Virus diseases affect legumes sporadically in the Palouse region of Eastern Washington State and adjoining Idaho. In prior years the severity of this disease pressure is not clearly related to the occurrence of the aphids that vector the viruses. Evidently aphid populatins colonizing the crop differ among locations and years in the frequency with which they carry the virus. Producers currently treat all aphids aggressively as if they were vectors, but this may not be necessary. This proposal seeks to measure virus in aphids as they immigrate into the crop in the spring and use this information to develop a virus risk assesment tool for use by producers. The amount of insecticide used to manage virus could thereby be reduced.