ISHS Acta Horticulturae 80: Symposium on Growth Regulators in Fruit Production
ALTERATION OF YOUNG APPLE TREE STRUCTURE WITH 2,3-DIHYDRO-5,6- DIPHENYL-1,4-OXATHIIN (UBI-P-293) |
| Authors: | Don C. Elfving, C.G. Forshey |
| Abstract:
UBI-P-293 was applied alone or in combination with daminozide and/or ethephon to young apple trees shortly after bloom. The P-293 treatments caused slowing or cessation of activity of terminal growing points and stimulated much lateral bud-break. Total growth from branches of treated trees was increased; this increase was the result of more branches of smaller average lengths. Increased branching from older wood was also observed. Where daminozide and ethephon were combined with P-293, buds activated by P-293 made little growth and formed spurs. Cultivar and timing of the treatments in relation to growth had marked effects on results. P-293 effectively thinned fruit at concentrations below the level necessary to influence vegetative growth. At levels which induced branching, virtually all fruit were eliminated. Effects of P-293 on flowering were dependent on cultivar and additional treatments. P-293 alone had little or no influence on the flowers on "Delicious" but inhibited flower development in "McIntosh". Ethephon or daminozide plus ethephon overcame the inhibitory effect of P-193 and increased flowering over controls in the early applications but failed to do so in later trials. Possible uses of this approach in canopy development of young trees will be discussed. | |
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