Effect of Daminozide, Chlormequat, and Paclobutrazol on Growth and Fruiting of ‘Clapp's Favorite’ Pears

Young ‘Clapp's Favorite’ pear trees (Pyrus communis L.) received soil-applied paclobutrazol at 6 g (a.i.) per tree in Nov. 1983, or foliar sprays of daminozide at 2000 ppm or two sprays of chlormequat at 1600 ppm in June, 1984. Terminal growth was reduced by daminozide and chloromequat the year of treatment and suppressed by chlormequat and increased by paclobutrazol the following year. The number of flower clusters per limb was increased by daminozide and chlormequat. All growth regulators reduced average leaf area and fruit stem length. Fruit length was reduced by paclobutrazol and average fruit weight by daminozide and paclobutrazol. The growth regulators did not affect flesh firmness, soluble solids, or yield. Chemical names used: butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide), 2-chloro-N, N, N-trime-thylethanaminium chloride (chlormequat), β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).