Fruit set and quality responses to artificial spur extinction in planar cordon sweet cherry trees

New planar cordon planting systems of sweet cherry trees (Prunus avium) in closely planted rows (1.5 or 2 m apart) have been designed with the aim of increasing orchard light interception and at least doubling productivity, whilst maintaining high fruit quality. Artificial spur extinction (ASE) is a crop management tool that uses hand-thinning of whole buds and alters floral bud distribution. A trial was established using narrow-row planar cordon 'Sweetheart', 'Lapins' and 'Staccato' cherry trees, to determine whether ASE may be a potential tool for controlling fruit yield, size and quality in this new system. In February 2017, every second bud on two- and three-yearold sections of upright fruiting shoots was removed from replicate whole trees of ASE treatments. Non-ASE treated trees with no bud modification were controls. Flower numbers were estimated on two tagged upright shoots tree(-1) in September 2017 and branch cross-sectional area (BCA) at the shoot base was calculated. Fruit set was calculated from fruit counts made in November 2017 and yields measured at harvest in January 2018. Fruit diameter and soluble solids concentrations (SSC) were measured on a sub-sample. ASE-treated tagged shoots had significantly lower buds numbers cm(-2) BCA than on those from control trees for 'Staccato' but there was no difference for 'Sweetheart' or 'Lapins', possibly due to variability in BCA. This resulted in lower fruit weight cm(-2) BCA on tagged shoots in the ASE treatment for 'Staccato' only. Fruit diameters were similar from ASE and control trees, but SSC was 1% higher in fruit from ASE trees, although non-significant. Tagged shoots on trees at 1.5 m spacing had fewer buds, fewer flowers, fewer fruit and lower total fruit weight cm(-2) BCA than those at 2.0 m spacing. Future trials should be established by setting bud numbers cm(-2) BCA rather than reducing the proportion of buds.