Idaho                                                                             Aphid                                               Flyer

 Cereal Aphids

    Bird cherry-oat aphid numbers are rising in Burley, Aberdeen, Arbon, Soda Springs, And Tetonia. Barley yellow dwarf virus is transmitted by cereal aphids (principally bird cherry oat aphid and, in the southeast Idaho high country, the greenbug). Barley yellow dwarf virus can cause 50-75% crop loss if all the plants become infected. More importantly, we use these aphid numbers as an indicator of the presence of wheat curl mites, which spread wheat streak mosaic virus. This problem seems to occur with higher bird cherry oat aphid populations. The earlier than normal harvest this year, tends to have thoughts running towards earlier than normal fall planting. This is especially true if we get some much-needed moisture. CAUTION! Aphid numbers are too high to predict a safe planting date without the use of a systemic insecticide. Remember-green bugs and bird cherry oat aphids are both insect vectors of barley yellow dwarf virus. Aphid numbers are also used as an indicator of wheat streak mosaic virus. Cereal crops with high resident populations of bird cherry oat aphids can be significantly damaged by BYDV. It is difficult to recommend an action threshold because the damage depends upon what percentage of the aphids are carrying the virus. This can vary greatly from year to year. Another complicating factor is the fact that symptoms of the disease are sometimes ambiguous and often do not show up until spring. As a rule, dry land wheat will suffer more than irrigated crops. Because of the many factors involved, treatment decisions should be made on a case by case basis.

    English grain aphid collections are beginning to increase in northern Idaho. The threshold for these aphids is 100 per head in the soft dough stage. If irrigation has been shut off treatment is not usually beneficial.

     Rose-grass aphid samples show increased numbers across the state. Rose grass aphids do not inject a toxin as they feed and generally cause very little injury. Since they are easily confused with the more damaging greenbug, care should be taken in identification. If you are not sure of the species, contact your University County Faculty or Entomologist before any sprays are applied.

Funded by the University of Idaho Agricultural Experiment Stations and the Wheat & Barley Commissions.

Samples collected July 13 & 20 , 2001