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In Chile, apple chemical thinning uses primarily carbaryl, which is expected to be banned in the future. New thinning chemicals are needed. During the 2013-14 season, two trials were conducted in a 'Brookfield Gala'/Pajam 2 orchard. Metamitron (Goltix Compact(MR) 90% WG, 450 g ai ha-1) or BA (Exilis®, 180 g ai ha-1) plus NAA (NAA 800®, 18 g ai ha-1) were evaluated at different timings beginning at 4 mm up to 28 mm fruit diameter at 3 to 8 day intervals. Control treatments included, one without any spray and a sprayed control that included NAA at full bloom, carbaryl (Carbaryl 85 WP, 1368 g ai ha-1) at petal fall and BA (180 g ai ha-1) plus carbaryl (1368 g ai ha-1) at 12 mm fruit. All sprays were done when no carbohydrate deficit was predicted by Malusim Model (Cornell University). Thinning was evaluated on two branches tree-1, fifty days after full bloom, as fruits per cluster (F/C). All treatments differed from the control (2.3 F/C). Metamitron treatments were more effective when applied between 8 and 16 mm fruit (1.0 F/C). NAA+BA treatments were more effective when applied right after petal fall (4 mm fruit; 1.3 F/C). After removing the effect of crop load, average fruit weight was increased with BA+NAA spray at 4 and 12 mm fruit. All treatments of metamitron were different from the control.

The study was conducted on two consecutive seasons (2007-2008 and 2008-2009) to determine if crop load adjustment and cluster tipping in relation to cluster shape can allow an increase in cluster weight and yield per plant in ‘Thompson Seedless’ table grapes. During the first season the feasibility to classify clusters – prior to cluster thinning – as cylindrical, spherical or conical, was evaluated. Once feasibility was validated a crop load experiment was conducted, regulating crop load depending on the percentage of cylindrical clusters. Additionally, a cluster-tipping trial combining crop load with cluster shape and berry number was carried out. Results indicated that ‘Thompson Seedless’ plants with higher percentage of cylindrical clusters have lower yields; increasing cluster number per plant and berry number per cluster increase yield; and spherical and conical clusters on ‘Thompson Seedless’ present greater berry weight and size. These results can benefit ‘Thompson Seedless’ table grape vineyards management to optimize crop load adjustment in relation to yield and grape quality.