Plant after the Hessian Fly Safe date for your county. The Hessian Fly free dates can be found at (http://ohioline.osu.edu/iwy/flydates.html). These dates vary between September 22 for northern counties and October 5 for the southern-most counties. Central Ohio counties are right at the end of September of start of October. Planting within the first 10 days after the recommended fly-safe date minimizes the risk of serious problems with Hessian Fly.
This is because on those dates, the weather conditions, especially temperature, are unfavorable for the Hessian fly. As a result, damage caused by this insect will likely be less if wheat is planted after the specific date. However, in Ohio the Hessian fly-safe date is not only about the Hessian fly. 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 has shown 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.