Soybean Oil as a Prebloom Flower Bud Thinner for Peaches

Abstract

Survival of peach flowers during spring or winter freezes and large fruit size at harvest are critical for profitable peach production in the Southeast. Delaying both bud swell in late winter and flower phenology in spring reduces the risk of flower bud death from cold temperatures. Preliminary research in Tennessee using soybean oil (SO) as a dormant oil spray in place of Superior oil showed SO delayed peach bloom, thinned flower buds, and increased fruit size. In 1997, a `Harvester' peach orchard in Monetta, S.C., and a `Redhaven' orchard near Clemson, S.C., were sprayed in early February with 0%, 6%, 8%, 10%, and 12% SO mixed with 1% (by volume) Latron B-1956. Number of dead flower buds and the flower bud stages for each SO treatment were recorded during the first pink to full bloom flowering period. Excess fruit were hand-thinned in late April. Fruit set, maturity date, weight, and yield/tree were taken. Bud death increased from 14% (control) to 17% to 20% at the 8%, 10%, and 12% SO rates for `Redhaven' and from 13% (control) to 21% at the 10% and 12% rates for `Harvester'. Phenology was delayed 3-4 days for `Redhaven' at 8%, 10%, and 12% SO, but no differences were noted in the `Harvester' trees. No differences in fruit maturity occurred. Fruit weight and yield/tree was higher for all `Harvester' SO treatments and the `Redhaven' 10% and 12% SO treatments. No shoot phytotoxicity was observed.