Sel’skokhozyaistvennaya Biologiya [Agricultural Biology], 2013, № 3, p. 117-123 UDC 633.11:(632.3+632.753.1)(470.44/.47) VIRAL DISEASES OF WHEAT AND THEIR MAIN CARRIER IN THE CONDITIONS OF LOWER VOLGA T.S. Markelova, E.A. Baukenova Research and Development Institute of Agriculture of the South-East, RAAS, 7, ul. <...> Tulaikova, Saratov, 410010 Russia e-mail: tsmarkelova@bk.ru, raiser_saratov@mail.ru Received August 28, 2012 S u m m a r y Of numerous diseases of agricultural plants, the viral and mycoplasmal diseases cause the biggest losses. <...> The most widespread wheat viral diseases in lower Volga are the Russian winter wheat mosaic, mosaic of awnless brome, barley yellow dwarf and wheat pale green dwarf, the last one caused by a mycoplasma infection. <...> The large majority of phytopathogenic viruses are distributed by insect vectors, which, as a rule, are virus-specific and often provide not only the transfer of virus particles but also their long-time keeping, multiplication and virulence rising. <...> The presented investigations in 2010-2011 suggested that high amount of leafhoppers, their virus-carrying, and also favorable weather conditions are basic factors for the spreading of viral infection on wheat plants. <...> The dynamics of leafhoppers number was investigated on two winter wheat varieties and two spring ones, the degree of development of complex viral diseases on culture was studied. <...> It was shown that in 2011 significant reduction of carrier population (as compared with 2010) resulted in decrease of prevalence of viral infection both on spring and winter wheat. <...> Both on spring and winter wheat the first symptoms of infection can be already observed at tillering. <...> At the earing phase the majority of infected plants does not form the ear or are lost entirely. <...> Grain production is the main agricultural industry in arid conditions of the Volga region. <...> However, yields of wheat closely depend on the extension of its most significant pathogens – viral diseases and mycoplasmas (1). <...> Viruses can move from one group of cereals to others via seasonal migrations of insect carriers in crop rotations oversaturated with cereal crops (3). <...> Once infected by a virus, a plant becomes its constant carrier with almost no exceptions (3). <...> Insect vectors (7 <...>