Seasonal Effects of a Late Application of Hydrogen Cyanamide on ‘Climax’ Rabbiteye Blueberry

Abstract

A field study was conducted to evaluate the effects of hydrogen cyanamide (H₂CN₂) on flower and leaf buds, foliage, and fruit of ‘Climax’ rabbiteye blueberry (Vaccinium ashei, Reade), a cultivar exhibiting erratic spring foliation following mild winters. Stems of ‘Climax’ in several stages of flower bud development were sprayed with H₂CN₂(0, 1.0, 1.5 and 2.0% v/v), and effects on leaf development, injury to flower buds, and fruit development were studied. H₂CN₂ increased rate of vegetative bud opening, terminal leaf area, and overall leaf canopy. Flower bud injury was excessive when H₂CN₂ was applied at rates > 1.5% v/v or when flower buds were at stages 4-5 of development; 1.5% H₂CN₂ significantly reduced yield and rendered berries more susceptible to late spring frost injury. H₂CN₂ dramatically increased total number of vegetative buds developed for the next season's foliage, delaying bud break in the Spring of 2001. Results of this study agreed with similar controlled environment studies in that when H₂CN₂ was applied at rates not exceeding 1.0% v/v and before a majority of flower buds exceed development stage 2, vegetative bud development was enhanced and damage to flower buds was minimal.

Key Words:

• Vaccinium ashei
• 'Climax'
• hydrogen cyanamide