California Agriculture

Production costs in peaches are highly dependent on the cost of labor to prune, thin and harvest trees — costs that would drop if growers had rootstocks that decreased tree size. Collaborating researchers from UC Davis and the U.S. Department of Agriculture’s (USDA) Horticulture Crops Research Laboratory in Parlier screened several promising clonal, size-controlling rootstocks for California peach production. In field tests, two peach scion cultivars (‘Flavorcrest’ and ‘Loadel’) on five interspecific hybrid rootstocks yielded positive results. After 8 years in the orchard, they performed well compared with trees on ‘Nemaguard’ rootstock (the California standard for peaches), with reduced trunk circumferences (60% to 95%), reduced dormant (22% to 80%) and summer (40% to 80%) pruning weights, and acceptable fruit size and crop yields (54% to 98%), since smaller trees will be planted at higher densities. This project has identified three new dwarfing rootstocks with commercial potential for California peach production. One rootstock (‘Hiawatha’) is already available through commercial nurseries and UC and USDA have jointly licensed the two others for commercial use.