Biological Control of Woolly Apple Aphid (Eriosoma lanigerum HAUSM.) with Aphelinus mali HALD

The release of Aphelinus mali HALD. from artificial rearing for the control of Woolly Apple Aphid (Eriosoma lanigerum HAUSM.) was tested in field trials. The release of adults proved to be more suitable than the release of cards with parasitized mummies as practised in the first trial. Setting free adult A. mali at the beginning of June reduced the aphid population, though its efficiency was not high enough to prevent damage of the trees totally. The practical applications of A. mali in early spring (after blossom) were not effective because climatic conditions were not suitable enough. The fertility of A. mali depends on temperature and light intensity. The application of Micula (rape oil) and T-S forte reduced the growth of the aphid population effectively. These substances may be used in a combined strategy to improve the successful subsequent release of A. mali. Possible phytotoxic effects, however, must be considered in this context.