Chemical thinning of Royal gala apples with naftalen acetic acid (naa) and carbaril mixtures

Gabino Reginato M.1, Pablo Valdés de F. y Cristina Castillo T.

During the growing season 1995/96 in Placilla, Sixth region of Chile, mixtures of naphthalene acetic acid (NAA, 0, 6 and 9 mg L-1) with Carbaryl (0, 300 and 600 mg L-1) were sprayed on "Royal Gala" apples, in order to test their effects upon fruit thinning. All treatments were applied at the petal fall stage or 10 days after. They were also applied separately, NAA on pink bud and Carbaryl 20 days after full blossom. Sixty days after blossom and at harvest the fruit load was evaluated in terms of fruits/cm2 of trunk cross sectional area (TCSA). Furthermore, fruit characterístics were evaluated at harvest. Data was analysed through regression and correlation analyses. NAA plus carbaryl thinning effects were proportional to the concentration of both products in all trials, reaching more than desirable effects with the highest rates. Initial fruit loads (final fruit set) close to 5 fruits cm-2 of TCSA after chemical thinning was reached with 6 mg L-1 of NAA combined with 300 to 600 of Carbaryl; a slightly higher effect was observed with earlier applications. Applying NAA plus Carbaryl separately or in mixture produced a similar effect.

Keywords: Chemical thinning, Malus domestica, Royal Gala, growth regulators, apple.
1 Universidad de Chile. Facultad de Ciencias Agronómicas, Casilla 1004, Santiago, Chile. E-mail: greginat@abello.dic.uchile.cl.