Time of metamitron application and concentration in the chemical thinning of ‘Maciel’ peach

Abstract

In the peach tree cultivation, the producer has the challenge of obtaining good quality fruits and maintaining production in a balanced way over the years. Thinning favors these parameters and reduces the fruit load on plants. Manual thinning commonly practiced on peach trees requires high labor and increases production costs. Chemical thinning as an alternative to manual thinning, which depending on the species, time and concentration, has demonstrated high efficiency. The aim of this study was to evaluate the effect of metamitron applied at different seasons and concentrations on the chemical thinning of peach trees in southern Brazil. Experiments were conducted in a commercial peach orchard (‘Maciel’ cultivar), in the municipality of Morro Redondo, Rio Grande do Sul, Brazil, during the 2015 and 2016 harvests. In experiment 1, metamitron at concentration of 200 mg L-1 was applied at 20, 30, 40, 50 and 60 days after full bloom and manual thinning performed at 40 days after full bloom. In experiment 2, metamitron was applied at concentrations of 100 mg L-1, 200 mg L-1, 300 mg L-1 and 400 mg L-1 and manual thinning at 40 days after full bloom, in addition to control plants. Fruit abscission, fruit set, total number of fruits per plant, yield per plant, average mass and fruit diameter were evaluated. Metamitron at concentration of 200 mg L-1 has thinning effect when applied before 40 days after full bloom. Metamitron concentration of 100 mg L-1 applied at 40 DAFB promoted fruit abscission superior to manual thinning. Therefore, the application of metamitron to ‘Maciel’ peach trees close to full bloom at concentration of 100 mg L-1 results in thinning practice similar to manual thinning.

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

“…Besides, Figure 2 shows that environmental conditions, regarding temperature, were similar in both years (14-19 °C). Even though 'Maciel' peach trees had different behavior from the one in the year of application, they did not exhibit any trend in fruit set in relation to the period in which metamitron was applied (Farias et al, 2019). According to Nava et al (2009), peach trees usually have high fruit set rates, with the contribution of environmental conditions, such as sunny, mild and dry days during blooming.…”

“…In the 2016 crop, the lowest percentages of fruit abscission were found in plants thinned with metamitron 50 DAFB and 60 DAFB. According to Farias et al (2019), the highest percentages of fruit abscission in 'Maciel' peach trees with the use of metamitron occurred 20 and 40 DAFB. They stated that metamitron application to fruits at early stages increases fruit abscission, since lignin has not formed at these stages yet.…”

“…In 2016, thinning treatments did not show any difference regarding yield per plant. Productivity and mean fruit mass of fruits borne by 'Maciel' cultivars were not affected by metamitron, regardless of its application period (Farias et al, 2019). and 2016 (B) crops.…”

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

“…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).…”

Chemical thinning of 'BRS Kampai' peach trees

“…In apple trees, it has shown satisfactory results in fruit thinning by inhibiting photosynthesis (Petri et al, 2016;Gabardo et al, 2017;Goulart et al, 2017). In 'Contender' peach trees, however, the application of 100 to 400 mg L -1 metamitron did not show satisfactory results for chemical thinning (McArtney et al, 2012), whereas 100 mg L -1 metamitron applied to 'Maciel' peach trees close to full bloom acted similarly to manual thinning (Farias et al, 2019).…”