Mechanical Canopy Management Reduces Labor Costs and Maintains Fruit Composition in 'Cabernet Sauvginon' Grape Production

Three canopy management methods, hand pruning (HP), mechanical prepruning with hand shoot thinning (MP+HT), and mechanical box-pruning with mechanical shoot thinning (MP+MT), were applied with the objective of achieving similar and commercially marketable ‘Cabernet Sauvignon’ grape (Vitis vinifera) yields while maintaining vine balance and comparing labor operations costs. Canopy management system labor operation cost estimates indicated a 62% and 80% labor savings with the MP+HT and MP+MT treatments, respectively when compared with HP. The total shoot density of the vines was unaffected by the treatments applied. However, the contribution of count shoots increased with the concomitant addition of mechanization to canopy management. All treatments achieved similar canopy architecture and microclimate. The treatments did not affect photosynthetically active radiation (PAR) intercepted in the fruiting zone of canopy at veraison. All treatments had similar yield, total soluble solids (TSS), juice pH, and titratable acidity (TA) at harvest. Berry skin total phenolics, anthocyanins, and tannins when measured at harvest were also similar among the treatments applied. All treatments tested were within acceptable Ravaz index limits of 5 to 10 lb/lb. However, only MP+MT treatment reached a near optimum leaf area to fruit ratio of 1.2 m²·kg⁻¹ and pruning weight of 1.0 kg·m⁻¹ for warm climate viticulture. The results of this study provide commercially acceptable mechanical canopy management options that may provide labor cost savings for winegrape growers in California's San Joaquin Valley.