Abstract
In organic apple growing, yield control is commonly achieved by removing buds and flowers with mechanical thinning machines and/or lime sulphur sprays. To allow for thinning also later in the season, trials with shading nets have been carried out over several years. By shading trees with close-meshed nets before June fruit drop, photosynthesis in the leaves can be drastically reduced. Regardless the good trial results, the method is not used in the field, because shading trees with nets is labour-intensive and expensive. We therefore tested different substances as alternatives to shading nets. First promising results were obtained with different oily substances. However, based on our current knowledge, negative side effects such as leaf burn and fruit russeting, can not be excluded.