Response of Bosc and Cold Snap™ pears to thinning with NAA, 6-BA, ACC, and s-ABA

Adjusting the crop-load of European pears [Pyrus communis L.] by hand thinning is currently required to ensure marketable size of most cultivars grown in Ontario. The benefits of chemical thinning pears and their effect on fruit quality and fresh-market returns was investigated in a three-year study where a series of foliar chemical thinning sprays was applied during the 10-mm fruitlet stage to Bosc and Cold Snap™ pear trees growing in commercial orchards in the Niagara Peninsula, Ontario. Treatments included an untreated and hand-thinned control, and two concentrations each of 6-benzyladenine (6-BA; 75 mg L-1 and 150 mg L-1), naphthalene acetic acid (10 mg L-1 and 20 mg L-1), 1-aminocyclopropane carboxylic acid (150 mg L-1 and 300 mg L-1) and s-abscisic acid (s-ABA; 150 mg L-1 and 300 mg L-1). Overall, all thinning products reduced crop load at least once in the three-year study, although this varied by year and cultivar. Higher concentrations were more effective than lower concentrations. Napthalene ace...