Investigations in Hesse (FRG) on effects and impact of unsprayed crop edges. 2. Population growth of cereal aphids and their specific antagonists
1988
Kuehner, C. (Biologische Bundesanstalt fuer Land- und Forstwirtschaft, Darmstadt (Germany, F.R.). Inst. fuer Biologische Schaedlingsbekaempfung)
The effect of herbicide- and insecticide-free crop edges on the population dynamics of cereal aphids and their specific antagonists was investigated for the purpose of a coordinated experimental programme. The experiments were carried out at three different locations in Hesse (Giessen, Schluechtern and Darmstadt). In the unsprayed plots in Giessen and Schluechtern with their diverse range of flowering plants the amount of cereal aphids was distinctly lower than in the ones treated with herbicides. At the same time in these locations more predators in relation to parasitoids could be found: especially this is true for the Syrphidae. In contrary, the unsprayed crop edge in Darmstadt was mainly characterized by different species of grass and only few flowering plants. In this plot there was no reduction in the number of aphids compared to the herbicide treated one. Most of the beneficials belonged to the parasitic Hymenoptera. Predators as an important group of aphid antagonists were represented only in small numbers. These results indicate the great importance of an abundant range of plant species in unsprayed edges for the development of different beneficials. The early set up of a widely spread spectrum of beneficials is one important factor in affecting the population dynamics of aphids. Besides their ecological importance unsprayed crop edges could also attain economical significance, which in term should be employed in integrated pest management
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