Bird cherry oat aphid populations have virtually exploded in many area fields. This has been a recent development, as there were very few aphids observed as late as the end of last month. These aphids are usually considered minor pests that are kept under damaging levels by beneficial insects (parasitic wasps, ladybeetles, and lacewings). But I have seen populations in excess of 1,000 aphids per foot of row this week, causing visible plant stunting. The wheat plants can tolerate many of these insects at this late growth stage, but when the aphid populations expand in large numbers up the leaves, leaving a slick coating of sticky honeydew, a spray threshold has been reached.

I still believe most acreage in the region will not need to be treated. Parasites and predators will become more active in these warmer conditions. Look for evidence of parasitic wasps (aphid mummies), ladybeetles and lacewings. As these beneficials become more abundant, aphid population growth will be curbed in many fields.

Another detrimental aspect of bird cherry oat aphids is that they are vectors of Barley Yellow Dwarf Virus (BYD). However, spring infections of BYD are not as damaging as fall infections. Even if these aphids are harboring the virus, an infection at this late date will probably not cause much damage to the wheat plants. Many growers treated their seed last fall with Gaucho or Cruiser but these treatments have all played out at this point.