CONTROLLING GROWTH OF BEARING APPLE-TREES WITH ETHEPHON

Ethephon applied 12 to 26 days after full bloom at 1000 to 1500 mg-liter-1 not only substantially inhibited apple (Malus domestica Borkh., spur 'Delicious' strains) tree growth but also caused fruit abscission. Gibberellin plus ethephon did not prevent fruit abscission when ethephon was used at these rates. Several low weekly doses of ethephon controlled tree growth without causing fruit abscission. Ethephon increased fruit soluble solids concentration and substantially reduced fruit starch in the application year. Ethephon greatly increased flowering and fruit set the following season. Fruit length : diameter ratio was not altered by the previous seasons' low weekly doses of ethephon. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).