Peach Flower Thinning and Possible Sites of Action of Desiccating Chemicals

Abstract

Abstract Airblast application of fertilizers, desiccating herbicides, or surfactants reduced fruit set and increased fruit size of ‘Redhaven’ peach [Prunus persica (L.) Batch]. The addition of the surfactant, aikylaryl polyoxyethylene glyco phosphate ester (Spray Aide), to ammonium thiosulfate (ATS) at rates from 0 ml/liter to 5 ml/liter did not increase thinning. When rates of ATS/ha remained constant, water volumes from 2338 Iiter/ha to 420 liter/ha did not affect thinning. Forty-six percent to 62% more flower buds developed on twigs from chemically thinned trees than on hand thinned trees. Most of this flower bud increase was on the 5 basipetal nodes of current season shoots. Treatment of the stigma, petals + anthers, peduncle, or calyx with ATS reduced fruit-set. Necrotic regions in the peduncle of some flowers could be seen under a microscope 48 hr after treatment. Flowers sprayed with DuPont WK or NH4NO3 + X-77, plus methylene blue (added as a tracer) had blue dye in the veins of the calyx, pedicle, and peduncle of some flowers after 24 hr.