Effect of defoliation on vegetative bud break, spring bloom, and bud abscisic acid levels of peach, Prunus persica (L.) batsch

Abstract

Individual June defoliated 'Redskin' peach shoots failed to force lateral leaf and flower buds until the following spring. When major portions of mature trees were defoliated the percent of resulting leaf bud break was proportional to the severity of defoliation. Flower buds forced in response to defoliation treatments were occasionally atypical and never broke in substantial numbers until the following spring. A positive association appeared to exist between fall defoliation date, spring bloom date, and December bud abscisic acid (ABA) levels. Trees defoliated early demonstrated earlier bloom the following spring and lower December bud ABA levels than trees allowed to lose their leaves naturally. The maintenance of foliage late into the fall had beneficial effects on bloom retardation, tree growth, and yield. A positive correlation was found between chilling requirement and December bud ABA levels of three cultivars tested. Abscisic acid concentrations in young peach levels increased from early summer to September and then decreased to leaf fall. Abscisic acid levels in mature peach leaves followed the same trend except in early summer.