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

Abstract

Thinning is a cultural practice that leads to balance between fruit yield and quality. It is carried out in a short period of time and requires qualified workforce, whose shortage ends up increasing costs. This study aimed at evaluating the thinning effect of metamitron on peach trees at different periods of time after bloom. The experiment was carried out in a commercial orchard of 'Sensação' peach trees located in Morro Redondo, Rio Grande do Sul (RS) state, Brazil, in 2015-2016 crops. Treatments were the application of 200 mg L-1 metamitron, 20, 30, 40, 50 and 60 days after full bloom (DAFB), and manual thinning 40 DAFB. Fruit abscission, effective fructification, period of manual and chemical thinning, number of fruits and yield per plant, mean fruit mass and fruit caliber were evaluated. When metamitron was applied 40 DAFB, percentages of fruit abscission and fruit set, besides the number of fruits, were similar to the ones found when manual thinning was carried out. The intensity of the thinning effect of metamitron in peach trees depends on the application period.

Metamitron in the chemical thinning of ‘PS 10711’ peach trees

“…According to McArtney and Obermiller (2014), metamitron changes the photosynthetic apparatus for 7 to 10 days after its application, reducing electron transport rates by up to 60%. Farias et al (2020) reported that the intensity and oscillation of solar radiation influences the rate of abscission in peach fruits. Thus, as seen in the apple tree (Petri, Hawerroth, Berenhauser, & Couto, 2013), the results obtained with the use of chemical thinner in the peach tree depend on the interaction between genotype and climatic conditions.…”

“…In view of the need to ensure the efficiency of thinning as well as reduce labor, new studies propose chemical thinning as an alternative to the hand thinning of fruits (Petri et al, 2016;Barreto et al, 2018b;Farias et al, 2019a;Farias, Barreto, Zandoná, Martins, & Mello-Farias, 2020). Chemical thinning consists of the application of chemicals during or shortly after bloom, which causes the abscission of flowers and/or fruits, thereby reducing or eliminating the need for hand thinning (Pavanello & Ayub, 2012).…”

“…Some studies have shown the potential of chemical thinning in the peach crop (Taheri, Cline, Jayasankar, & Pauls, 2012;Giovanaz et al, 2016;Barreto et al, 2018a;Farias et al, 2020). In temperate fruit trees, chemical thinning has been performed with products with hormonal action or products which act on the electron transport chain between photosystems, such as metamitron (Petri et al, 2016;Goulart et al, 2017;Gabardo et al, 2017a;Farias et al, 2019aFarias et al, , 2020. This product has been used mainly for thinning apple trees in southern Brazil and has shown satisfactory results in reducing fruit load (Petri et al, 2016;Gabardo et al, 2017a).…”

“…Metamitron acts on photosystem II by inhibiting electron transport from the chloroplast of plastoquinone QA to QB, reducing CO 2 fixation and the production of ATP and NADPH and consequently inhibiting photosynthesis (Basak, 2011;Stern, 2014). When applied to fruits, metamitron contributes to their physiological drop (Gabardo et al, 2017a), since photosynthetic inefficiency reduces the production of carbohydrates necessary for fruit fixation (Farias et al, 2019b(Farias et al, , 2020). However, the success of chemical thinning depends on genetic traits of the cultivar, the concentration used and the appropriate phenological stage for application (Brunner, 2014;Mcartney & Obermiller, 2014).…”

Carbohydrate content in branches and abscission of fruit of peach trees subjected to chemical thinning

“…Since peach (Prunus spp.) trees exhibit abundant blooming, thinning practices are necessary in orchards to decrease total fruit load and keep energy balance (Farias et al, 2020b). These practices result in larger fruits, with an unique flavor and an adequate color throughout commercialization (Farias et al, 2019).…”