Budburst and yield of ‘Peeka’ apricot influenced by time and concentration of hydrogen cyanamide application

Abstract

The rest-breaking response of ‘Peeka’ apricots (P. armeniaca L.) grown locally under conditions of inadequate winter chilling to 0%, 0.25%, 0.5%, 0.75%, and 1% hydrogen cyanamide sprayed 29 July, 3 August, 13 August, and 17 August 1987 is reported, owing to renewed interest in this chemical following the recent withdrawal of dintro-ortho-cresol (DNOC). These dates ranged from ca. 7 to 4 weeks before reproductive budburst of the control (15 September), and covered the perceived optimum spray period. Vegetative budburst increased with rate and time of hydrogen cyanamide application and was highest with 0.75% hydrogen cyanamide sprayed on 13 August. Reproductive budburst also increased with rate reaching a maximum with the 13 August applications. Yield increased with rate up to 1% hydrogen cyanamide and was also time dependent. Highest yield was obtained with the 3 August application, one week earlier than the optimum date for budburst on 13 August. These results from one season confirm the occasional observation of disappointing fruit set following intense blossom after the application of hydrogen cyanamide. Additional data are required to predict application dates to optimise fruit set.