Impact of Thinning Methods on Yield, Diseases and Fruit Quality of Sweet Cherries (Prunus avium L.) in Organic Growing

In 2010, various thinning methods were tested in an organically managed cherry orchard at the experimental farm of the Institute in Vienna. We tested a portable thinning machine (Effleureuse) and a manual method to remove flowers, and thinning of young cherries at the stage of pea size. Between beginning of flowering and full flowering we treated twice with wettable sulphur (4 %), lime sulphur (3 %), vinasse (6 %), potassium soap (Neudosan 6 %) and copper (Cuprofor 0.5 %) as well as ATS (1.8 %) as IP-standard. Additionally to the thinning effect, the impact on fruit size, fruit quality and diseases (Monilinia ssp.) was assessed. Some treatments (Effleureuse, manual thinning of young fruits, lime sulphur, ATS) showed a strong thinning effect and an increase of fruit size. Nevertheless, yield losses due to lower number of fruits caused by thinning could only partly be replaced through higher fruit size. The Effleureuse showed a high thinning effect, because of lower costs it is more suitable for farmers than hand thinning of flowers or fruits. The treatments with lime sulphur and wettable sulphur had a reducing effect on flower infestations with Monilinia laxa. No influence on fruit diseases and internal fruit quality could be found between treatments and control.