USE OF METAMITRON AS AN APPLE THINNER/METAMITRON NO RALEIO QUIMICO DA MACIEIRA

The aim of this study was to evaluate the efficacy of metamitron or metamitron plus benzyladenine as a post-bloom thinner on 'Baronesa' and 'Fuji' apples. Three experiments (rate, timing and BA combination) were conducted during two crop seasons, 2013/14 and 2014/15 at the experimental station located in Cacador, SC. Fruit set, fruit drop, yield per tree, fruit size and flowering return were assessed. The efficacy of metamitron was affected by time of application, and when applied at petal fall, promoted the proper adjustment of the production load of plants. Yield per plant reduces, whereas the allocation of fruits in categories of greater size increases proportionally to the increase in the metamitron concentration applied. However, there is excessive fruit drop with the use of high concentrations. The addition of BA to metamitron also promoted fruit drop; however, no difference was observed between single application of metamitron and BA addition. Metamitron shows great potential to be used as thinner for apples, since it reduces the number of fruits per tree. Index terms: Malus domestica, post-bloom thinning, fruit drop, return bloom, fruit quality. O objetivo deste estudo foi avaliar o efeito de diferentes epocas e concentracoes de metamitron e a mistura com benziladenina, no raleio quimico em pos-floracao das macieiras 'Baronesa' e 'Fuji'. Foram conduzidos tres experimentos durante as safras agricolas de 2013/2014 e 2014/2015, no municipio de Cacador-SC. Foram avaliados: a frutificacao efetiva, a queda de frutos, a producao por planta, a distribuicao dos frutos em classes de calibre e o retorno de floracao. A epoca de aplicacao de metamitron influenciou a eficiencia do produto, sendo que, quando aplicado na queda de petalas, este promoveu o adequado ajuste da carga produtiva das plantas. A producao por planta reduz, enquanto a alocacao dos frutos em categorias de maior calibre aumenta, proporcionalmente ao aumento da concentracao de metamitron aplicada. No entanto, ha queda excessiva de frutos com a utilizacao de concentracoes elevadas. A mistura de metamitron com benziladenina, promove a queda de frutos, porem nao ha efeito aditivo entre a mistura e a aplicacao individual de metamitron. O principio ativo metamitron tem potencial para uso num programa de raleio quimico em macieira, visto que reduz a frutificacao. Termos para indexacao: Malus domestica, raleio em pos-floracao, queda de frutos, retorno de floracao, qualidade de frutos.