Detection of cereal viruses and study of aphid population in Bulgaria.
The presence of viruses and aphid vectors in wheat and barley grown in experimental fields of the State Commission for Cultivar Assessment and the Bulgarian Ministry of Agriculture was studied. Five viruses that are new for Bulgaria were recorded (barley mild mosaic virus, barley yellow mosaic virus, brome streak mosaic virus, cereal dwarf virus and wheat dwarf virus). Spring barley samples gave positive results for the presence of brome mosaic virus, barley stripe mosaic virus and wheat streak mosaic virus. Agropyron mosaic virus, brome mosaic virus and brome streak mosaic virus were detected in wheat. In autumn 1996, Rhopalosiphum padi, R. maidis, Sitobion avenae and Schizaphis graminum were found in winter barley. Sitobion avenae and Schizaphis graminum were observed in wheat. During the spring-summer period, 7 aphid species were recorded for wheat and spring barley (Metopolophium dirhodum, M. festucae, R. maidis, R. padi, Schizaphis graminum, Sitobion avenae and Sipha maydis), 5 of which (M. dirhodum, R. maidis, R. padi, Sitobion avenae and Schizaphis graminum) are known vectors of barley yellow dwarf virus. Sitobion avenae recorded the highest density in wheat (54.4%) and spring barley (52%).