Interaction between varierties, lime sulphur and hainet on the thinning effect and on side effects using paraffin oil as a June drop thinner

摘要

In organic apple growing in South Tyrol, (Italy) 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 leaves is drastically reduced. Notwithstanding the good trial results, the method is not used in the field, because shading trees with nets is labour-intensive and expensive. During the last years 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 russetting, cannot be excluded. In this experiment, the paraffin oil-based products UFO (Ultra Fine Oil) and EKO (EKO Oil spray) were applied on different apple cultivars and their thinning efficacy and interaction with lime sulphur sprays and hail nets were recorded. There have been promising results in thinning, but differences in the observed effects among apple cultivars were high. Therefore, the choice of product and thinning strategy strongly depends onthe cultivar.