Effect of 2-Chloroethylphosphonic Acid and Cycloheximide on Abscission and Ripening of ‘Bartlett’ Pears1

Abstract

Abstract Branch units of 20 ‘Bartlett’ pear trees were sprayed with 2-chloroethylphosphonic acid (Ethrel) at 250, 500, or 1000 ppm or with cycloheximide (beta-[2-(3,5-dimethyl-2-oxocyclohexyl)-2-hydroxyethyl] glutarimide) at 3, 5, or 20 ppm a wk before the beginning of normal harvest to weaken the abscission layer to facilitate mechanical harvest. Half the trees had been sprayed with naphthaleneacetic acid (NAA) to prevent preharvest drop. Nine days after application, Ethrel at 1000 ppm had significantly reduced the fruit removal force (FRF) on trees that had received no NAA. In contrast, the presence of NAA evidently nullified the abscission-promoting effect of Ethrel. All other treatments failed to reduce FRF significantly. None of the sprays caused discernible phytotoxic effects or hastened fruit maturity. However, after storage for 50 days at 0°C, 17% to 50% of the fruits that received Ethrel at 500 or 1000 ppm, broke down during ripening. Cycloheximide caused no breakdown, but 20% to 80% of the fruits aprayed with 5 or 20 ppm had necrotic spots at the calyx end.