The cumulative effects of hormone mixtures containing GA3, DPU plus NOXA, NAA or 2,4,5-TP on the cropping and flowering of sweet cherry cultivars,Prunus aviumL.

SummaryMixtures containing 200 ppm GA3, 300 ppm DPU plus 50 ppm NOXA, 10 ppm NAA or 10 ppm 2,4,5-TP were applied each spring to five sweet cherry cultivars in a long-term experiment to investigate cumulative effects on cropping and flowering. Fruit numbers on cvs Napoleon Bigarreau, Early Rivers and Merton Glory branches sprayed with these mixtures were larger than on the control branches in each year of the experiment, despite reduced floral bud numbers in some years. However, the treatments did not always increase cropping on cv Géante d’Hedelfingen, and with Merton Bigarreau no significant improvements in the total crop were obtained for the five-year period of the experiment using the NAA and NOXA mixtures.The effects of the treatments on flowering were separated into those which could be explained by effects on shoot growth and those which appeared to be caused by the treatments per se. In contrast to other years when flowering was mainly suppressed, the treatments per se appeared to increase flowering in 1978 on some ages of wood on some of the cultivars.