The Effect of Timing of Dormex Application on Blueberry Leafing and Flower Mortality

Abstract

Leaf bud development is a problem on many blueberry cultivars grown throughout the Southeast. Dormex (50% hydrogen cyanamide) has shown potential in accelerating leaf and floral bud development of some fruit crops, but its usage on blueberries has not been thoroughly explored. A greenhouse experiment was conducted to examine the effects of timing Dormex applications on `Climax' rabbiteye blueberry (Vaccinium ashei) and `Oneal' southern highbush blueberry (V. corymbosum). Plants were subjected to low and moderate chilling conditions and were forced under greenhouse conditions. Dormex timings were: 1)1 day after forcing (DAF), 2) 3 DAF, 3) at 10% stage 3 floral buds, 4) at 30% to 50% stage 3 floral buds, 5) at 10% to 30% stage 4 floral buds, 6) control (no Dormex). All Dormex applications were applied at a rate of 2% product. Results showed that Dormex both increased and accelerated leaf bud break as compared to the control. However, flower buds at stage 3 of development or beyond were very susceptible to chemical burn by the product. The data indicate that timing of Dormex applications on blueberries should be based on rate of plant development rather than calendar time. Additional research is needed to most effectively use the product to aid blueberry leaf development.