Fall Ethephon Delays Bloom in ‘Redhaven’ Peach by Delaying Flower Differentiation and Development during Dormancy

Abstract

Ethephon at 120 mg·liter −1 applied to hand-defoliated or nondefoliated trees in late Oct. 1984 delayed ‘Redhaven’ [ Prunus persica (L.) Batsch.] full bloom by ≈5 days in 1985. The same treatment applied on 1 Nov. 1985 delayed full bloom by 9 days in 1986. Hand-defoliation alone was ineffective in delaying bloom in either season. Ethephon treatments increased abscisic acid (ABA) and ethylene levels in dormant buds collected throughout the 1985–86 dormant season. Starch and reducing sugar contents and total chilling requirement were not affected by the ethephon and hand-defoliation. Flower primordia were delayed in differentiation and growth during late fall following a 1986 spray of ethephon. A delay in flower development and growth may be caused by increased levels of ethylene and ABA. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); aminoethoxyvinylglycine (AVG).