| Popis: |
Relations between host plants and phenology of the gall midges Contarinia tritici (Kirby) and Sitodiplosis mosellana (Geh.). The phenological differences between C. tritici and S. mosellana are shown under exact conditions in the laboratory. The existance of a second generation of C. tritici could not be confirmed by investigations in the field. Temperature, rain, and soil moisture are influencing the course of the wheat blossom midges flight. The effect of the wheat blossom midges best known host plants, i. e. wheat, rye and couch grass (Agropyrum repens) on the population dynamics of the two species in Germany is examined. Rye is scarcely attacked by S. mosellana in wheat growing areas with a small portion of rye grown in it. But in some areas of the Weser-Ems territory, where only rye is grown, the phenology of S. mosellana has been adapted to the early blossoming of rye, as could be stated by means of rearing in the laboratory. Winter wheat and spring wheat usually are attacked in the same degree by S. mosellana. The midges that emerge when wheat has finished blossoming, oviposit on wheat ears appearing very lately, and on couch grass. The maximum flight of C. tritici is correlated relatively firmly to the time of appearance of the wheat ears. Early varieties of spring wheat do not safely escape the attack by C. tritici. For this midge, too, the wheat ears appearing very lately, and couch grass are a reservoir of host plants. |
