Putnam County has received roughly 8 inches of rainfall since the beginning of April, nearly 2.5 inches more than normal for this time of year. The timing and abundance of rainfall caused delayed fieldwork, considerable ponding in fields and some replanting. With more rain in the forecast for the week ahead, many are wondering if Fusarium Head Blight (FHB), more commonly known as head scab, will be a concern for the local wheat crop.
Head scab is a fungal disease that reduces yield and quality of grain. The fungus infects flowering wheat heads and can produce vomitoxin, a mycotoxin that contaminates the grain and reduces its marketability. The majority of wheat in our area has flowered or will continue to flower over the next few weeks.
Dr. Pierce Paul, OSU’s specialist in cereal crop diseases, weighed in on the potential for wheat in NW Ohio to develop head scab over the coming weeks and provided the following recommendations. The FHB forecasting system (http://www.wheatscab.psu.edu/) predicts the risk of scab by using the average relative humidity during the 15 days immediately before flowering. If 11-13 days during that 15-day window are cool and dry, then the overall risk will be low, even if it is wet and humid the remaining days. The risk for scab is low in northern Ohio for fields flowering at this time because conditions were relatively cool and dry last week, which likely reduced the risk of the scab fungus infecting wheat spikes. However, farmers should monitor the weather and forecasting system over the next week. Fields flowering at the end of this week through May 30 may be at risk for scab.
Other late-season foliar diseases on wheat have increased over the last week, including strip rust and Septoria. Scout flowering fields to see if your variety is susceptible to stripe rust, Septoria, or even Stagonospora. These disease develop under the cool, wet conditions we have experienced over the last two weeks. Strip rust is localized and restricted to a few varieties but could spread and affect grain yield and test weight in those varieties.
Dr. Paul recommends Prosaro and Caramba fungicides for excellent head scab, rust and Septoria control. Strobilurin fungicides should not be used when the risk for head scab is high because they have been linked to higher vomitoxin levels in the grain. Farmers should also take note of the pre-harvest intervals on any late-season fungicide application. The pre-harvest interval is 30 days for both of these products, so applications need to be made at least 30 days before you begin cutting wheat. It is likely too late to treat fields that are well into grain-fill.
Additional resources on head scab, wheat rust, and guidelines on how to use and interpret the scab forecasting system can be found at http://ohioline.osu.edu. To keep up with the many issues and developments related to agronomic crops across Ohio, subscribe to the OSU Crop Observation and Recommendation Network (C.O.R.N.) newsletter published weekly during the growing season. Go to https://agcrops.osu.edu/newsletter/corn-newsletter and enter your email to subscribe, or contact the extension office and we can subscribe you as well. For more information, contact the Putnam County Extension office at 419-523-6294, by email at firstname.lastname@example.org, or stop in at 1206 East Second Street in Ottawa. You can also find us on Facebook by searching for OSU Extension Putnam County.