The peach industry is of great economic importance in Southern Brazil. The state of Rio Grande do Sul is the major peach producer in the country. About 50% of the production areas of the state are located in its southern half. The main problem of peach production is the very concentrated harvest season. Fruit size is also a problem. Therefore the objectives of the present work were to increase fruit size and to spread the harvesting period of peaches cv. Diamante by the application of 3,5,6-tricloro-2-piridil-oxiacetic acid (3,5,6-TPA; free acid and amine alcohol) or 2,4-diclorofenoxipropionic acid (2,4-DP; ester) as well as associate these chemicals with and without ringing of branches. The evaluations were performed in the season 1999/2000 on plants at the Experimental Agricultural Station of Federal University of Rio Grande do Sul, located in Eldorado do Sul, latitude 30º39'S, longitude of 51º06'W and altitud of 46 meters. The following treatments were applied in a randomized block design with 4 replications and one plant as experimental unit: 1) 10 mg.L-1 of 3,5,6-TPA amine alcohol 2) 20 mg.L-1 of 3,5,6-TPA amine alcohol 3) 30 mg.L-1 of 3,5,6-TPA amine alcohol 4) 20 mg.L-1 of 3,5,6-TPA, amine alcohol plus ringing of branches; 5) 30 mg.L-1 of 3,5,6-TPA free acid; 6) 30 mg.L-1 of 3,5,6-TPA free acid plus ringing of branches; 7) 25 mg.L-1 of 2,4-DP; 8) 50 mg.L-1 of 2,4-DP; 9) 75 mg.L-1 of 2,4-DP; 10) 50 mg.L-1 of 2,4-DP plus ringing of branches; 11) ringing of branches in September and 12) control, with no treatment at all. Auxin application does not increase total fruit production of peach trees. However, auxin treatments, specially 3,5,6-TPA free acid, anticipated peach harvest for about 20 days in comparison to control trees. The treatments with 30 mg.L-1 of 3,5,6-TPA free acid result in increments of diameter and length in comparison to, but are not significantly diffent from all other treatments. The treatments 20 mg.L-1 of 3,5,6-TPA amine alcohol and 75 mg.L-1 of 2,4-DP (éster) anticipated peach harvest for about 20 days, which was not statistics different from the the 30 mg.L-1 of 3,5,6-TPA free acid treatments. Classification of peachs in first class fruit was highest in the 30 mg.L-1 of 3,5,6-TPA free acid + (ringing) and 20 mg.L-1 of 3,5,6-TPA, amine alcohol, but not differing statistics with the control.
Prunus persica; crop precocity; fruit quality; girdling; growth regulator
