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Thomas J. Banko and Marcia A. Stefani

Russian sage (Perovskia atriplicifolia) grown in a pine bark medium in 1-gal containers were sheared to a height of 15 cm on 20 June 1997. One day later the plants were treated with foliar sprays of Florel (ethephon) at 0, 500, or 1000 ppm. One week later, sprays of B-Nine (daminozide, 5000 ppm) or Sumagic (uniconazole, 15 ppm) were applied to some of the plants previously treated with Florel, or previously nontreated. Three weeks after initial treatments, the Florel (500 and 1000 ppm) and the Sumagic treatments, applied individually, reduced plant height by 26%. The B-Nine treatment reduced height by 18%. Combination treatments (Florel followed by Sumagic or Florel followed by B-Nine) provided additional height control Florel at 500 or 1000 ppm significantly increased branching of Perovskia. Additional treatments with B-Nine or Sumagic had little effect on this response. Florel delayed flowering by ≈7 to 10 days.

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James L. Gibson and Brian E. Whipker

Twenty-six ornamental cabbage and kale (Brassica oleracea var. acephala) cultivars were grown in 8-inch (20.8-cm) diameter pots during Fall 1998 to classify their foliage traits and determine their response to the plant growth regulator (PGR) daminozide. Cultivar vigor was classified by height. Foliage characteristics were described and cultivars of ornamental cabbage, notched ornamental kale, and curly ornamental kale were selected for retail or wholesale markets based on the shortest number of days until a significant center color change, the largest center color diameter, and attractive foliage characteristics. Two cultivars treated with 2,500 ppm (mg·L-1) daminozide and eight cultivars treated with 5,000 ppm were significantly smaller in height compared to nontreated plants. Plants were treated 6 weeks after sowing, and the response to the PGRs may have been diminished by the age of the plant. Therefore, to further investigate PGR efficacy, seven outstanding cultivars selected in 1998 were treated with 5,000 ppm daminozide or 5 ppm uniconazole 14 days after potting (4 weeks after sowing) in Fall 1999. Greater control was observed with daminozide at 5,000 ppm in 1999 with a 13% smaller plant height as compared to 9% in 1998, when compared to the nontreated control. For greater height control, PGR applications to ornamental cabbage and kale should be applied 4 weeks after sowing.

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Harry K. Tayama and Stephen A. Carver

Residual activity of a single uniconazole spray (15 mg a.i./liter), uniconazole drench (600 μg a.i./pot), and daminozide spray (5000 mg a.i./liter) were compared to an untreated control using the `Bright Golden Anne' chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitamura]. Based on weekly internode growth, spray and drench treatments with daminozide and uniconazole remained active for 2 to 2.5 and 3 to 3.5 weeks, respectively. Chemical names used: butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); (E)-1-(p-chlorophenyl)-4,4-diemethyl 1-2(1,2,4-triazol-2-yl)-l-penten-3-01 (uniconazole).

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Kenneth C. Sanderson, Durward A. Smith, and John A. McGuire

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James L. Gibson and Brian E. Whipker

Ornamental cabbage and kale (Brassica oleracea var. acephala) plants of cultivars Osaka White and Nagoya Red were treated with paclobutrazol and uniconazole as foliar sprays or substrate drenches. These treatments were compared to the industry standard of daminozide foliar sprays. Applying drenches of paclobutrazol (a.i.) at 4 mg/pot or uniconazole (a.i.) at 1 mg/pot (28,350 mg = 1.0 oz) resulted in 6% or 17%, respectively, shorter `Osaka White' plants while a 2 mg/pot paclobutrazol drench or a uniconazole drench at 0.25 mg/pot resulted in 25% shorter `Nagoya Red' plants. Although effective, the expense of substrate drenches for both plant growth regulators (PGRs) would not be economically feasible for growers to use. Paclobutrazol foliar sprays at concentrations of up to 80 mg·L-1 (ppm) were ineffective in controlling plant height and diameter of either `Osaka White' or `Nagoya Red'. A uniconazole foliar spray of 16 mg·L-1 resulted in 17% shorter `Nagoya Red' plants and 6% shorter `Osaka White' plants. A daminozide foliar spray of 2500 mg·L-1, sprayed twice, resulted in 21% shorter plants for both cultivars. Spraying daminozide would provide optimal height control for the retail grower. Although spraying daminozide twice controlled plant height and costs half the amount of an uniconazole spray at 16 mg·L-1, plant diameter was not affected with daminozide, therefore a wholesale grower who would desire a smaller diameter plant should use a uniconazole spray of 16 mg·L-1.

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James L. Gibson and Brian E. Whipker

Vigorous osteospermum (Osteospermum ecklonis) cultivars Congo and Wildside received foliar sprays of daminozide or daminozide + chlormequat (Expt. 1). Both cultivars responded similarly to the plant growth regulator (PGR) treatments. Only a limited amount of plant height control occurred using 5,000 mg·L-1 (ppm) daminozide + 1,500 mg·L-1 chlormequat or 5,000 mg·L-1 daminozide + 3,000 mg·L-1 chlormequat. Flowering was delayed, phytotoxicity was observed, while peduncle length increased, suggesting that higher concentrations of daminozide or chlormequat may or not be effective at any concentration and may result in increased phytotoxicity. In Expt. 2, `Lusaka' received foliar sprays or substrate drenches of paclobutrazol or uniconazole. Foliar sprays ≤80 mg·L-1 paclobutrazol or ≤24 mg·L-1 uniconazole were ineffective in controlling plant growth. Substrate drenches of paclobutrazol (a.i.) at 8 to 16 mg/pot (28,350 mg = 1.0 oz) produced compact plants, but at a cost of $0.23 and $0.46/pot, respectively, would not be economically feasible for wholesale producers to use. Uniconazole drenches were effective in producing compact `Lusaka' osteospermum plants. Uniconazole drench concentrations of 0.125 to 0.25 mg/pot were recommended for retail growers, while wholesale growers that desire more compact plants should apply a 0.25 to 0.5 mg/pot drench. Applying uniconazole would cost $0.06 for a 0.25 mg drench or $0.12 for a 0.5 mg drench.

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Gary J. Keever and William J. Foster

`Redwings' and `Gloria' azaleas (Rhododendron × `Redwings' and `Gloria') were treated with foliar sprays of uniconazole, paclobutrazol, or daminozide to suppress bypass shoot development and promote flower initiation and development. Uniconazole at 5 and 25 mg·liter-1 suppressed bypass shoot development of `Redwings' and `Gloria', respectively. Flowering of `Gloria', but not `Redwings', was delayed slightly with uniconazole sprays up to 25 mg·liter-1 ; with the highest uniconazole concentration, 200 mg·liter-1, flowering was delayed as much as 18 days. Flower count of `Gloria' was not affected by lower concentrations of uniconazole, but it was greatly reduced in both cultivars with concentrations above 75 mg·liter-1. Uniconazole was more active than paclobutrazol sprays of similar concentrations or than two daminozide sprays of 3000 mg·liter–1 . Chemical names used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole); (2RS,3RS)-1-(4-chlorophenyl)-2-(1,1-dimethylethyl)-(1H-1,2,4,-triazol-l-yl-)pentan-3-ol (paclobutrazol); butanedioic acid mono(2,2-dimethylhydrazide (daminozide),

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Hiroshi Iwanami, Nobuyuki Hirakawa, Hiroyasu Yamane, and Akihiko Sato

Crosses between seedless cultivars had been conducted to produce seedless table grape efficiently by combining with ovule and embryo culture in Vitis vinifera L. But very few plants grew normally in this method. Four plant growth regulators (Cycocel, B-Nine, Uniconazole-P, Ethrel) were applied to shoots 4 weeks before anthesis to develop the seeds of two seedless cultivars `Flame seedless' and `A1706'. Correlation was significant in each cultivar between the shoot length at anthesis and the number of seed traces per berry in all combined treatments. Analysis of covariance revealed that the number of seed traces per berry was significantly higher when the shoots were applied with Uniconazole-P (240 ppm) than B-nine (2000 ppm), Cycocel (500 ppm) and Ethrel (400 ppm) in `Flame seedless' and Uniconazole-P and B-nine than Ethrel in `A1706'. Ovules of these two seedless cultivars crossed with seedless cultivar `Perlette' after the application of four plant growth regulators were cultured on half-strength MS medium with 10 μm IAA and the percentage of developed embryos in ovules was higher when the shoots were applied with Uniconazole-P and B-nine than Cycocel, Ethrel in `Flame seedless' and B-nine than others in `A1706'. These results indicate that the use of certain plant growth regulators promotes the embryo development.

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Johnny Carter and Edwin K. Mathews

Paclobutrazol and three commercial growth retardants (B-nine, Cycocel and A-rest) were compared for their effectiveness in controlling the growth of five bedding plant species ('Yellow Boy' marigold, `Blue Blazer' ageratum, `Dreamland Orange' zinnia, `Better Boy' tomato and `Black Beauty' eggplant). Results showed that growth suppression depended on the treatment and species tested. All of the growth retardants suppressed the growth of `Yellow Boy' marigold. Growth of `Blue Blazer' ageratum was suppressed by all the treatments except for Cycocel. With `Dreamland Orange' zinnia, B-nine and Cycocel suppressed growth while Paclobutrazol and A-rest did not have any effect. All of the treatments except A-rest suppressed the growth of `Better Boy' tomato and `Black Beauty' eggplant.

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Paul A. Thomas and Joyce G. Latimer

Perennial growers experience marketing difficulty when the stem length, or height of their perennial stock is excessive. Both wholesale and retail outlets desire to keep height to a minimum, while still promoting the production of flowers. The objective of this study was to screen containerized, spring-planted perennials for response to the growth retardants Sumagic, Bonzi, and B-Nine. Each perennial variety used was treated with B-Nine (Daminozide at 5000 ppm Bonzi (paclobutrazol) at 240 ppm, and Sumagic (uniconizole-P) at the following rates: 0, 40, 80, 120, and 160 ppm.Pre-cooled plugs of cultivars were selected from the genera Achillea, Coreopsis, Echinaceae, Digitalis, Gaillardia, Phlox, Rudbeckia, Alcea, Veronica, and Monarda. A randomized complete block design was implemented. Eight of the nine cultivars were responsive to Sumagic, with a 12% to 79% range of reduction in height. Seven cultivars were responsive to Bonzi with a 20% to 61% range of reduction. Only one cultivar was responsive to B-Nine, requiring two applications of 5000 ppm, to yield a 22% reduction in height at 4WAT. Based upon growers' desire for up to 50% height reduction, a 30% height reduction assessment point was established as a minimum rate for production, and a 50% to 60% reduction was established as the maximum landscape rate (based upon in-landscape persistence).