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Agronomic Crops Network

Ohio State University Extension


Wheat Disease Update: The Week of May 18 2015

The wheat crop progressed considerably over the last week and is now heading-out in some fields. In fact, some fields in southern Ohio and even fields planted early or with early-maturing varieties in the central and northern parts of the state are at the flowering growth stage or will be flowering by the end of this week. The forecast is for cool conditions and rain over the next few days, which could potentially slow down the development of the crop. Scab and vomitoxin become our biggest concerns at this time of the wheat season. Keep your eyes on the weather and the scab forecasting ( and alert systems, and be prepared to apply a fungicide (Prosaro or Caramba at full label-recommended rates) at flowering. For those early-flowering fields planted with varieties that are very susceptible to scab, the risk for head scab is currently low-moderate and will likely remain low as conditions become cooler over the next three days.

So far this season, conditions have not been very favorable for the development of early-season diseases such as powdery mildew and Septoria. However, the extended cool weather and recent rainfall and high relative humidity could cause that to change. Septoria usually spreads from the lower to the upper leaves during rainy weather and develops best as temperatures between 50 to 68oC. Powdery mildew also develops well under cool conditions with high relative humidity. So monitor fields for powdery mildew and Septoria over the next week, and if lesions are seen on the leaf below the flag leaf, particularly if the variety is susceptible, a fungicide may be needed to prevent the diseases from reaching the flag leaf (the upper-most leaf of the plant) before grain-fill is complete. However, remember, applications made prior to flowering will control leaf diseases, but will not adequately control head scab. 

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.