Source: Andy Michel, Laura Lindsey, Pierce Paul, OSU
With the autumn rapidly approaching, wheat planting is likely to begin soon. Planting after the Hessian fly free date remains the best chance to avoid issues with insects and diseases, as well as helping ensure good agronomic quality. Some benefits of the fly free date:
Hessian Fly: Adults of the Hessian fly lay eggs in emerging wheat. These eggs then hatch into small larvae that feed before spending the winter as a flaxseed. The early autumn feeding will stress the young wheat plant right before the winter, resulting in stunted and wilted plants. Very little egg laying occurs after the fly free date, which helps to limit infestation. Wheat varieties with resistance against the Hessian are available, in addition to seed treatments, which can help limit damage.
Aphids: Two main aphids infest wheat in Ohio: the English grain aphid and the bird cherry-oat aphid. These aphids rarely cause economic injury on wheat from feeding. However, they can transmit several viruses that can severely impact wheat including Barley Yellow Dwarf virus. These aphids do not only feed on wheat, but several other grasses that serve as natural sources of viruses. If wheat is planted too early, and emerges before the aphids overwinter or stop feeding, they can be early transmitters of viruses. Although seed treatments could help kill the aphids, they may survive long enough to transmit the virus to the plant. Any transmission in the autumn would likely serve as a local source in the following spring.
Other foliar diseases: Although not directly related to the Hessian Fly, planting after the fly free date also helps to reduce the early establishment of leaf diseases like Stagonospora leaf blotch and powdery mildew. Planting date is indirectly linked to spore production by fungi that cause these diseases and infection of young plants. The earlier you plant, the more spores are available, and the more suitable (warmer) conditions are for infection. Fall infections often leads to more damage and greater yield loss in the spring, especially of susceptible varieties are planted and not protected with a fungicide at Feeks 8 (flag leaf emergence). As conditions become cooler after the fly free date, pathogens that cause leaf diseases become last active, and as such, are less likely to infect plants.