EFFECTS OF PROHEXADIONE-CALCIUM AND ETHEPHON ON GROWTH AND FLOWERING OF 'BING' SWEET CHERRY

Single applications of prohexadione-Calcium (P-Ca, Apogee^®, BASF) or ethephon (ETH, Ethrel^®, Aventis CropScience) to young, non-cropping ‘Bing’/Mazzard sweet cherry trees produced short-term reductions in terminal shoot elongation rate but did not reduce total seasonal shoot growth. Application of a tank-mix of P-Ca and ETH produced a stronger reduction in shoot growth rate. Single applications of P-Ca alone were ineffective for promoting flower bud formation; single applications of a P-Ca/ETH tank mix either increased flower bud density on previous season shoot growth or had no effect. Increased flower bud density on both previous season shoots and spurs on older wood was observed only when a tank mix of P-Ca and ETH was applied twice to the same trees three weeks apart. This treatment not only increased flower bud density approximately 3-fold over untreated trees, but yield efficiency also was increased nearly 3-fold.