Crop-load management is a vital cultural measure in apple-growing. Only when the number of fruits per tree corresponds to target crop-load levels do yield and quality match over the years. Crop load is influenced by various factors, and is deliberately reduced through thinning measures. The necessary intensity of thinning, however, is difficult to gauge, since the process must take place before the physiological fruit drop is over in early summer. Three approaches to early forecasting of crop load were refined, adapted and evaluated on fruit plots in Switzerland, Germany, Austria and Italy: fruit-growth measurement according to D.W. Greene; determination of the material composition of the fruit by means of near-infrared spectroscopy; and carbon-balance modelling (MaluSim). According to the investigations, fruit drop is not induced at a specific time, but can be induced repeatedly. Because of this, with the current state of developments, the quality and reliability of the forecasts were insufficient for application in practice. Nevertheless, the estimation of the expected effectiveness of a thinning treatment which can be derived using the carbon balance from MaluSim is promising, and would allow the dosage for the treatment to be specially adapted to the conditions in question.
Zufferey V., Delabays N., Verdenal T., Reynard J.- S., Dienes A., Belcher S., Lorenzini F., Bieri S., Blackford M., Bourdin G., Spangenberg J.-E., Carlen C., Spring J.-L.
Reynard J.- S., Spring J.-L., Verdenal T., Zufferey V., Bourdin G., Bieri S., Carlen C., Crettenand F., Favre G.