Timing and Concentration of Hydrogen Cyanamide Affect Blueberry Bud Development and Flower Mortality

Abstract

<jats:p>The effects of hydrogen cyanamide (H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub>) sprays on vegetative and reproductive bud growth and development were evaluated for `Climax' rabbiteye (<jats:italic>Vaccinium ashei</jats:italic> Reade) and `Misty' southern highbush blueberry (<jats:italic>V. corymbosum</jats:italic> L. hybrid). `Climax' plants were sprayed with 0% or 1% H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub> (v/v) at each of several time intervals or flower bud growth stages following either 270 or 600 hours of artificial chilling. `Misty' plants were sprayed with 0%, 1%, or 2% H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub> (v/v) immediately after exposure to 0, 150, or 300 hours of artificial chilling. H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub> application to `Climax' plants at 3 days after forcing (DAF) and at 10% to 30% stage 3 flower bud development dramatically accelerated leafing, and only minimal flower bud damage was observed at these application times. For `Misty', vegetative budbreak was increased and advanced by both H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub> spray concentrations, regardless of pretreatment chilling levels; the number of vegetative budbreaks per plant increased with increased concentration. Timing of anthesis did not appear to be affected by H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub>, but fruit maturity was hastened. Increased pretreatment chilling also hastened fruit development. This effect on maturity appears to be due primarily to increased and accelerated vegetative budbreak, which probably increased leaf: fruit ratios. Greater flower bud mortality from H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub> occurred in nonchilled plants than in those chilled for 150 or 300 hours, especially at 2% H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub>. These results indicate that H<jats:sub>2</jats:sub>CN<jats:sub>2</jats:sub> has potential value in stimulating vegetative bud development, which potentially hastens maturity in blueberries grown under the mild winter conditions of the Southeast. However, spray concentration and timing of application will be critical to successful use of this compound.</jats:p>

Evaluation of Flower Bud Removal Treatments on Growth of Young Blueberry Plants

“…The numbers of lateral vegetative budbreaks per centimeter of shoot length were increased by hydrogen cyanamide sprays for both cultivars and in both years (Tables 1-3). This result was expected and is consistent with known responses of southern highbush blueberry to hydrogen cyanamide (Williamson et al, 2001(Williamson et al, , 2002. In Expt.…”

“…Hydrogen cyanamide has been used in blueberry production in the southeast United States to stimulate leaf growth and advance the ripening date of blueberries Williamson et al, 2001Williamson et al, , 2002. During these earlier experiments, observations revealed that poorly timed hydrogen cyanamide applications resulted in significant flower bud mortality, even though leaf growth was readily stimulated.…”

‘Rebel’ Southern Highbush Blueberry

“…Emergence of 'Rebel' leaves has been excellent, even after mild winters. This is important because many southern highbush blueberries grown in the low-chill areas of the southeastern United States have poor leaf development (Lyrene and Williamson, 1997;Williamson et al, 2001). 'Rebel' plants are highly branched, producing an abundance of fruiting wood.…”

Use of Plant Growth Regulators in Blueberry Production in the Southeastern U.S.

“…Dormex™ (50% hydrogen cyanamide) has shown potential in accelerating leaf and floral bud development of some fruit crops; so research was conducted to determine its usefulness on blueberries (Williamson et al, 2001(Williamson et al, , 2002. Table 10 shows results from an experiment that was conducted to examine the effects of timing of Dormex applications on 'Climax' rabbiteye blueberry (Williamson et al, 2001).…”

“…Table 10 shows results from an experiment that was conducted to examine the effects of timing of Dormex applications on 'Climax' rabbiteye blueberry (Williamson et al, 2001). Plants were artificially subjected to low (270 hrs below 7°C) and moderate (600 hrs below 7°C) chilling conditions and were placed under greenhouse conditions to force vegetative and floral buds.…”