Initial Response of ‘Concord’ and ‘Sunbelt’ Grapes to Pruning and Fruit Thinning

Abstract

Balanced, dormant hand pruning was compared with minimal and machine box-cut pruning with no fruit thinning, thinning at 27 to 45 days postbloom, or thinning at veraison on Vitis labruscana grape cultivars, Concord and Sunbelt. Weekly berry weights measured during the growing season showed that minimally pruned ‘Concord’ and ‘Sunbelt’ generally had lower berry weights than hand-pruned vines. Lag phase occurred 50 ± 7 days postbloom in ‘Concord’ and 58 ± 7 days postbloom in ‘Sunbelt’. The duration of harvest period was longer for ‘Concord’ than ‘Sunbelt’, and minimally pruned vines without thinning had the most delayed ripening regardless of cultivar or time of fruit thinning. The desired soluble solids of 17% for ‘Concord’ and 18% for ‘Sunbelt’ were achieved without differences in other fruit composition parameters on all treatments. Delaying harvest of minimally pruned vines without thinning by about 7 days was required to achieve the desired soluble solids. Pruning methods had more effect on yield components than time of thinning. At harvest, minimally pruned vines had lower cluster weights, berry weights, and yield per node compared with hand pruning in both cultivars and years. In terms of second year yield response, ‘Sunbelt’ was not as detrimentally impacted by machine and minimal pruning without thinning compared with ‘Concord’. Preliminary results indicate that machine and minimal pruning with and without thinning are viable alternatives to hand pruning for ‘Concord’ and ‘Sunbelt’ grapes in irrigated vineyards with warm, long growing seasons.