Effects of Hydrogen Cyanamide, Ammonium Thiosulfate, Endothalic Acid, and Sulfcarbamide on Blossom Thinning, Fruit Quality, and Yield of Apples

Abstract

Effects of rates and/or timings of hydrogen cyanamide (Dormex™), ammonium thiosulfate (ATS), endothalic acid (Endothal), and/or sulfcarbamide (Wilthin®) on blossom thinning (fruit set), fruit quality, and yield of ‘Delicious’, ‘Law Rome Beauty ’, ‘Fuji’ and ‘Jonathan’ apples ( Malus x domesticaBorkh.) were studied. In ‘Delicious’, application of Dormex™ at 1.56 or 2.34 mL.L ^-1(v/v) or ATS at 16 or 24 mL.L ^-1(v/v) reduced fruit set and increased fruit size. In ‘Delicious’, reduction of fruit set with application of Dormex™ at 1.56 mL.L ^-1(v/v) resulted in a significant increase in yield. In ‘Law Rome Beauty’, application of Dormex™ at 3.12 mL.L ^-1(v/v) or ATS at 16 or 24 mL.L ^-1(v/v) reduced fruit set in two years. Also, application of Endothal once at 1.88 mL.L ^-1or twice at 1.25 mL.L ^-1(v/v) reduced fruit set in ‘Law Rome Beauty’. One application of ATS at 25 or 30 mL.L ^-1(v/v) or two applications of ATS at 15 or 25 mL.L ^-1(v/v) reduced fruit set of ‘Fuji’. In ‘Jonathan’, one or two applications of ATS at 25 mL.L ^-1(v/v) reduced fruit set.