USE OF NEW BLOSSOM THINNERS TO REDUCE FRUIT SET AND IMPROVE FRUIT QUALITY IN APPLES, PEACHES, NECTARINES, AND PLUMS

Effects of ammonium thiosulfate (ATS) on fruit set, fruit quality, and yield of ‘Fuji’ apple (Malus domestica Bork.) were studied in 2000. Double applications of ATS at a rate of 15 ml·L^-1 or a single application of this chemical at a rate of 25 ml· L^-1 resulted in satisfactory levels of thinning in ‘Fuji’ apple. Double applications of ATS at a rate of 25 ml·L^-1 resulted in excessive thinning. Also, effects of Tergitol-TMN-6 on fruit set, quality, and yield in ‘August Lady’ and ‘Zee Lady’ peaches [(Prunus persica (L.) Batsch] in 2004 and 2006, in ‘July Red’ nectarine in 2005, and in ‘Empress’ plum [(Prunus domestica (L.)] in 2004 were studied. In addition to Tergitol-TMN-6, the effect of Crocker’s Fish Oil (CFO) in combination with lime sulfur on fruit set, quality, and yield in ‘July Red’ nectarine in 2005 was studied. Tergitol-TMN-6 at 5 ml·L^-1 or higher rates and applied at about 75-80% bloom reduced fruit set without russeting peach fruit. Peach fruit size was often increased by Tergitol-TMN-6 treatment. Tergitol-TMN-6 at 7.5 or 10 ml·L^-1 and applied either once at 75-80% bloom or twice at 35% bloom and again at 75-80% bloom, reduced fruit set without any fruit russeting in nectarine. Tergitol-TMN-6 at 7.5 to 12.5 ml· L^-1 reduced fruit set and increased fruit size in ‘Empress’ plum.