The Effects of Chemical Primocane Suppression on Growth, Yield, and Chemical Composition of Red Raspberries1

Abstract

Abstract Primocanes were sprayed after they reached about 18 cm in height with 4, 6-dinitro-o-sec-butylphenol (dinoseb) plus superior spray oil to kill the tops down to ground level. Additional treatments involved spraying after the second flush of growth reached 18 cm in height. Primocane suppression by this means increased yields by up to 70% over unsprayed plots. Plots of vigorous ‘Williamette’ raspberries ( Rubus idaeus L.) were re-sprayed each year for 4 years and maintained the yield increase. A less vigorous ‘Sumner’ planting subjected to similar treatments did not develop adequate cane height and number after 2 or 3 sprays and yields the following year were greatly reduced. Berry size was sometimes increased. Most of the increased yields were due to greater numbers of berries. Primocane suppression had no effect on the number of berries on the upper laterals but greatly increased the numbers on laterals that developed from the middle and lower portions of the canes. The amount of carbohydrates per bud in dormant canes was reduced by dinoseb sprays applied the previous growing season.