Growth and Fruiting of ‘Heritage’ Primocane Fruiting Red Raspberry in Response to Daminozide and Ethephon

Abstract

Abstract Butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) (2000 and 4000 ppm) was applied to ‘Heritage’ primocane fruiting red raspberry (Rubus idaeus L.) primocanes at combinations of several dates, when the canes averaged 19, 42, 65, and 79 or 91 cm in height. Daminozide-treated plots achieved 50% of the eventual final yield an average of 8 days earlier (averaged for 5 treatments involving daminozide application at 42 cm) than controls. This advance of the production curve resulted in an average yield increase of 51% during the first 28 days of production. However, while early yields were increased, total yields were unaffected. Increasing the concentration of daminozide from 2000 to 4000 ppm did not increase the effects. Double application of daminozide (2000 ppm) at 65 and 79 cm and single application at 91 cm reduced yield during the 14 to 28 day harvest period compared to that of the single 65 cm application. This reflects, in part, the reduced berry size during the early harvest period resulting from the later (79 or 91 cm) applications of daminozide. Daminozide reduced the number of nodes formed and advanced the date of anthesis. Application of (2-chloroethyl)phosphonic acid (ethephon) (300 ppm at 19 and 42 cm) increased the number of nodes formed, delayed anthesis by about 13 days, delayed fruiting, and reduced total production.