Bloom Thinning of `Winblo' Peach and `Fantasia' Nectarine with Monocarbamide Dihydrogensulfate

Abstract

Mature `Winblo'/Lovell peach [Prunus persica (L.) Batsch] trees in Georgia were treated with five concentrations of D-88, a 79 % to 82 % active ingredient formulation of monocarbamide dihydrogensulfate: 0 (water only), 2.5, 5.0, 7.5, and 10.0 ml·liter-1. All treatments were made by airblast application at 1200 liters·ha-1 when trees were at 95% full bloom. The number of flowers on three limbs per tree was counted 3 days before and fruitlets 25 days following treatment. Regression analysis revealed a linear thinning response to concentration, with 10.0 m1·liter-1 reducing the number of flowers per limb cross-sectional area by 56% over the nonthinned control. Mature `Fantasia' nectarine trees in New Zealand were treated with four concentrations of D-88: 0 (water only), 2.5, 3.75, and 5.0 ml·liter-1. All treatments were made by handgun application to runoff when trees were ≈2 days past full bloom. The number of flowers per limb was counted 6 days before and fruit 62 days following treatment. Regression analysis revealed a linear thinning response to concentration, with 5.0 ml·liter-1 reducing the number of flowers per limb by 55 % over the nonthinned control. Total yield (kilograms of fruit) per tree was the same for all treatments, although fruit size on sprayed trees was larger. No phytotoxicity or fruit finish injury was observed.