BLOSSOM THINNING AS A STRATEGY IN CHEMICAL THINNING OF APPLES IN NEW ENGLAND

Experiments were initiated to evaluate the effectiveness of several compounds as blossom thinning chemicals on ‘Starkrimson Delicious’ apples.
In one experiment, sulfcarbamide (monocarbamide dihydrogen sulfate, Wilthin) at 0.25 L/100 L water was compared with endothall (7, oxybicylo (2,2,2) heptane-2-3 dicarboxylic acid) at 0.125 to 0.25 L/110 L and pelargonic acid (Thinex) at 0.25 L/100 L. Sulfcarbamide and pelargonic acid thinned comparably to the standard postbloom thinning treatment of naphthaleneacetic acid (NAA) at 6 mg L^-1 plus carbaryl, at 600 mg L^-1. All blossom thinning treatments increased fruit size at harvest, whereas standard blossom thinning NAA plus carbaryl did not.
Only NAA plus carbaryl caused pygmy fruit formation.
In another experiment on ‘Starkrimson Delicious’, thinning with a single application of endothall applied at 80-100% bloom at either 0.94, 0.125 or 0.188 L/100 L, was compared with double applications at 30-40% and 80-100% bloom at the same concentrations.
Endothall at 1.88 L/100 L thinned more than endothall at 0.94 L/100 L. Regardless of concentration, two applications of endothall thinned more than one.
A single application of endothall at 0.188 L/100 L thinned comparably to the standard postbloom thinning treatment of 6 mg L^-1 NAA plus carbaryl at 600 mg L^-1.

XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees

D.W. Greene

fruit thinning, fruit set, pollination inhibitors, Malus domestica

https://doi.org/10.17660/ActaHortic.2004.636.40