Cyclanilide Alterations In Growth Of Five Landscape Plant Species During Container Production Are Location Specific

Abstract

Abstract Five species of tropical and warm temperate shrubs, bush morning glory (Ipomoea carnea N. von Jacquin subsp. fistulosa (K. von Martinus ex J. Choisy) D. Austin), Indian hawthorn (Raphiolepis indica (L.) J. Lindley), tropical hibiscus (Hibiscus rosa-sinensis L. ‘Brilliantissima’), jatropha (Jatropha integerrima N. von Jacquin), and nandina (Nandina domestica C.P. Thunberg), were grown in 2.8-liter (#1) black plastic containers at two contrasting nursery locations and regimes. In College Station, TX, plants were grown in full sun under high fertility conditions, while in Dallas, TX, plants were grown under 40% light exclusion and a lower fertility level. Plants at each location were sprayed to runoff, either once or twice, with a distilled water only control, a Latron B-1956 spreader sticker surfactant at 0.063 mg/liter (0.063 ppm) in distilled water, or cyclanilide [1-(2,4-dichlorophenyaminocarbonyl)-cyclopropane carboxylic acid] at 56, 112, or 223 mg/liter (56, 112, or 223 ppm, respectively) with the Latron surfactant in a distilled water carrier. Half of the plants in all treatments received a single application, while the other half received a second application two to three weeks later. Although growth responses and release of dormancy varied among species and with cyclanilide concentration, plants of most species had greater release of lateral buds from a dormant or quiescent state under the high irradiance and fertility conditions in College Station, compared to the lower irradiance and fertility conditions in Dallas. However, phytotoxicity symptoms as evidenced by lower quality ratings were also more prevalent in College Station. Phytotoxicity was moderate to severe on nearly all jatropha and tropical hibiscus plants exposed to cyclanilide. Toxicity symptoms and significant growth reductions were present on several species at 112 or 223 mg/liter (112 or 223 ppm, respectively). A second application usually increased the effects on growth responses at all concentrations and often induced phytotoxicity symptoms at 56 mg/liter (56 ppm). The disparate responses between the two locations suggest the importance of local growing conditions on the potential efficacy and predictability of responses to cyclanilide applications.