Masters Theses

Gok Yin Yeow

Date of Award

3-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Landscape Architecture

Major Professor

Gary L. McDaniel

Committee Members

Effin T. Graham, Hendrik van de Verken

Abstract

The experimental growth retardant, uniconazole, Sumagic™ [(E)-(p-chlorphenyl)-4,4,-dimethyl-2-(1,2,4-triazol-l-yl)-l-penten-3-ol] was evaluated for growth control on several bedding plant species, chrysanthemum, poinsettia, and Easter lily cultivars. Uniconazole was compared against chlormequat [(2-chloroethyl) tri-methylammonium chloride], daminozide [succinic acid-2, 2-dimethyl-hydrazide], or ancymidol [α-cyclopropyl , α-4-methoxypropyl , α-5- pyrimidine methanol] for effectiveness in controlling height on the various test species. Uniconazole foliar spray concentrations of 5-60 mg/1 severely retarded growth of several bedding plant species, especi-ally geranium and coleus. Optimum growth control was at 4 mg/1 or below. Delay in flowering occurred in all bedding plants tested, except for geranium and coleus, which exhibited earlier flowering. Soil drenches of uniconazole were more active than foliar sprays for 'Annette Hegg Dark Red' and 'Gutbier V-14 Glory' poinsettias, and 'Bonnie Jean' chrysanthemum. Best growth control was achieved by foliar sprays at 5 mg/1 or below. Higher concentra-tions of uniconazole severely retarded plant growth regardless of application methods. Uniconazole as bulb soaks prior to cooling severely reduced growth of 'Ace' and inhibited shoot emergence of 'Nellie White' Easter lilies. Postemergence soil drenches and foliar sprays were less effective in controlling growth than were bulb-soaks. Best finished plants for both of these cultivars were observed at 5-10 mg/1 sprays and 2-3 mg/pot drenches. All soak treatments (2-10 mg/1) retarded growth severely, especially for 'Nellie White'. There was a trend toward delayed emergence and flowering with in-creasing uniconazole concentrations when applied as bulb-soaks. However, no significant delays in flowering occurred either from soil drench or foliar spray treatments. Severe leaf phytotoxicity was observed in all foliar spray treatments of uniconazole, but this was not observed on drench and soak treated plants.

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