SCOUTING FOR APHIDS IN WINTER WHEAT FIELDS WITH OR WITHOUT INSECTICIDE SEED TREATMENT IN MARCH AND APRIL IS CRITICAL TO REDUCE BYDV

INTRODUCTION Most of the small grain fields in Kentucky are located in the western region. Small grains (i.e. wheat, barley, rye) are planted in this region from October to the end of November after soybean and corn were harvested. Barley yellow dwarf virus (BYDV) is one of the most important pest problems in wheat. If infections occur in earlier stages of plant development yields might be reduced drastically. Barley yellow dwarf viruses are caused by luteoviruses transmitted by several aphid species. At least 25 aphid species are potential vectors of these viruses (Bauske et al. 1997). Most of these species are present in Kentucky however, Rhopalosiphum padi (bird cherry oat aphid) (Figure 1) is the most abundant and common species, followed by Sitobion avenae (English wheat aphid). Furthermore, the most effective vector of BYDV is R. padi (Smith 1963).