Economic populations of this aphid have been found in a few SW Missouri wheat fields. Most of the infested fields were late planted with plants not yet exhibiting head emergence. Most fields in this region of the state do not support economic infestations of this aphid as ladybird beetles and other beneficial pathogens are active and helping to reduce numbers of bird cherry-oat aphids. Although there is much controversy as to the impact this specific aphid has on wheat plants, it is known that the bird cherry-oat aphid is an efficient vector of barley yellow dwarf virus during the fall of the year and does suck plant juices from wheat plants during fall, winter, and spring if present in wheat fields. A review of this aphid finds that numerous thresholds and thoughts about their damage potential to wheat vary greatly from state to state. Past work in Missouri and studies ongoing in more Western states do show this insect can be an important pest of wheat under certain conditions. In the last cropPest newsletter the economic threshold for the bird cherry-oat aphid was listed at 12 to 25 aphids per tiller. Although some states do use this threshold, in Missouri trials conducted several years ago suggested that a more conservative threshold be used due to a greater risk of this pest in the state. Thus, the 2011 economic threshold for bird cherry-oat aphid in Missouri wheat is 12 to 25 aphids present per linear foot of row from emergence in the fall up to initiation of wheat head emergence in the spring. In support of this threshold, some western states are now calling additional research concerning the impact feeding (sucking of plant juices) by the bird cherry-oat aphid has on wheat during spring, winter, and spring seasons. At present, many entomologist believe this pest probably causes more damage to wheat than reflected in traditional economic thresholds.
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REVISED: December 1, 2011