INVESTIGATIONS ON THE DAMAGE POTENTIAL OF CEREAL APHIDS (METOPOLOPHIUM-DIRHODUM [WLK], SITOBION-AVENAE [F]) IN A WINTER-WHEAT

Investigations on the damage potential of cereal ahpids (Metopolophium dirhodum [Wlk.], Sitobion avenae [F.]) in a inter wheat: The damage p otential of the cereal aphids. S. avenae and M. dirhodum was investiga ted in winter wheat. Ears and flagleafs were artificially infested wit h different aphid densities between EC 65 and EC 83 using ear- and fla gleaf cages. The aphid densities were adjusted to the initial densitie s every third day. Aphid damage is related to density and duration of infestation. Therefore the aphid infestation was quantified in terms o f aphid days per ear or flagleaf. Yield was measured by calculating dr ymass, thousand kernel weight (TKW), kernals per ear and nitrogen cont ent. The results show that S. avenae at the ear caused significant hig her reduction in drymass and TKW compared to M. dirhodum on the flagle af. Based on the relationship between aphid infestation and yield (dry mass and TKW), the damage factor for S. avenae on the ear was 1.7 time s (drymass) and 2 times (TKW) higher compared to M. dirhodum on the fl agleaf. There was no clear relationship between aphid infestation and the relative nitrogen content.