Reducing Floral Initiation and Return Bloom in Pome Fruit Trees--Applications and Implications

Regulation of biennial bearing in pome fruit is usually accomplished by chemically removing fruit during the “on” cycle. The advantages and disadvantages of regulating biennial bearing by inhibiting flowering in the “off” cycle were discussed. Gibberellins and the two phenyl urea cytokinin-like compounds, thidiazuron and CPPU have been shown to inhibit flowering in pome fruit. It was concluded that inhibition of flowering with commercially available gibberellins was not a commercially acceptable approach to regulate biennial bearing. The inhibition of flowering was erratic, fruit thinning and increased fruit set could not be predicted, and seed abortion following gibberellin application could predispose fruit to reduced postharvest life because of reduced calcium uptake. Regulation of flowering by inhibiting flower bud formation appeared to be a viable way to regulate cropping on nonbearing tress or trees that were not carrying a crop.