STUDIES ON BIOLOGY AND POPULATION DYNAMICS OF THE LEAFHOPPERPSAMMOTETTIX ALIENUS DAHLB. (HOMOPTERA: AUCHENORRHYNCHA) ASVECTOR OF WHEAT DWARF VIRUS (WDV) IN SAXONY-ANHALT, GERMANY / BINARI MANURUNG

Embryonic and nymph (larval) developments of the leafhopper Psammotettix alienus Dahlb. werestudied on winter barley (Hordeum vulgare L.) under laboratory conditions (at 20 °C, 70–95 % RHand 18L/6D). Its population dynamics have been observed on winter barley in field since 1999. In thefield, leafhoppers were caught with sweep-net and biocoenometer with aspirator from May to Novem-ber in 1999 and from April to December in 2000. Under the light microscope, seven stages ofembryonic development can be distinguished. The nymph development consists of five instars. Theduration of embryonic development was 18.3 days (range 16 ... 24 days), whereas nymph developmentlasted 32.4 days (range 26 ... 39 days). In this case, average duration of 1st instar, 2nd instar, 3rd instar,4th instar and 5th instars were 5.9 days, 5.1 days, 5.6 days, 6.3 days and 9.4 days, respectively. In 1999,imago (adult) leafhoppers could be observed in the field from the end of May to the second week ofNovember, while in 2000, they were recorded from the second week of May until the third week ofDecember. That means, the occurrence of leafhoppers as well as their activities as a vector of Wheatdwarf virus (WDV) in cereal crops in the region Saxony-Anhalt was earlier and longer in 2000compared to 1999. In 1999 and in 2000, the peak population density was reached in a self-sown winterbarley (stubble) field in mid-September with 43 and 25 individuals per m², respectively.