EFFECT OF ROOT PRUNING AND SUMMER PRUNING ON GROWTH, YIELD, QUALITY, AND FRUIT MATURITY OF MCINTOSH APPLE TREES

Mature ‘McIntosh’/M.7 apple (Malus domestica Borkh.) trees were treated as follows: 1) control; 2) root pruned at full bloom; 3) summer pruned in mid-August; or 4) root and summer pruned to determine the effect of the treatments on fruit maturity and preharvest fruit drop. The treatments were applied annually in a split-plot design with eight replications. Root pruning reduced preharvest drop, internal ethylene content of the fruit, and starch index rating. Summer pruning increased preharvest drop in 1988 but not in 1989 or 1990. Internal ethylene concentration of fruit was not affected by summer pruning, but fruit from summer-pruned trees had higher starch indices. There were no significant year x treatment, treatment x sample date or root pruning x summer pruning interactions on maturity indices.

Relative ripening date and internal fruit ethylene concentration at harvest were not significant covariates overall or within years for preharvest drop. Nor was starch index rating a significant covariate for preharvest drop.

It was impossible to determine from this study if the mechanism was related to maturity, but root pruning reduced preharvest drop 52%.