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Timothy L. Grey, Glenn R. Wehtje, Ben F. Hajek, Charles H. Gilliam, Gary J. Keever and Patrick Pace

Adsorption, mobility, and filtration ability of organic media toward metolachlor were evaluated in a series of laboratory experiments. Experimental variables included media type, metolachlor concentration, and equilibration time. Adsorption isotherms were determined by applying the log form of the Freundlich equation. Mobility was evaluated using glass columns filled with media, which were then surface spiked with metolachlor and then leached daily for 10 consecutive days. Peat, pine bark, combinations of these two media and a mixture of pine bark and sand adsorbed >90% of the 14C metolachlor. Freundlich sorption coefficients were 10.9, 18.2, 13.4, 14.2, and 11.0 for pine bark, peat, 5 pine bark: 1 peat, 3 pine bark: 1 peat, and 5 pine bark: 1 sand, respectively. In a timed exposure experiment using bark, minimum metolachlor adsorption (57%) was at 90 seconds and maximum adsorption (82%) required at least 1440 minutes. In column leaching studies, data for all media indicate that metolachlor is relatively immobile through these substrates. An initial pulse of metolachlor (<1.0 μg·liter-1) was detected with each medium up to the third wetting event with a subsequent decline (>0.5 μg·liter-1 for each medium) in the metolachlor recovered. Filtration efficiency of commercially formulated metolachlor from water passed through different lengths of pine bark filled filters was 0%, 17%, 20%, 22%, 23%, and 29% for filters 4, 20, 12, 8, 16, and 24 cm in length, respectively. These results support the contention that such filtration would be effective provided the residence time of water within the filter was sufficient for adsorption of the contaminant by the media to occur.

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Jeffrey F. Derr

The tolerance of transplanted lanceleaf coreopsis (Coreopsis lanceolata L.), ox-eye daisy (Chrysanthemum leucantheum L.), purple cone flower [Echinacea purpurea (L.) Moench.], and blanket flower (Gaillardia aristata Pursh) to metolachlor was determined in field trials. Metolachlor at 4.5 kg·ha-1 (maximum use rate) and 9.0 kg·ha-1 (twice the maximum use rate) did not reduce stand or flowering of any wildflower species after one or two applications, although plants developed transient visible injury. Combining metolachlor with the broadleaf herbicides simazine or isoxaben resulted in unacceptable injury and stand reduction, especially in ox-eye daisy. Metolachlor plus oxadiazon was less injurious to the wildflowers than metolachlor plus either simazine or isoxaben. Treatments containing metolachlor controlled yellow nutsedge (Cyperus esculentus L.) by at least 89% in both experiments. Treatments containing isoxaben controlled eclipta (Eclipta alba L.). 100% in both studies. Chemical names used: N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide (isoxaben); 2-chloro -N-(2-ethyl-6-methylphenyl) -N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 3-[2,4-di-chloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3 H) -one (oxadiazon); 6-chloro -N,N' -diethyl-1,3,5-triazine-2,4-diamine (simazine).

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Dennis C. Odero, Jose V. Fernandez and Nikol Havranek

L.) ( Legal Information Institute, 2010 ). Recently, S -metolachlor was registered for preemergence weed control in root and tuber vegetable crops Group 1B under Special Local Needs 24 (c) registration through the Third Party Registrations, Inc., a

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Wayne C. Porter

Studies were conducted to evaluate metolachlor for weed control and crop tolerance in sweet potatoes. Metolachlor was applied posttransplant at rates of 0.5, 1.0, or 2.0 lb/A. Tank-mix combinations of metolachlor + clomazone were also evaluated. Clomazone was the standard herbicide used for comparison. Metolachlor alone or in combination with clomazone did not cause any serious reduction in sweet potato plant vigor when applied posttransplant. Metolachlor provided excellent control of Brachiaria platyphylla, Cyperus iria, Cyperus esculentus, and Amaranthus hybridus. Tank-mixes with clomazone did not improve the weed control of metolachlor alone. Yields of No. 1 and marketable roots from metolachlor treated plots were equal to or greater than yields from plots treated with clomazone.

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Wayne C. Porter

Metolachlor herbicide is being evaluated for preemergent weed control in sweetpotatoes due to its ability to control yellow nutsedge (Cyprus esculentus) and rice flatsedge (C. iria). Registration of metolachlor has been delayed because of reports in North Carolina of injury to sweetpotato roots. This study was initiated to determine the response of sweetpotato cultivars to metolachlor rates. Metolachlor at 1.12, 2.24, and 3.36 kg·ha–1 was applied to `Beauregard', `Hernandez', `Jewel', and `Darby' sweetpotatoes after transplanting. All rates of metolachlor provided good control of sedges. No significant cultivar × metolachlor interactions were found in the yield of no. 1, canners, marketable, or percent no. 1 sweetpotatoes. In plots treated with metolachlor at 2.24 kg·ha–1, only `Beauregard' sweetpotatoes produced jumbo grade roots. No evidence of misshapen roots due to any herbicide rate was noted.

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Darren E. Robinson, Kristen McNaughton and Nader Soltani

pigweed ( Amaranthus retroflexus L.), common ragweed ( Ambrosia artemisiifolia L.), common lambsquarters ( Chenopodium album L.), and eastern black nightshade ( Solanum ptycanthum Dun.). Napropamide, trifluralin, chlorthal dimethyl, and s-metolachlor

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J.D. Gaynor, A.S. Hamill and D.C. MacTavish

Metolachlor was evaluated for annual grass and eastern black nightshade (Solarium ptycanthum Dun.) control in processing tomato (Lycopersicon esculentum Mill.). Metolachlor applied preplant incorporated provided excellent (> 88%) control of annual grasses and eastern black nightshade. The metolachlor, metribuzin plus trifluralin tank mix applied preplant and incorporated into the soil provided better annual grass and eastern black nightshade control than the metolachlor plus metribuzin tank mix in two of three years. Nonincorporated and posttransplant treatments of metolachlor provided good annual grass control but failed to control eastern black nightshade. Tomato yield in all herbicide treatments was similar to that from hand weeded controls. Metolachlor dissipated from the soil throughout the growing season so that at the time of harvest <10% of that applied was recovered. Metolachlor residues in the fruit were hydrolyzed to deacylated (CGA 37913) or hydrolyzed conjugated (CGA 49751) metolachlor metabolizes. Analyses of extracts from treated fruits were found to be less than the detection limit of 50 ppb in the whole fruit harvested from selected metolachlor treatments. Chemical names used: 2-chloro-N -(2-ethyl-6-methylphenyl)-N -(2-methoxy-1-methylethyl) acetamide (metolachlor); 2,6-dinitro-N,N -dipropyl-4-(trifluromethyl)benzenamine (trifluralin); 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-tlriazin-5(4H)-one (metribuzin); 2-(2-ethyl-6-methylphenyl)amino-1-propanol (CGA 37913); 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morphol. inone (CGA 49751).

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Jayesh B. Samtani, John B. Masiunas and James E. Appleby

[ Glycine max (L.) Merr.] planting or postemergence applications of glyphosate. Based on these observations, we theorized that leaf tatters was caused by drift from herbicide applications before or at corn planting. Atrazine, glyphosate, s-metolachlor

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Wheeler G. Foshee III, Collin W. Adcock, Glenn R. Wehtje, Charles H. Gilliam and Larry W. Wells

Effects of combining labeled rates of halosulfuron (Sandea) and s-metolachlor (Dual Magnum) were evaluated as a preemergence (PRE) application in a randomized complete block designed experiment at the Wiregrass Experiment Station in southeastern Alabama. Treatments were assigned in a factorial arrangement of four levels of halosulfuron (0.0, 0.009, 0.018, and 0.036 lbs. a.i./acre) and six levels of s-metolachlor (0.0, 0.25, 0.50, 0.75, 1.0, and 1.25 lbs. a.i/acre). The purpose of the study was to ascertain possible synergistic effects from combining these two herbicides to control nutsedge at a possible lower cost. Two repetitions were completed in 2005 with data pooled in analysis. Results found no interaction between the halosulfuron and the s-metolachlor and therefore no synergistic affects. Analysis of the main effects revealed that the highest labeled rate of either herbicide gave the highest percent control relative to the nontreated control. Soil activity of halosulfuron in controlling nutsedge has been shown to be less effective than foliar applications. Our own LD90 greenhouse studies confirmed this to be true. We examined four application techniques of halosulfuron (POST both soil and foliar, POST foliar only, POST soil only, and PRE soil only) to determine the LD90. Results revealed that halosulfuron had the lowest LD90 from the treatments with a foliar application. However, some soil activity was observed. Results from field studies indicated that PRE applications of halosulfuron must be at the highest labeled rate to provide effective control. S-metolachlor was equal to halosulfuron on percent control and is lower in cost on a per acre basis.

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Kassim Al-Khatib, Carl Libbey and Sorkel Kadir

Broadleaf weed control with trifluralin, oxyfluorfen, pendimethalin, clopyralid, pyridate, and metolachlor in cabbage (Brassica oleracea L.) grown for seed was evaluated. No single herbicide controlled broadleaf weeds adequately, with the exception of pendimethalin at 1.92 and 3.84 kg a.i./ha. However, combinations of trifluralin + oxyfluorfen, pendimethalin + clopyralid, and oxyfluorfen + pyridate effectively controlled weeds and did not reduce seed yields. Herbicides caused slight to moderate injury symptoms to cabbage plants, with the greatest injury caused by pendimethalin and the least by trifluralin and metolachlor. However, plants recovered from these symptoms and appeared normal at the bud stage. None of the herbicides applied alone or in combinations adversely affected cabbage population, height, or flowering date. Chemical names used: 3,6-dichloro-2-pyridinecarboxylic acid (clopyralid); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (oxyfluorfen); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin); O-(6-chloro-3-phenyl-4-pyridazin-yl)S-octylcarbonothioate (pyridate); 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine (trifluralin).