THINNING OF 'FUJI' APPLE TREES WITH ETHEPHON, NAD AND BA, ALONE AND IN COMBINATION

The aim of this study was to evaluate the effectiveness of several thinning agents in reducing fruit set in ‘Fuji ’ apple trees. The agents tested were NAD, ethephon, and BA. BA was sprayed at two different times during the thinning period. Multiple sprayings with various combinations of these agents were also evaluated. Ethephon applied alone was the only treatment which significantly increased fruit count at harvest time. None of the treatments had a significant affect on yield, mean fruit weight, the number of first class fruits, or the number of pygmy fruits. Ethephon applied alone was the only treatment which significantly increased the number of second class fruits. All BA alone applications slightly reduced final fruit number and increased mean fruit weight, both not significant. Also BA applied alone significantly reduced the number of second class fruits, regardless of which formulation was used or when it was applied. Key words: apple thinning, ethephon (2-chloroethylphosphonic acid), naphthalene-acetamid (NAD), benzyladenine (BA = N-phenylmethyl-H-purine-6-amine)