Effects of hydrogen cyanamide in manipulating budburst and advancing fruit maturity of table grapes in south-eastern Queensland

Four times of winter pruning and hydrogen cyanamide application were evaluated for their effects on budburst, growth, flowering and yield of the table grape cultivar Muscat Hamburg in south- eastern Queensland (lat. 26°S.). Hydrogen cyanamide hastened budburst at all times of application. When cyanamide was applied 8-10 weeks before natural bud-burst, fruit maturity was advanced by 14-18 days, However, application within 4-6 weeks of natural bud-burst had little or no effect on time of fruit maturity. Low temperatures during flowering, which can adversely affect pollination, seed development and hence yield, may limit the use of early pruning and cyanamide application, particularly under cooler subtropical conditions. Depending on market prices, any loss of yield associated with early pruning and cyanamide applications will need to be compensated for by higher prices received for earlier maturing fruit. Cyanamide may have greater commercial potential for use on young, vigorous vines growing under warm subtropical conditions. Under these conditions, cyanamide application at 4-6 weeks before natural budburst gave significant yield increases by increasing the number of bunches produced per spur. No deleterious effects of cyanamide on fruit quality were recorded.