Scattered areas within Pennsylvania are now at “Medium” risk for the development of scab in wheat and barley that is currently flowering.
Our current weather forecast includes a stretch of wet, mild weather that is conducive to the production and spread of spores. As the week progresses, many areas of the state will likely reach the “High” level for risk. Be prepared to spray a fungicide on fields that are at medium to high risk at flowering.
Remember, sprays applied PRIOR to flowering will NOT provide significant suppression of scab or toxin production.
Caramba mixed with a tebuconazole product, Proline or Prosaro would be effective on scab and give control of some leaf diseases and glume blotch. 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.
Do not use any of the strobilurins (Quadris, Headline), or strobilurin/triazole (Twinline, Quilt, Stratego) combination products at flowering or later. There is evidence they may cause an increase in mycotoxin production.
Here is a chart to help tease out the best fungicide depending on what other diseases may be present in a given field: http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/OFCDwheatfungicides.pdf.
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 percent reduction in scab severity and vomitoxin. A combination of choosing resistant wheat varieties, avoiding planting into corn or small grain stubble and residue management are also required to combat this problem long-term.
Keeping an eye on the FHB Risk Assessment Tool will become critical for those farmers who have wheat beginning to flower late this week and into the next two weeks. This forecasting site, at http://www.wheatscab.psu.edu/riskTool_2011.html, is an online model that helps us predict infection risk levels everywhere in the state.
Visit it at your convenience, or sign up to have updates e-mailed or texted directly to you. The maps on this site update at approximately 10:15am daily, so check back if you receive a “No Data” message.