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Agronomic Crops Network

Ohio State University Extension


Hessian Fly-free Date: Good for Wheat, Cover Crops and Disease

Hessian Fly-free Date by County

A good rule of thumb for planting wheat is to wait after the Hessian fly-free date.  These dates are predictions on when most Hessian fly adults would no longer be alive and lay eggs in wheat fields.  If planted too early, the eggs can hatch and stunt or kill the wheat plants. Keep in mind that this date is also good for cover crops as well, as mentioned by the Penn St. Field Crop News (  While we may not be so concerned about Hessian fly killing cover crops in the following spring, we do not need to provide Hessian flies with good host material and start building our populations. So the fly-free date works for wheat-for-profit fields as well as wheat for cover crops.

Another excellent reason to plant wheat after the fly-safe date is to minimize problems with diseases, especially barley yellow dwarf virus (BYDV). BYDV is transmitted by aphids and tends to be most severe when transmission occurs in the fall. Research showed that due to unfavorable weather conditions, the aphid population tends to crash after the fly safe date, leading to fewer problems with BYDV. Planting date studies conducted here at OSU a few years ago showed that BYDV problems and yield loss associated with this disease are much higher when wheat is planted well before the fly-safe date. Planting after the fly-safe date also minimizes early establishment of other diseases such as Stagonospora blotch and leaf rust.

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.