Dry and hot spring weather has been keeping scab risk low up to this point, however, some areas are at medium risk this week. While the risk map is very helpful to determine average risk across large areas, it may not always reflect precise conditions that occur in pockets of wheat production that are not well-represented by weather stations. If your wheat or barley has been experiencing showers or high humidity for a few weeks, consider a fungicide application for scab at early flowering. If you plan to spray for head scab, choose a labeled triazole-containing product (FRAC 3) like Proline, Prosaro, Prosaro Pro, Miravis Ace, or Sphaerex. Do not use a product that contains any strobilurin (FRAC 11). The Miravis Ace label allows for earlier application than other fungicides, but best results are still achieved when application is timed after full heading in barley and flowering in wheat. If weather conditions prevent fungicide application at ideal timing, 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. Spray nozzles should be angled at 30 degrees 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.

Given the extreme heat across much of PA early this week, there is increased risk of phytotoxicity (including interference with pollination) as a result of untested tank mixes. Avoid including additives in your fungicide application, such as fertilizers, insecticides and adjuvants while wheat is flowering in these conditions. If a spreader or sticker is recommended, follow the fungicide label to determine the appropriate one.

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