Chemical thinning "Gala' apple in the midwest

'Gala' trees were treated with various chemical thinners in eight trials co nducted over four years. NAA (naphthalene acetic acid) at 10 ppm applied at 10-12 mm fruit diameter caused reduction in fruit set, hut was not consist ent in causing a fruit size increase. Carbaryl (1-naphthyl N-methylcarbamat e) at 2.5 ml/L applied at 10-12 mm fruit diameter consistently reduced frui t set, increased fruit size and improved return bloom compared to the untre ated controls. At petal fall, application of carbaryl failed to thin 'Gala. ' Accel (1.8% N-(phenylmethyl)-1H-purine-6 amino and 0.18% gibberellic acid ) at 50 ppm did not thin 'Gala' in three of these trials. Endothal (heptani -2,3-dicarboxylate), an experimental bloom th inner, reduced fruit set with an increasing effect with increasing rates. Of the materials currently ava ilable carbaryl, applied at 10-12 mm fruit diameter was the most consistent thinning chemical for 'Gala'.