The main focus of this work lied on testing the influence of different thinning methods under East Styrian conditions on the yield (harvest, fruit number, fruit size) and the fruit quality of Pinova apple trees in 2010. Single and combined treatments of a tractor attached rope-device for mechanical flower thinning ('Darwin 250'), two approved bioregulators (Ethephon and 6-Benzyladenin) as well as the etching agent Ammonium thiosulfate (foliar fertilizer) were compared to untreated and classical hand-thinned trees. The result illustrated an insufficient effect of the single treatments with the chemical thinners. In contrast to this, all mechanical thinned variants showed a better size grading, without a negative influence on the fruit quality. However, the combination of the machine and Ammonium thiosulfate created an uneconomical, too strong reduction of the yield. In a second step it has been investigated, whether the strength of the annual June-Drop can be predicted by measuring the fruit growth. Based on the data of five variants a US-prediction model and an own, modified model were tested. The modifications of the American-Model ended up in a more precise and practical prediction of the intensity of the June-Drop in this year.