Metamitron Replacing Carbaryl in Post Bloom Thinning of Apple Trees

Abstract

ABSTRACT-Carbaryl or the mixture of carbaryl with NAA (naphthalene acetic acid) or BA (benzyladenine) are the post-bloom chemical thinners most widely used in apple thinning in Brazil. The marketing restriction of carbaryl demands new options of apple post-bloom thinners, requiring the evaluation of others compounds for this purpose. Metamitron is one of the substances that may be used in chemical thinning of apples. Metamitron was evaluated at two concentrations, alone or in mixture with BA, in 'MaxiGala', 'Fuji Suprema' and 'Fred Hough' apple cultivars. Applications of metamitron at 384 mg L -1 and at 768 mg L -1 in a mixture with BA, ranging from 40 mg L -1 to 80 mg L -1 , sprayed on fruits with diameter ranging from 5 to 25 mm were compared with the standard treatment and hand thinning. The experimental design was a randomized complete block with 4-6 repetitions of a single plant. The variables analyzed were: fruit set (%); percentage of floral clusters with 1, 2, 3, 4 or more fruits; fruit yield (kg); average fruit fresh mass (g) and percentage of dropped fruit after thinning. Metamitron alone or in combination with BA reduced production per plant and significantly increased the fresh weight of fruits in all cultivars tested. Metamitron at 800 mg L -1 resulted in excessive fruit thinning, especially in 'MaxiGala' cultivar. Metamitron or metamitron + BA have potential to compose the program of chemical thinning of apple trees to replace carbaryl. Index terms: Plant growth regulators, concentration, fruit set, fruit production. METAMITRON COMO SUBSTITUTO DO CARBARYLNO RALEIO PÓS FLORAÇÃO DA MACIEIRA RESUMO-O carbaryl ou a mistura de carbaryl com ANA (ácido naftaleno acético) ou BA (Benziladenina) são os produtos mais utilizados no raleio químico da macieira no Brasil. Com o cancelamento do registro do carbaryl como raleante de pós-floração, são necessárias novas alternativas, sendo importante testar diferentes raleantes com esta finalidade. Dentre as substâncias passíveis de utilização no raleio da macieira insere-se o metamitron. O objetivo deste estudo foi avaliar a resposta da aplicação de metamitron no raleio das macieiras 'Fuji Suprema', 'MaxiGala' e 'Fred Hough'. O uso de metamitron foi testado em duas concentrações, só ou em mistura de tanque com BA, e comparado com BA e BA + etefom, em três cultivares de macieira: 'Maxigala', 'Fuji Suprema' e 'Fred Hough'. Aplicações de 384 mg L -1 e 768 mg L -1 de metamitron em mistura com BA de 40 mg L -1 e 80 mg L -1 aplicado em frutos de 5 a 25 mm de diâmetro foram comparadas com 'tratamento-padrão' e raleio manual. Foi usado o delineamento experimental em blocos ao acaso com cinco a seis repetições. As variáveis analisadas foram: frutificação efetiva (%), percentagem de cachos florais com 1; 2; 3; 4 ou mais frutos por inflorescência, produção por planta (kg), número de frutos por planta, massa média dos frutos (g) e percentagem de queda de frutos após o raleio. O metamitron só, ou em combinação com BA, reduziu a produção por planta e aumentou a massa média dos fr...

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

“…They stated that metamitron application to fruits at early stages increases fruit abscission, since lignin has not formed at these stages yet. The fact that metamitron contributed to higher fruit abscission at early stages was also observed in apples (Petri et al, 2016;Gabardo et al, 2017b).…”

“…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).…”

“…Efficiency in the use of metamitron as a chemical thinner has been associated with certain factors, such as the cultivar, concentration and period of application and weather conditions (McArtney & Obermiller, 2014;Brunner, 2014;Petri et al, 2016). In the south of Brazil, where most peach-growing regions are located, there is little information on both the chemical thinning of peach tree fruits and on the use of metamitron.…”

“…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.…”