Use of Metamitron as an Apple Thinner

Abstract

-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 Caçador, 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. METAMITRON NO RALEIO QUÍMICO DA MACIEIRARESUMO -O objetivo deste estudo foi avaliar o efeito de diferentes épocas e concentrações de metamitron e a mistura com benziladenina, no raleio químico em pós-floração das macieiras 'Baronesa' e 'Fuji'. Foram conduzidos três experimentos durante as safras agrícolas de 2013/2014 e 2014/2015, no município de Caçador-SC. Foram avaliados: a frutificação efetiva, a queda de frutos, a produção por planta, a distribuição dos frutos em classes de calibre e o retorno de floração. A época de aplicação de metamitron influenciou a eficiência do produto, sendo que, quando aplicado na queda de pétalas, este promoveu o adequado ajuste da carga produtiva das plantas. A produção por planta reduz, enquanto a alocação dos frutos em categorias de maior calibre aumenta, proporcionalmente ao aumento da concentração de metamitron aplicada. No entanto, há queda excessiva de frutos com a utilização de concentrações elevadas. A mistura de metamitron com benziladenina, promove a queda de frutos, porém não há efeito aditivo entre a mistura e a aplicação individual de metamitron. O princípio ativo metamitron tem potencial para uso num programa de raleio químico em macieira, visto que reduz a frutificação. Termos para indexação: Malus domestica, raleio em pós-floração, queda de frutos, retorno de floração, qualidade de frutos. 1 (Paper 002-16).

Comparison of metamitron efficiency for postbloom thinning of young ‘Gala’ and ‘Golden Delicious’ apple trees

“…These combined treatments, unlike single metamitron treatment applied at higher fruit diameter (12-15 mm), successfully overcame the negative influence of low temperature and thinned fruit more aggressively than metamitron applied alone in the first experimental year in both cultivars studied. This disagrees with findings reported by Greene (2014) and Gabardo et al (2017), who demonstrated that metamitron at high concentration combined with the low rate of BA had an additional thinning effect but not greater than that of single metamitron application. These combinations increased the level of thinning to the point of overthinning only in 'Gala' trees and even flowering was abundant, when the temperature during the application and 3 days after was too high.…”

“…In 2016, single metamitron application (concentration of 250 mg L -1 at development stage 12-15 mm fruitlet diameter) in 'Gala' when the temperature was favourable for thinning (minimum night temperature >15 °C, maximum daily temperature >25 °C) significantly reduced crop load to a level that was slightly lower than commercially acceptable. According to previous findings reported by McArtney and Obermiller (2014) and Gabardo et al (2017), excessive fruit drop in some apple cultivars may appear when metamitron is used as an individual thinner at higher concentration. Since the thinning efficacy of the single metamitron application is inconsistent, it seems that unfavourable weather conditions can be overcome by repeated metamitron application or by adding of BA or even NAA in commonly used concentrations.…”

Influence of the Period of Peach Tree Chemical Thinning on Fruit Quality

“…Metamitron may be an efficient alternative to peach tree thinning (McArtney et al, 2012). In apple tree cultures, several thinning processes have already been carried out with metamitron, which has been efficient to make fruits fall (Petri et al, 2016;Goulart et al, 2017;Gabardo et al, 2017).…”

Application time of chemical thinning with metamitron in ‘Sensação’ peach trees

“…Metamitron has shown adequate results in relation to thinning apple tree fruits by inhibiting photosynthesis (Petri et al, 2016;Goulart et al, 2017;Gabardo et al, 2017a). Fruits, throughout their development, are the main drains of end products of photosynthesis; in the case of interruption or decrease in the photosynthetic rate, fruits may fall due to competition (Gabardo et al, 2017a). Metamitron acts on Photosystem II by inhibiting electron transport its effect occurs because it acts on Photosystem II and inhibits electron transport on the chloroplast of plastoquinone QA to QB.…”

“…According to Pavanello & Ayub (2012), the ideal chemical thinner is the one that can lead to partial fruit abscission soon after a single application. Several studies have shown satisfactory results of metamitron as a chemical thinner in apple tree cultures (Petri et al, 2016;Goulart et al, 2017;Gabardo et al, 2017a), even though there is no information on peach tree cultures in Brazil. Therefore, this study aimed at evaluating the thinning effect of metamitron on peach trees at different periods of time after bloom in the south of Brazil.…”