Performance of Mechanical Thinners for Bloom or Green Fruit Thinning in Peaches

Abstract

<jats:p>Peach (<jats:italic>Prunus persica</jats:italic> L. Batsch) thinning is a costly and time-consuming but necessary practice to produce a crop of marketable size fruit. A number of mechanical devices and methods have been developed and evaluated to reduce the cost and time required for hand thinning peach. This report provides additional evidence that a Darwin string thinner can effectively thin peach at bloom and a spiked drum shaker can thin at bloom or at the green fruit (pit hardening) stage. Five trials were conducted over 2 years in grower orchards with trees trained to a perpendicular V system. A Darwin string thinner at 60% to 80% full bloom (FB) reduced crop load (fruit/cm<jats:sup>2</jats:sup> limb cross-sectional area) on scaffold limbs by 21% to 50% compared with a hand-thinned control. At the 60% FB stage, a USDA-designed double-spiked drum shaker reduced crop load by 27% and in another trial, a USDA prototype single-drum shaker reduced crop load by 9%. Across all trials, the spiked drum shakers (single or double units) removed an average of 37% of the green fruit. All mechanical devices reduced the time required for follow-up hand thinning. Follow-up hand-thinning costs (US$/ha) were reduced an average of 27% by mechanical thinning devices over hand-thinned control trees. Fruit size was increased over hand-thinned controls by mechanical thinning in most, but not all, trials. A combined treatment of the Darwin string thinner at bloom followed by a drum shaker (single or double unit) at the green fruit stage produced the greatest net economic impact in a number of the trials. Despite overthinning in some trials, the mechanical thinning devices described provide a potential alternative to hand thinning alone in peach production.</jats:p>

Laboratory Device to Assess the Effect of Mechanical Thinning of Flower Buds, Flowers and Fruitlets Related to Fruitlet Developing Stage

“…The number of flower buds, flowers, or fruitlets registered along the weeks reduced drastically after week 7, which was related to the natural thinning of the tree in 2017 season ( Figure 5). Agronomy 2019, 9,668 7 of 11 Retention force evolution was very similar to mass. However, retention force was one week ahead of the mass, starting to drastically increment in the seventh week.…”

“…Mechanical thinning has been tested in peaches using inertial trunk shakers and electromagnetic shakers [6,7]. Besides, in stone fruits and pome fruits, flower and fruit thinning has been studied using drum shakers [8][9][10]. The studies proved that mechanical thinning saves time and reduces thinning cost.…”

The use of agricultural robots in orchard management

“…Even when chemical thinning is performed, green fruit thinning is necessary and done manually in many fruit species after the threat of frost is past, and in some cases with a mechanical thinner (Miller et al 2011). However, there are no efforts reported in the literature to date concerning robotic approaches to the green fruit thinning problem, neither green fruit detection nor its removal.…”

Evaluation of a New Machine for Flower and Fruit Thinning in Stone Fruits

“…Mechanical thinning could represent an economically and/or environmentally sustainable alternative to manual and chemical thinning in fruit trees. Several studies demonstrated that mechanical thinning is a viable method for initial crop load reduction, provided that follow-up hand thinning to reach optimal crop load and distribution of fruit in the canopy is contemplated [21][22][23]. Mechanical thinning can reduce the manual thinning requirement from 40% to 100% [8,11,14].…”

“…Mechanical thinning can reduce the manual thinning requirement from 40% to 100% [8,11,14]. Over the years, a number of thinning devices, with constructively and functionally different operative systems, have been tested on peach and, to a lesser extent, on apricot [24], including hand-held devices [25], trunk shakers [12], spiked drum canopy shakers [2,8,22], frequency electrodynamic limb shakers [9,26]. String thinner devices such as the German-designed Darwin ® or similar machines operating with a rotating rope curtain [8,11,23,27,28] have been quite successfully tested on peach orchards trained to narrow canopy systems, for example, Central leader or perpendicular V, reducing the manual thinning requirement [8,23].…”