S14 - Session P4 - Possibilities for reducing pesticides by single-row covering in apple orchards

Authors: Michael Zoth *, Dominikus Kittemann, Franziska Reinhard

Agriculture is facing with the challenge of enhancing efficient strategies and cultivation methods while taking into account economic, ecological and product-related criteria. This is also due to an increasing consumer demand for residue-free food, stricter residue requirements from trading companies and also by changing legal framework conditions. At the Schlachters research station for pomiculture (Weihenstephan-Triesdorf University of Applied Sciences), experiments were performed within a three years project, aiming to reduce pesticide residues by a reduction in the application of fungicides. A single row covering system, with plastic sheets (2 meters width) sewn on a hail net and under which no fungicides were applied, was compared with a conventional hail net covering, under which standard pesticide applications were realized. No irrigation was installed in order to save costs by using natural precipitation between the rows. The experiments took place in a 'Gala' (IP) and an organic 'Topaz' orchard. Data on infections with fungal diseases, the duration of leaf wetness, the distribution of precipitation in the orchard, the soil moisture content, the generative and vegetative growth as well as yield and fruit quality before and after storage were collected. Results show, that reducing fungicide application under foil cover is possible while maintaining fruit quality. There were less fungal damages before and after storage on the fruit and less fruit russetting due to cold temperatures, compared to the trees under hail net. The risk of mildew infection has to be observed. Young plants should receive supplementary irrigation as the root system is not sufficiently developed to absorb rainwater from outside the tree row. Without fungicide application, there were no residues of fungicides. Nevertheless, more residues from insecticides could be detected. This may be due to the combination of lower uv-radiation and no wash off by natural precipitation under the foil cover.