasting site, is an online model that helps us predict infection risk levels everywhere in the state. It continues to undergo major revisions and updates to serve the industry better, so you may notice a different look. Stay tuned to Field Crop News for updates on the new functionality of the FHB Risk Assessment Tool.
If you need a refresher on determining the growth stage of your small grains, view this excellent video by Paul Esker .
Source : psu.edu