MANAGING HIGH VIGOR IN BEARING ORCHARDS: CONTROLLING GROWTH WITH ETHEPHON

Abstract

Ethephon application at rates of 1000 ppm to 1500 ppm substantially inhibited tree growth but also caused fruit abscission. Application of gibberellin plus ethephon did not prevent fruit abscission. Low weekly doses of ethephon did not cause fruit abscission but gave good control of tree growth. Ethephon increased soluble solids and substantially reduced starch in the year of application. Flowering and fruit set were greatly increased by ethephon sprays the previous season. Fruit diameter or length:diameter ratios (L/D ratio) were not altered by the previous seasons' low weekly doses of ethephon.Complete or partial loss of fruit in high density apple plantings can result in excessive shoot growth that is normally controlled by cropping. Spot spraying with ethephon in the top part of `Redchief Delicious'/MM. 26 trees for tree training purposes increased the number of shoots over 10 cm in the lower part of the tree, but also caused fruit abscission in the unsprayed parts of the tree. Summer training of high density plantings of fireblight susceptible varieties with spot sprays of ethephon would reduce the need for cutting or pinching branches during the tree growth period.