Blueberry Flower Bud Removal Using Hydrogen Cyanamide

Commercial blueberry growing practices for many states includes flower or fruit
removal for the first one or two growing seasons in order to reduce plant stress associated with maintaining a crop load.  This is typically accomplished by hand stripping flower buds after planting during the spring, or pruning shoots having flower buds prior to planting.  To investigate an alternative to current laborious flower bud removal practices, the effectiveness of hydrogen cyanamide applications on flower bud removal of young rabbiteye (Vaccinium ashei Reade) blueberry plants was evaluated.   The treatments consisted of no flower bud removal (control), hand stripping, and two rates of hydrogen cyanamide (0.75% and 1.5%).  Treatments were applied to three different cultivars exhibiting different stages of flower bud development.  The cultivars, listed from most advanced to least advanced flower bud development were ‘Climax’, ‘Brightwell’, and ‘Tifblue’, respectively.  Both hydrogen cyanamide rates (0.75% and 1.5%) resulted in flower bud mortality.  However, hydrogen cyanamide applied at a rate of 1.5% removed flower buds as effectively as the hand stripping treatment.  No visual phytotoxicity was observed as a result of hydrogen cyanamide application.  The range of flower bud stages present at the time of hydrogen cyanamide application did not affect flower bud mortality.  The leaf area of ‘Climax’ and ‘Tifblue’ cultivars was not affected by treatments, whereas hydrogen cyanamide treatments resulted in a greater leaf area of ‘Brightwell’.   Based on results from the first year of this study, hydrogen cyanamide applied at the rate of 1.5% appears very effective at removing flower buds on young blueberry plants.  This method of flower bud removal may provide a labor-saving alternative to hand thinning or pruning for commercial rabbiteye blueberry establishment.