Metamitron in the chemical thinning of 'PS 10711' peach trees

Chemical thinning of fruits may be an alternative practice to hand thinning. Hand thinning must be performed in a short time during the fruiting stage, but lack of manpower and the onerous costs of the operation make it increasingly difficult to employ it at the right time and at the ideal intensity. The objective of this study was to examine the effect of different concentrations of metamitron as a chemical thinner on 'PS 10711' peach trees. The experiment was carried out during two harvests in an orchard in the municipality of Eldorado do Sul, in the Central Depression region of the state of Rio Grande do Sul, Brazil. Treatments consisted of the application of metamitron at the concentrations of 100, 200, 300 and 400 mg L-1; hand thinning; and no thinning. The fruits were thinned chemically and by hand 40 days after the peach trees were in full bloom. Fruit abscission, fruit set, number of fruits, production per tree and fruit quality were evaluated. Metamitron has a thinning effect on the peaches of cultivar PS 10711. The metamitron concentrations of 100 and 200 mg L-1 result in less fruit abscission as compared with hand thinning. The thinning effect of metamitron alters production per tree, but does not interfere with fruit quality.