SPRAYING TECHNIQUES AND THE EFFICIENCY OF THINNING AGENTS I. SPRAY VOLUME AND CONCENTRATION IN RELATION TO CROWN SIZE

The aim of this study was to improve the methods of thinning in order to reduce the contamination of the environment by chemical thinning agents and to increase the repeatability of the effects they produce. It has been suggested that incorrect application of the preparations for fruitlet thinning is one of the main reasons for the lack of repeatability of the effects of thinning. The experimental results related to the method of application of one type of preparation are not necessarily repeatable when using other chemical thinning agents. NAA was the best thinning agent when applied at low concentration and high spray volume, whereas ATS was the best at high concentration and low spray volume. In contrast, the effectiveness of BA increased as both its concentration and the volume of liquid used increased. The volume of the spray solution applied should be determined on the basis of tree crown size and not as volume per ha only. The results of the study show that bioregulators used for thinning fruitlets can also be useful for evaluating the efficacy of spraying techniques.