INVESTIGATIONS INTO THE ECOLOGY OF THE WHEAT DWARF VIRUS (WDV)IN SAXONY-ANHALT, GERMANY /BINARI MANURUNG

The Wheat dwarf virus (WDV) is widespread in Saxony-Anhalt, Germany. The barley strain was foundin barley, oats, maize and in different species of grasses, the wheat strain in wheat. In triticale, bothstrains were detected. While in the past WDV incidence increased mainly in winter barley, it nowattacks also early sown winter wheat and triticale. Self-sown cereals and grasses serve as infectionsources. Bromus arvensis L., B. commutatus Schrader, B. hordeaceus L., B. japonicus Thunb. ex Murray,B. sterilis L. and Phalaris arundinacea L. have been identified as new host plants of WDV. Individualsof Psammotettix alienus Dahlb. are able to transmit WDV in all stages of their development, but thetransmission mode is subject to very broad fluctuations. Virus acquisition by individuals reached50.0 % in the L2-stage, 45.0 % in L3-stage, 42.9 % in L1-stage, 40.5 % in the imago-stage, 23.6 % inL4-stage and 9.1 % in the L5-stage. The percentage of viruliferous P. alienus in a field populationvaried in dependence on the time of year (June: about 80.0 %; July to October: about 10.0–25.0 %;November to December: about 40.0 %). In single cases, a leafhopper may host both strains of WDV