The thinning of fruit until the physiologically optimal number of fruit is reached is essential in fruit cultivation to achieve regular yields of a good, storable quality. In organic farming, growth regulators are not permitted; thus, this project aims to find suitable alternative methods that adhere to organic farming regulations.
We test different different natural products (mostly dissecants) and physical methods (e.g. rope thinner, or shadow nets) for their thinning efficacy – alone or in various combi-nations, or application dates. Usually we apply the test methods on 4-6 cultivars with at least 2-4 replicated plots of 18 trees per cultivar. We apply the products with a commer-cial axial sprayer to achieve practical circumstances. We count a) flower set before treatment, b) fruit set after treatments before June drop, c) fruit set after June drop; d) fruit set before harvest, e) negative side-effects such as russeting or phytotoxicity; f) return to bloom in the following spring. Before practical recommendations are made, the method is tested for about 3 years.