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

Abstract

Introduction Establishing new apple orchards using well-feathered apple trees has recently become common practice. In favourable growing conditions, these trees can produce high yield in the second leaf, achieving full productivity in the fourth leaf (Radivojevic et al., 2014). High-quality trees of the cultivars 'Gala' and 'Golden Delicious' during the establishing period frequently produce an excessive number of fruitlets but this can be insufficient to guarantee fruit of good marketable size at harvest (Bregoli et al., 2007). Furthermore, an unwanted excessive number of fruit per tree during that period can reduce the growth of a young tree and delay the achievement of maximum tree size. Because of this, trees require adequate thinning to reach marketable fruit sizes and regular yields by preventing alternate bearing (Maas, 2006). In mature orchards chemical fruit thinning is a major cultural practice (Bound, 2006; Dorigoni and Lezzer, 2007), but in young apple orchards hand fruit thinning is usually done. However, due to the increasing lack of seasonal workers and high labour costs, this job is becoming unrealisable, especially in large areas (Radivojević et al., 2011). Moreover, hand thinning is usually carried out after June-drop, by which time only increases in fruit size are achieved and there is no reduction in alternate bearing (Maas, 2006). Chemical thinning, as compared to hand thinning, is a quick operation and allows thinning fruit at the right moment, guaranteeing better fruit quality and significantly reducing labour costs (Costa et al., 2006). In young apple orchards chemical thinning has to be regularly performed and start in the second leaf, whereby different chemicals can be applied either alone or in combination in order to improve reliability and thinning efficacy (Verjans et al., 2018). Plant growth regulators such as auxins and cytokinins have become essential in commercial apple production (Brunner, 2014; Stern, 2015). However,

Triterpene Content in Flesh and Peel of Apples Grown on Different Rootstocks

“…The largest apple producers in Europe are Poland (25.00%), Italy (19.20%), and France 15.50% [1]. Consequently, apples remain one of the most widely grown and consumed fruits in the world, and their processed products are widely used in the production of food supplements, food industry products, and beverages [2][3][4][5].…”

Optimisation of thinning of apple fruitlets cv. 'Braeburn Mariri Red'

“…In this experiment, combined application of the preparations MaxCel/Brevis produced the best thinning effects through a distinct decrease of yield and improvement of most of the analysed quality parameters of apples, relative to the control. Also Radivojevic et al (2019) demonstrated that the use of a mixture of BA and metamitron can alleviate the unfavourable effect of low temperatures (below 10°C by night and below 20°C in daytime). The application of that mixture caused a significant increase in fruit dimensions and an improvement of yield structure.…”

Metamitron Thinning Efficacy of Apple Fruitlets Is Affected by Different Rates, Timings and Weather Factors in New York State

“…Other authors have reported that the minimum temperature affects metamitron efficacy. Radivojevic et al [46] showed the positive thinning efficacy of a single application at 6-15 mm of metamitron, with minimum temperatures above of 10 • C. Gonzalez et al [2] concluded that, when the average night temperature was higher than 14 • C for 4 days after a single application between 7.5 and 13.5 mm, the efficacy of metamitron was high. Clever [38] estimated that thinning efficacy was higher when the night-time temperature was above 10 • C. However, their results were collected over a different period of days to that of this study (1 day before the spray and 1 or 2 days after the spray).…”