Direct and apparent residual effects of prohexadione – calcium applied to young cropping sweet cherry trees

The same young cropping ‘Regina’ sweet cherry trees were foliar treated with prohexadione-calcium (Pro- Ca) in two consecutive years at a concentration of [ 125, 125 x 2, 250 ]-(A) and [ 250, 375, 500 ]-(B) mg ProCa l-1, respectively. The following year some trees from A-treatments were left untreated to observe carry-over effects (C). None of A-treatments influenced tree trunk, shoot extension and internode growth, whereas B-treatments reduced shoot extension and internode length, simultaneously increasing flower bud density, particularly by 500 mg ProCa l-1. There were no carry-over effects produced by C-trees, except some retardation in shoot extension. None of the treatments influenced the tree cropping level. Fruit diameter was reduced by A-treatments, but fruit shape (L/D ratio) and mass were reduced by treatments B, and such reduction was also exhibited by C-trees (residual effects).