BLOOM THINNING LOADEL CLING PEACH WITH A SURFACTANT

Hand thinning fruit is required every season to ensure large fruit siz e of 'Loadel' cling peach [Prunus persica (L.) Batsch] in California. Chemical thinning may lower costs of hand thinning. A surfactant, Armo thin N-bis-2-(omega-hydroxypolyoxyene/polyoxypropylene) ethyl alkylami ne]; AKZO-Nobel, Chicago; AR}, was sprayed at 80 % of full bloom (PB), FB, and EB + 3 days. The spray volume was 935 liter/ha. Concentration s of AR were 1%, 3%, and 5% (v/v). An early hand thinning in late Apri l, a normal hand thinning at 13 days before standard reference date (e arly May), and a nonthinned control were compared to bloom-thinned tre es for set, yield, and fruit quality, AR resulted in no damage to frui t; however, slight leaf yellowing and burn and small shoot dieback wer e seen at the 5% concentration. Fruit set, and therefore, the number o f fruit that had to be hand thinned, were reduced with 3% AR applied a t 80% FB and 5% AR applied at all bloom phenophases (stages of bloom d evelopment). Thinning time was reduced by 37% (5% AR applied at 80% FB ), 28% (5% applied at FB), and by 20% (3% applied at 80% of FB), compa red to the normally hand-thinned control. Although AR resulted in earl y size (cross suture diameter and weight) advantages, at harvest there were no significant differences in fruit size among all AR treatments and the normally hand-thinned control. Total and salable yields of AR treatments and the normally hand-thinned control were equal. Armothin shows promise for chemical thinning of peach when used as a bloom thi nner.