2017 ASHS Annual Conference

Most floricane red raspberry (Rubus idaeus L.) plantings in the Pacific Northwest are caneburned. Caneburning is removing the first-emerging primocanes with herbicides in early spring in attempt to reduce their competition with floricanes during flowering and fruiting and thereby increase fruit yield. Two-year trials were conducted in maritime northwestern Washington and in semi-arid central Washington to determine how carfentrazone, oxyfluorfen, or saflufenacil applied for primocane management affect fruit quality and cane growth in a total of five red raspberry cultivars. Additionally, total nonstructural carbohydrate content was characterized for ‘Meeker’ and ‘Chemainus’ primocanes and laterals grown at both locations. While berry and cane parameters were not affected by herbicide treatment at either location, many did differ by cultivar and location (central vs. western Washington sites). Anthocyanin content was generally greater in western Washington fruit, although °Brix and polyphenol content were higher in central Washington. In central Washington, ‘Wakefield’ fruit were higher in anthocyanin content and lower in pH than ‘Chemainus’ or ‘Meeker’. Across cultivars, midseason floricane and fruiting lateral biomass was 2.2 and 1.7 times greater, respectively, in northwestern Washington than in central Washington, while the opposite was true for primocanes (13% more biomass in central Washington). Among the three cultivars in central Washington, ‘Wakefield’ produced more primocane and fruiting lateral biomass than ‘Meeker’ or ‘Chemainus’, particularly in 2016. There were few large differences in cane biomass among the four cultivars in western Washington, except for the 16% lower floricane biomass of ‘Meeker’ compared to the other cultivars in 2016, and the 35% to 60% lower lateral biomass in ‘Cascade Bounty’ in 2016 and ‘Chemainus’ in both years compared to ‘Meeker’ and ‘Saanich’. When data were pooled across location and years, ‘Meeker’ primocanes contained greater carbohydrate concentrations than ‘Chemainus’. Carbohydrate content of ‘Chemainus’ fruiting laterals was greater than in ‘Meeker’ in central Washington, while ‘Meeker’ fruiting lateral carbohydrate concentration exceeded that of ‘Chemainus’ in western Washington. Based on these data, cultivar choice and environmental factors (e.g., location) significantly affected aspects of red raspberry fruit quality, cane growth, and cane carbohydrate content, while caneburning programs did not.