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Joyce G. Latimer and Ronald D. Oetting

Four-week-old salvia (Salvia splendens F. Sellow `Red Pillar') seedlings were treated with 0 or 50 ppm paclobutrazol, followed 5 h later by 0, 1, 2, or 4 times (0×, 1×, 2×, or 4×, respectively) the recommended label rate of bendiocarb (0.6 g a.i./liter), a carbamate insecticide. Seven days after treatment (DAT), phytotoxicity ratings increased with bendiocarb rate on all plants, but 50 ppm paclobutrazol reduced damage at 1× and 4× bendiocarb. Paclobutrazol also improved plant recovery from phytotoxicity damage at 21 DAT. Bendiocarb decreased the height of plants not treated with paclobutrazol at 7, 14, and 21 DAT. Plants treated with 40 ppm paclobutrazol had lower maximum phytotoxicity damage at 14 DAT, and even better recovery at 21 DAT than plants treated with 20 or 60 ppm paclobutrazol. Plants treated with paclobutrazol 4 days before applying bendiocarb had lower maximum phytotoxicity ratings relative to controls than plants treated 8 days before, the same day as, or 4 days after bendiocarb application. Chemical names used: β- [(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1 H- 1,2,4-triazole-1-ethanol (paclobutrazol); 2,2-dimethyl,1,3-benzodioxol-4-yl-methylcarbamate (bendiocarb).

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Xiao-Juan Wei, Jinlin Ma, Kai-Xiang Li, Xiao-Jing Liang, and Haiying Liang

minimizing the undesirable effects. Paclobutrazol is a triazole-type cytochrome P 450 inhibitor used extensively in horticulture as a plant growth retardant and fungicide. Its dual biological functions are because of the facts that PBZ possesses several

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Shravan Dasoju, Michael R. Evans, and Brian E. Whipker

Paclobutrazol drenches were applied at 0, 2, 4, 8, 16, or 32 mg a.i./pot to potted sunflowers (Helianthus annuus L. `Pacino') to determine its effect on growth. Plant height was shorter as paclobutrazol dose increased up to 16 mg; however, additional increases in dose had little effect on height. Severe height retardation of `Pacino' plants was evident at 16 and 32 mg. Plants treated with 2 mg of paclobutrazol were 17% and 25% smaller in diameter than untreated plants in Expts. 1 and 2, respectively. Plant diameter was smaller as paclobutrazol dose increased up to 16 mg, with additional increases in dose having little effect on plant diameter in Expt. 2. Plants treated with 16 or 32 mg of paclobutrazol exhibited phytotoxicity symptoms including crinkled leaves and stunted growth, and smaller and greener leaves. Sunflower plant growth was greater in the summer (Expt. 1) than in winter (Expt. 2). In the summer higher doses of paclobutrazol will be required than in winter for growth control. Marketable sized plants grown in 15- to 16.5-cm-diameter pots were produced with doses of paclobutrazol at 2 and 4 mg in both seasons, and doses up to 8 mg can also be used in summer for growth control.

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Xiao-Juan Wei, Jinlin Ma, Kun Wang, Xiao-Jing Liang, Jin-Xuan Lan, Yue-Juan Li, Kai-Xiang Li, and Haiying Liang

garden bags. PBZ (CAS no. 76738-62-0) was purchased from Anyang Quanfeng Biological Technology Co. Ltd. (He Nan Province, China) and contained 95% active components. Fig. 1. C. chrysantha seedlings and their paclobutrazol (PBZ)-induced reproductive buds

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Kristin L. Getter

probability values for plant growth index defined as [(plant height + plant width 1 + plant width 2)/3] shown by species and week number, modeled against average daily temperature (ADT) [16, 22, or 28 °C (60.8, 71.6, or 82.4 °F)] and paclobutrazol (PBZ) spray

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Patrick E. McCullough, Haibo Liu, Lambert B. McCarty, and Ted Whitwell

Research was conducted in two studies at the Clemson University Greenhouse Complex, Clemson, S.C., with the objective of evaluating `TifEagle' bermudagrass (Cynodon dactylon × C. transvaalensis) response to paclobutrazol. TifEagle bermudagrass plugs were placed in 40 cm polyvinylchloride containers, with 20.3-cm-diameters and built to U.S. Golf Association specifications with 85 sand: 15 peatmoss (by volume) rootzone mix. Paclobutrazol was applied to separate containers at 0, 0.14, 0.28, and 0.42 kg·ha-1 (a.i.) per 6 weeks. Minor phytotoxicity occurred with 0.14 kg·ha-1 applications, but turf quality was unaffected. Severe bermudagrass phytotoxicity occurred from paclobutrazol at 0.28 and 0.42 kg·ha-1. Total clipping yield from 12 sampling dates was reduced 65%, 84%, and 92% from 0.14, 0.28, and 0.42 kg·ha-1, respectively. Root mass after 12 weeks was reduced 28%, 45%, and 61% for turf treated 0.14, 0.28, and 0.42 kg·ha-1, respectively. Paclobutrazol reduced root length 13%, 19%, and 19% by 0.14, 0.28, and 0.42 kg·ha-1, respectively. Turf discoloration and negative rooting responses advocate caution when using paclobutrazol on `TifEagle' bermudagrass. Chemical names used: (+/-)-(R*,R*)-ß-[(4-chlorophenyl) methyl]-alpha-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol).

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James E. Barrett, Carolyn A. Bartuska, and Terril A. Nell

Paclobutrazol drench treatments were evaluated for efficacy on Caladium ×hortulanum (Birdsey) cultivars Aaron, White Christmas, and Carolyn Wharton. Drenches at 2.0 mg/pot did not reduce height of `Aaron' and `White Christmas' plants when applied 1 week after planting, but 2.0 mg applied at 3 weeks after planting did result in shorter plants. The difference for time of application may be due to the amount of roots present to take up paclobutrazol when applied. In two factorial experiments, there were no interactions between cultivar and time of application or amount of chemical. Paclobutrazol at 0.5 mg/pot resulted in plants that were shorter than the controls. Higher amounts of paclobutrazol provided additional reductions in height, but there was variation between the experiments for degree of effect with amounts >1 mg. Generally, commercially acceptable height control was provided by paclobutrazol drench treatments at 0.5 and 1.0 mg/pot applied 3 weeks after planting. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-pentan-3-ol (paclobutrazol).

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Patrick E. McCullough, Haibo Liu, and Lambert B. McCarty

Plant growth regulators are applied to inhibit uneven shoot growth of putting green turf but research is limited on responses of dwarf-type bermudagrass cultivars to growth inhibition. Experiments were conducted at the Clemson University Greenhouse Complex with `Champion' and `TifEagle' bermudagrass grown in polyvinylchloride containers with 40 cm depths and 177 cm2 areas built to United States Golf Association specification. Flurprimidol was applied at 0.14, 0.28, and 0.48 kg·ha–1 a.i. and paclobutrazol at 0.14 kg·ha–1 a.i. on separate containers. Flurprimidol at 0.28 and 0.42 kg·ha-1 caused 17% and 31% reduction in turf color 5 weeks after treatment (WAT), respectively. `Champion' exhibited unacceptable turf injury (>30%) 2 WAT from paclobutrazol and all flurprimidol rates. `TifEagle' had unacceptable turf injury from flurprimidol at 0.42 kg·ha–1 2 WAT, 0.28 kg·ha–1 3 WAT, and 0.14 kg·ha–1 4 WAT that did not recover. Moderate injury (16% to 30%) was observed from paclobutrazol on `TifEagle' but ratings were acceptable. After 6 weeks, flurprimidol at 0.14, 0.28, and 0.42 kg·ha–1 reduced bermudagrass green shoot density (GSD) per square centimeter by 20%, 40%, and 40%, respectively, while paclobutrazol reduced GSD 12%. `TifEagle' total clipping yield was reduced 60%, 76%, and 86% from flurprimidol at 0.14, 0.28, and 0.42 kg·ha–1, respectively, and 37% from paclobutrazol. `Champion' total clipping yield was reduced 82%, 90%, and 90% from flurprimidol at 0.14, 0.28, and 0.42 kg·ha–1, respectively, and 58% from paclobutrazol. After 6 weeks, flurprimidol reduced `Champion' total root mass by 44% over all three rates. `Champion' treated with paclobutrazol had similar total root mass to the untreated. `TifEagle' treated with all PGRs had similar rooting to the untreated. Overall, flurprimidol will likely not be suitable for dwarf bermudagrass maintenance at these rates; however paclobutrazol may have potential at ≤0.14 kg·ha–1. Chemical names used: Flurprimidol {α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl] 5-pyrimidine-methanol}; Paclobutrazol, (+/-)–(R*,R*)-β-[(4-chlorophenyl) methyl]-α-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol.

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Ali M. El-Khoreiby, C.R. Unrath, and L.J. Lehman

A single foliar spray of 250 mg paclobutrazol/liter was applied to 7-year-old `Oregon Spur Delicious' (OSD) or `Smoothee Golden Delicious' (SGD) apple trees (Malus domestica Borkh.) at 12 growth stages between tight cluster and petal fall plus 28 days. A linear increase in fruit length and length: diameter ratio and a linear decrease in percent soluble solids content were observed on OSD as sprays were applied later in the season. Russet formation on SGD was excessive if treatment was made between early bloom and petal fall. For both cultivars, best control of shoot growth and minimal change in fruit characteristics occurred when paclobutrazol was applied after bloom. Chemical name used: β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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Richard H. Zimmerman and George L. Steffens

Paclobutrazol was provided by ICI Americas. uniconazole by Chevron Chemical Co., and daminozide and ethephon by Uniroyal. We thank Larry Douglass for advice and useful discussion\ on cxperimental design and statistical analysis and Charles Mischke