Effects of Fall Ethephon and Gibberellic Acid Applications on Bloom Delay, Flowering, and Fruiting of Plum

Abstract

<jats:p>The influence of fall applications of ethephon and gibberellic acid to produce bloom delay in `Wade' plum were carried out in 1987-89. Single saturation applications of ethephon at either 125 and 250 mg·liter<jats:sup>-1</jats:sup> with 50 mg·liter<jats:sup>-1</jats:sup> gibberellic acid (GA<jats:sub>3</jats:sub>) at first sign of leaf fall in October of 1987 produced bloom delay of 6-17 days the following spring. No difference in bloom delay was seen between the two treatments. Gummosis and death of some lateral shoots were observed in both treatments but was more severe at the higher ethephon concentration. There was no adverse effect on flower bud opening in either treatment, In 1988 untreated trees suffered 100% fruit loss because of frost injury while both treatments allowed for excellent yields as a result of frost avoidance. In the fall-spring of 1988-89 the experiment was repeated on the same trees; a 5-8 day delay in bloom was observed in both treatments but a late freeze destroyed all fruit on both treated and untreated trees.</jats:p>