You are looking at 1 - 8 of 8 items for
- Author or Editor: T. Whitwell x
This research focused on the potential use of common cattails (Typha latifolia) for removing metalaxyl and simazine residues from contaminated water. Specifically, it established toxicity thresholds to the herbicide simazine and characterized the uptake and distribution of simazine and metalaxyl by the plants. Simazine tolerance levels were determined by exposing plants to a series of six concentrations (0 to 3.0 mg/L) in aqueous nutrient media for 7 days. Metalaxyl toxicity was not evaluated because other studies indicated it was relatively non-toxic to plants. Toxicity endpoints measured included fresh mass production after 7 days exposure and 7 days post-exposure. Pesticide uptake and distribution were determined by growing plants in nutrient media amended with C-14-ring-labeled metalaxyl (0.909 mg/L) or simazine (0.242 mg/L) for 1, 3, 5, or 7 days. Plants were dissected and tissues were combusted and analyzed by liquid scintillation counting. Cattail fresh mass production was reduced 84% and 117% at 1.0 and 3.0 mg/L simazine, respectively, after 7 days of exposure. Metalaxyl and simazine activity in solution was reduced 34% and 65%, respectively, after 7 days. By day 7, activity from both pesticides was detected predominantly in the leaves. Uptake of each pesticide was correlated with water uptake throughout the 7 days. These results suggest that the common cattail may be a good candidate for incorporation into a phytoremediation scheme for metalaxyl and simazine.
Atrazine, simazine, and metalaxyl residues are often present in sprayer rinsates and in runoff water following application of the formulated products. As an initial step in the development of a constructed wetland for the phytoremediation of these pesticides in water, several plant species were evaluated for their tolerances to each. Plant species were chosen based on their aesthetics, tolerance to wetland conditions, and their potential to produce much vegetative growth. Species included: Acorus gramenius, Canna hybrida `King Humbert', Myriophyllum aquaticum, and Pontederia cordata. Plants were exposed to various concentrations of each pesticide dissolved in 10% Hoagland's nutrient media for 7 days. Tests were conducted under metal halide lamps with a light intensity of 400 μmol/m2 per s and a photoperiod of 16 h light: 8 h dark. Test endpoints measured included 7-day fresh mass production and chlorophyll fluorescence. A completely randomized statistical design with four replications of each concentration was utilized for each plant species. These tests indicate that all plant species were susceptible to atrazine and simazine in the 0.1 to 1 μg/ml range. Effected plants displayed concentration-dependent degrees of chlorosis and necrosis. Plants were more tolerant to metalaxyl concentrations in water. However, leaf chlorosis and necrosis did occur at concentrations greater than 25 μg/ml. Future research will quantify the uptake and mineralization potential for these plants and pesticides.
Ten crops were evaluated for potential use as field bioassay species for cinmethylin and chlorimuron application rates in two soil types. Cinmethylin injured sweet corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] at concentrations as low as 0.28 kg·ha-1 on either soil type, while broadleaf crops were tolerant. Chlorimuron injured sweet corn, grain sorghum, radish (Raphanus sativus L.), cucumber (Cucumis sativus L.), and watermelon [Citrullis lanatus (Thunb.) Mansf.] at rates ≥ 2.5 g·ha-1, and squash (Cucurbita pepo L.) at rates ≥ 5.0 g·ha-1 on a Dothan sand. In a Congaree silt loam, chlorimuron injured cucumber at rates ≥ 5.0 g·ha-1, sweet corn, watermelon, and squash at rates ≥ 10 g·ha-1, and grain sorghum, radish, and cotton (Gossypium hirsutum L.) at rates ≥ 20 g·ha-1. Soybean and snapbean (Phaseolus vulgaris L.) were tolerant to chlorimuron in both soil types. Cinmethylin activity was not altered by soil type, but with chlorimuron greater crop injury was observed in the Dothan sand than in the Congaree silt loam. Sweet corn and grain sorghum were the most sensitive indicator species to cinmethylin and cucumber was the most sensitive to chlorimuron in both soils. Plant emergence and population alone are not valid indicators for crop tolerance to herbicides. Quantitative measurements such as shoot dry weight were more indicative of crop susceptibility to chlorimuron than plant populations. Chemical names used: exo -1-methyl-4-(1-methylethyl)-2 -[(2-methylphenyl) methoxy]-7-oxabicyclo[2.2.1]heptane (cinmethylin); 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino] carbonyl]amino] sulfonyl]benzoic acid (chlorimuron).
In 1993, Carolina Nurseries and the Dept. of Horticulture at Clemson Univ. entered into a partnership for a research and development program to solve short- and long-term production problems in the ornamental nursery industry. Carolina Nurseries, located near Charleston, S.C., is a 110-ha commercial container-grown landscape plant nursery that sells >12 million units yearly. Research is conducted on site in a specially designed area that provides nursery conditions and control of other variables, including water and pesticide applications. An on-site graduate student works cooperatively with faculty on campus and manages the research area, collects data, maintains the projects using standard nursery practices, interacts with Carolina Nurseries personnel, and initiates needed studies. Over the past 6 years, research diversity increased with cooperative efforts from faculty in the Depts. of Entomology, Pathology, and Agricultural Engineering. In addition, cooperative studies with faculty members with Univ. of Georgia, Michigan State Univ., and North Carolina State Univ. have been completed. Research results were presented to the nursery industry at research update meetings at the research area site. Approximately 200 attendees from commercial nurseries and horticulture-related companies in surrounding states attended the 1998 research update. Surveys collected at research updates are helpful in tailoring research to the specific needs of the nursery industry, and are the basis for some of the current research projects. Research results are also in published in the Southern Nursery Association Research Proceedings, Journal of Environmental Horticulture, and The South Carolina Nurseryman Newsletter.
Absorption, translocation, and metabolism of foliar-applied 14C-labeled sethoxydim (14C-sethoxydim) in sethoxydim-tolerant centipedegrass [Eremochloa ophiuroides (Munro) Hack.] and sethoxydim-sensitive goosegrass [Eleusine indica (L.) Gaertn.] were determined. The distribution of 14C in treated leaves indicated that similar amounts (≈ 3%) were found in the epicuticular wax fraction (chloroform wash) of both species after 6 hours. After 2 hours, 16% of the applied 14C-sethoxydim was absorbed in the treated leaf by centipedegrass, but only 2% was absorbed by goosegrass. After 2 hours, centipedegrass also readily translocated greater amounts of 14C than goosegrass (4.3% vs. 0.4%). Six hours after treatment, however, no differences were found in amounts absorbed by the treated leaf and translocated to apical and basal leaves. Because sethoxydim-tolerant centipedegrass absorbed and translocated similar amounts of 14C compared to the sethoxydim-sensitive goosegrass, these two mechanisms do not appear to be a means of tolerance. The major difference found between the two species was in the metabolism of sethoxydim. After 6 hours, 81% to 98% of the 14C in goosegrass extracts remained as 14C-sethoxydim. In contrast, only 1% of the 14C found in apical leaves, basal leaves, and roots of centipedegrass was identified as 14C-sethoxydim. These data indicated that differences in tolerance to sethoxydim between these two species were based on metabolism. Chemical name used: 2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2 -cyclohexen-1-one (sethoxydim).
Oryzalin, simazine, and metolachlor alone and in combination were evaluated for weed control in field-grown Korean boxwood (Buxus microphylla Siebold & Zucc. ‘Koreana’) and Photinia (Photinia × fraseri) at Belle Mina, Ala., over a 3-year production period. Treatments were applied twice during each growing season. Greatest control of the annual grass and broadleaf weed species was with oryzalin tank-mixed simazine at rates of either 2.2 + 0.8 or 3.4 + 1.1 kg a.i. per ha−1, respectively. These treatments were not injurious to either species and consistently resulted in the highest growth indices. No injury was detected when additional liners of boxwood were planted in the treated plots at the termination of the experiment. Chemical names used: 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin); 6-chloro-N,N’-diethyl-1,3,5-triazine-2,4-diamine (simazine); and 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor).
Field experiments were conducted to evaluate response of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) and ‘Tifgreen II bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] to six postemergence herbicides. Fluazifop and sethoxydim were applied at 0.1, 0.2, and 0.3 kg ha−1. Fenoxaprop, haloxyfop, xylafop, and poppenate were evaluated at 0.07, 0.15, and 0.30 kg −1. Crop oil concentrate was added to each treatment at 2.4 liters·ha−1. Herbicides were applied in June 1985 to bentgrass, and in June and Aug. 1985 to bermudagrass. Bentgrass and bermudagrass had unacceptable color and density through 28 days after treatment (DAT) with all herbicides. Both species showed tolerance 28 DAT to fenoxaprop at 0.07 and 0.15 kg ha−1, but turf density was reduced compared to the untreated check. Bermudagrass quality at 42 and 49 DAT was not different from the untreated check with low and medium rates of fenoxaprop. All other herbicides reduced bentgrass and bermudagrass quality to unacceptable levels. Chemical names used: (±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); (±)-2[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate (fenoxaprop); (±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxyl]phenoxy]propanoic acid (fluazifop); 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid (haloxyfop); methyl-3-hydroxy-4[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]-pentanoate (poppenate); 2-[1-(ethoxyi-mino)butyl]-5-]2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim); 2-[4-[(6-chloro-2-quinoxalinyl)oxy]phenoxyl]propanoic acid (xylafop).
The phytotoxicity of single and sequential treatments of sethoxydim and fluazifop at 0.10, 0.20, and 0.30 kg·ha−1; haloxyfop, xylafop, fenoxaprop, and SC-1084 at 0.07, 0.15, and 0.30 kg·ha−1, on centipedegrass [Eremochloa ophiuroides (Munro.) Hack.] was determined. Turf color generally was unaffected by sethoxydim application except for a slight discoloration at 14 days after treatment (DAT) with the high rate. Recovery was evident from all rates of sethoxydim by 28 DAT. Turf density was similar to untreated control at 42 DAT. Single applications of fenoxaprop and SC 1084 at 0.07 kg·ha−1 initially caused severe discoloration; however, recovery was evident by 42 DAT. Density also was unaffected at this time. Unacceptable turf color and density were observed with single and sequential applications of fluazifop, haloxyfop, xylafop, and with sequential application of SC 1084 and fenoxaprop. Chemical names used: (2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-l-one (sethoxydim); (±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxyl]phenoxy]propanoic acid (fluazifop); 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]-phenoxyl]propanoic acid (haloxyfop); (2-[4-[(6-chloro-2-quinoxalinyl)-oxy]phenoxyl]propanoic acid (xylafop); (±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid (fenoxaprop); and methyl-3-hydroxy-4-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]-pentanoate (SC-1084).