The Hessian fly-safe date is not only about Hessian fly

By Pierce Paul, Ron Hammond, Ohio State University Extension

For years, a very standard recommendation for profitable wheat production in Ohio has been to plant wheat after the Hessian fly-safe date. This recommendation is based on the fact that at the dates indicated on the map, Hessian fly adults would no longer be alive.   Adults emerge in later summer, mate, and then oviposit in different types of grasses.   Adult life span is extremely short, perhaps only a week, during which time they do not even feed.  After this short time span, adults die off.   The fly-free date is set at a time when it is expected that the adults have died and are no longer around the area.  As a result, damage caused by this insect will likely much less if wheat if planted after the specific date fly-free date in your area.

However, in Ohio the Hessian fly-safe date is not only about the Hessian fly. Anxious to take advantage of early soybean harvest and good planting conditions, some producers have already planted wheat or are thinking about doing so before the Hessian fly-safe date. Some argue that they have not seen the Hessian fly in years, so there is no need to worry about planting after the fly-safe date. However, 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.