Does primocane management affect raspberry fruit yield or anthocyanin content?

Two herbicides and manual primocane removal were tested for their effects on red raspberry (Rubus idaeus) fruit yield and anthocyanin production. Data were generated in polytunnel-grown 'Glen Ample' near Alyth, Scotland, UK during 2012 and 2013. Herbicides tested were carfentrazone and glufosinate applied up to three times per season, as compared to raspberry plants with primocanes removed by hand up to three times or to plants receiving no primocane removal. Fruit yield, berry weight, and anthocyanin content were determined. Primocane management programs increased average daily raspberry yield by about 7 and 10% in 2012 and 2013, respectively, and total yield of first class fruit by about 9 and 21%, respectively. Individual berry weight tended to increase with the number of times primocanes were removed in 2012, although this trend was less obvious in 2013. Two or three primocane removals resulted in greater daily first class yield in 2012, while three removals increased daily first class yield in 2013. Anthocyanin content of raspberry fruit did not differ by treatment, although there was a trend in the data toward higher anthocyanin content under primocane management programs in both years. Based on these data, growers of 'Glen Ample' in polytunnels should remove primocanes two or three times to maximize production of first class fruit, and may accomplish this using either registered herbicides or by hand removal.