Application Techniques Alter Uniconazole Efficacy on Chrysanthemums

Four experiments using container-grown Dendranthema ×grandiflorum (Ramat.) Kitamura 'Nob Hill' or 'Tara' were conducted to determine effects of application site and spray volume on uniconazole efficacy. Uniconazole applied only to mature leaves was less effective in controlling stem elongation than were stem applications, whole-plant sprays, or medium drenches. Spray volume altered efficacy more for uniconazole than for daminozide. Also, the effect of uniconazole spray volume was greater when the medium was not covered than when covered to prevent spray solution entering medium. Results from these studies showed the efficacy of uniconazole increased with increased stem coverage andwith amount of chemical reaching the medium, which was achieved with high spray volumes. Chemical names used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol- 1-yl-1-penten-3-ol) (uniconazole); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide). important with uniconazole also; however, this potential has not been adequately investi- gated. Bailey (1989) reported that uniconazole spray volume was not a factor when concen- tration was varied to give the same active ingredient per plant. Gilbertz (1992) demon- strated that paclobutrazol and uniconazole had greater efficacy if applied soon after pinching, when there would be less leaf coverage of the medium, compared to later applications. Materials and Methods We examined the effects of spray volume, timing, and application site on uniconazole efficacy for reducing growth of chrysanthe- mums. Four experiments were conducted us- ing rooted cuttings planted in Vergro Klay Mix (Verlite Co., Tampa, Fla.). This medium does not contain pine bark, which reduces efficacy of triazole drench treatments (Barrett, 1982). Plants were fertilized at every watering