Barley yellow dwarf (BYD) disease is one of the most severe viral diseases in autumn sown cereals. In Western Europe, crop losses are mainly due to the PAV species of BYD viruses transmitted by Rhopalosiphum padi, the most abundant aphid in autumn. The proportion of migrant winged aphids that carry viruses in autumn is considered a major epidemiological factor for determining the disease incidence. In the main French cereal areas, during a 6-week period in autumn 1999-2002, the proportion of viruliferous R. padi assessed using a TAS-ELISA technique was on average of 4.98% (range 2.01-9.91%). Variations according to trap location were correlated with land use at the regional scale, annual variations being correlated with the climate of the year. Implementations of these results to improve BYD disease management program are discussed.