CHRYSANTHEMUM RESPONSE TO TIMING OF PACLOBUTRAZOL AND UNICONAZOLE SPRAY APPLICATION

in HortScience
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  • 1 University of Georgia, Department of Horticulture, Georgia Station, Griffin, GA 30223

Spray applications of uniconazole (UC) or paclobutrazol (PB) were applied 0, 2, or 4 weeks after pinching Dendranthema grandiflora (Tzvelev). `Bright Golden Anne' cuttings planted 4 per 15 cm pot. Cuttings were controlled to 3 shoots each, averaging 5.4 and 14.9 cm at 2 and 4 weeks, respectively.

Final height was affected interactively by week of application and chemical treatment. Treatment at pinch caused less stem elongation than later treatments, probably due to persistence of PB and UC activity until flowering. At week 4, 67% of stem elongation had already occurred and, therefore, less retardation was possible. Of the 4 triazole treatments, PB at 30 mg 1-1 (20 ml per pot) applied at pinch produced heights similar to daminozide 5000 mg 1-1 applied at 2 weeks. PB at 60 mg 1-1 gave similar height control as UC 15 mg 1-1. UC 30 mg 1-1 treated plants were shortest regardless of treatment timing, averaging 16.9 cm applied week 2.

Other growth data was pooled for week of application and for chemical treatment since there was no interaction. Flowering was delayd 2 days and flower dry weight was reduced up to 26% by treatment at pinch compared to later treatments. Flower diameter was only minimally affected by treatments.

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