Thinning promotes an increase in fruit size, balance between vegetative growth and productive and prevents switching of production. The aim of this study was to evaluate the effect of different concentrations of ethephon on chemical thinning of plum cv. Irati, at 4 years old on rootstock A-9 spaced 5.0 x 2.5 m, in the municipality of Arapoti - PR. Five treatments were tested at ethephon concentrations of 0.1; 0.125; 0.15; 0.2 mg L-1, applied 30 days after full bloom. The following characteristics were evaluated: average number of fruits per branch, number of fruits form whole plant at harvest point, yield per plant, fruit weight, fruit diameter, soluble solids, fruit stiffness, acidity, pH and color. Increased in the concentration of ethephon linearly reduced the number of fruit, I, II and III diameter, increasing the number of fruit of IV diameter, larger fruit, obtained with the concentration of 0.093 mg L-1 of ethephon. The drought in August and September may have affected the smooth fruit development.
Prunussalicina; 2-chloroethylphosphonic acid; fruit set
