ABSTRACT
No injury to flower buds was detected in any cultivar at either H2CN2 application timing (data not shown). Results of observations on vegetative bud development for the respective blueberry cultivars are presented in Figures 1-4. At each application timing, the 1.0% H2CN2 treatment resulted in increased rate of vegetative bud development in each of the four blueberry cultivars when compared to 0% H2CN2. Mean bud stage ratings observed on the last evaluation dates indicated that when H2CN2 was applied at the point at which cultivars had accumulated 50% of their chill hour requirement the vegetative bud ratings of ‘Bladen’, ‘Jubilee’, ‘Premier’, and ‘Tifblue’ advanced by 0.2, 0.4, 0.5, and 0.7 stages, respectively. H2CN2 applications made when these cultivars had accrued 75% of their chill hour requirements resulted in physiological development rating increases of 0.9, 1.0, 1.0, and 1.2, respectively. Comparing the 50% CHA, 1.0% H2CN2 application to the control (100% CHA, 0% H2CN2) at these evaluation dates, bud development ratings of the respective cultivars differed by —0.1,0.4,0.3, and
0.3 stages. At 75% CHA + H2CN2, advances in bud development were substantially greater with rating increases of 1.9, 2.2, 1.5, and 1.0, respectively, over that of the control. Results of this study demonstrated that 1.0% H2CN2 applied to blueberry cultivars having artificially accrued 75% of their chill hour requirements, advanced vegetative bud development to a greater extent than applications at 50% CHA. This same treatment generated even greater vegetative bud development than that observed on cultivars having accrued 10 0% of their chill requirement, but lacking a supplemental H2CN2 application.
