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James E. Klett, Laurel Potts, and David Staats

During the 1998 season, preemergent herbicides were applied to container-grown herbaceous perennials and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. The herbicides and rates were: Napropamide (Devrinol 10G), 0.72 and 1.44 kg a.i./ha; Oryzalin (Surflan 40AS), 0.36 and 0.72 kg a.i./ha; Oxadiazon (Ronstar 2G), 0.72 and 1.44 kg a.i./ha; Oxyfluorfen + Oryzalin (Rout 3G), 0.54 and 2.16 kg a.i./ha; Oxyfluorfen + Pendimethalin (Scott's OH II), 0.54 and 1.09 kg a.i./ha; and Trifluralin (Treflan 5G), 0.72 and 1.44 kg a.i./ha. Herbicides were applied to Phalaris arundinacea `Picta', Scabiosa caucasica, Sedum × `Autumn Joy', Pennisetum setaceum `Rubrum', Salvia argentea, Penstemon × mexicali `Red Rocks', Osteospermum barberiae v. compactum `Purple Mountain', and Gazania linearis `Colorado Gold'. Phytotoxicity symptoms (visual defects) were apparent with Napropamide on Phalaris (at both rates) but recovered by the end of season. All herbicides provided good weed control.

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Efren C. Celaya and Brenda S. Smith

A field experiment was conducted on broccoli (Taki Marathon variety) at California Polytechnic State University, San Luis Obispo to evaluate three rates of AN-20 for weed control and crop phytotoxicity. The rates were: low-40 gal./A, standard-60 gal./A, high-80 gal./A, and untreated control. Each treatment was applied to the base of the broccoli plant to avoid crop injury. Each treatment had four replications. Data collected included hoe time/plot and percent visual control. Broccoli was not injured at any rate of AN-20. It was noticed that the older weeds, greater than five-leaf stage, managed to pull through, so size of weed is crucial. On a cost-per-acre basis, the money saved on the high rate is half that of the low rate and one third that of the control. Weed control was not adequately controlled at the standard and low rates. An economic analysis was conducted, and it was found there was a savings as less labor was required to hoe the field when AN-20 had been applied.

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David Staats, James Klett, Teri Howlett, and Matt Rogoyski

During the 2005 season, three preemergence herbicides were applied to four container-grown herbaceous perennials and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicides and application rates were: 1) Pendimethalin (Pendulum 2G) 2.24, 4.48, and 8.96 kg/ha; 2) Trifluralin and Isoxaben (Snapshot 2.5 TG) 2.8, 5.6, and 11.2 kg/ha; and 3) S-metolachlor (Pennant Magnum 7.6 EC) 2.8, 5.6, and 11.2 kg/ha. Herbicides were applied to Coral Bells (Heuchera sanguinea), Hopflower Oregano (Origanum libanoticum), CORONADO™ Hyssop (Agastache aurantiaca), and SPANISH PEAKS™ Foxglove (Digitalis thapsi). Treatments were applied twice with 30 days between applications. Plants were evaluated for phytotoxicity after 1, 2, and 4 weeks after applying herbicide treatments. No phytotoxicity symptoms were apparent on any of the plants treated with Pendulum, and plant size (dry mass) was not affected. Snapshot resulted in visual phytotoxicity with Digitalis and Heuchera at the higher rates and also resulted in smaller plants. Pennant Magnum caused phytotoxicity at all rates in all plants and resulted in significantly smaller plants than the control. Weed control was very good with all herbicides, but did not control every weed.

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Brian A. Kahn, Raymond Joe Schatzer, and Wendy A. Nelson

The herbicides trifluralin, metolachlor, and paraquat were compared for efficacy of weed control in cowpea with and without cultivation as a supplemental strategy for two years. Herbicides also were compared against a no-herbicide control (with and without cultivation). Cultivation had no significant effect on seed yield, biological yield, or harvest index of cowpea. Paraquat, used in a “stale seedbed” system, was ineffective for weed control and did not change cowpea yield from that of the no-herbicide control. Trifluralin and metolachlor more then tripled cowpea seed yield compared to that of the no-herbicide control in 1988, when potential weed pressure was 886 g m-2 (dry wt.). Trifluralin and metolachlor did not significantly increase cowpea seed yield compared to that of the no-herbicide control in 1989, when potential weed pressure was 319 g m-2 (dry wt.). However, in 1989, these two herbicides each still increased net farm income by $206 per hectare compared to the income obtained without an herbicide.

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Bonnie L. Appleton and Jeffrey F. Derr

Disks of several geotextiles, paper, fiberglass, and black polyethylene were compared with the herbicides oxyfluorfen plus pendimethalin, oxadiazon, and oryzalin plus benefin for suppression of weed growth around container-grown Southwestern white pine (Pinus strobiformis Engelm.), Chinese pistache (Pistacia chinensis Bunge.), and `Fashion' azalea [Rhododendron indicum (L.) Sweet × `Fashion']. The greatest weed control was obtained with a combination geotextile-preemergence herbicide (trifluralin) disk, indicating a possible new method of container weed control. Several of the barrier materials, including heavy wrapping and compressed peatmoss papers, black polyethylene, and one spunbonded geotextile, were inferior due to degradation or to weeds growing around the disk edges or center hole. No difference in crop growth was noted among the treatments. Chemical names used: 2-chloro-1- (3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (oxyfluorfen); N-(1-ethylpropyl)-3,4 -dimethyl-2,6-dinitrobenzenamine (pendimethalin); 3-[2,4-dichloro-5 -(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); 4-(dipropylamino) -3,5 -dinitrobenzenesulfonamide (oryzalin); N-butyl-N-ethyl-2,6 -dinitro-4-(trifluoromethyl) benzenamine (benefin); 2,6-dinitro-N,N-dipropyl-4-(ttifluoromethyl)benzenamine (trifluralin).

Open access

Paulus P. Shelby Jr., David L. Coffey, G. Neil Rhodes Jr., and Larry S. Jeffery

Abstract

Field studies were conducted in 1983 and 1984 to evaluate the feasibility of growing fresh-market tomatoes (Lycopersicon esculentum Mill. ‘Floradade’) in no-tillage or conventional tillage systems and to evaluate the efficacy of postemergence herbicides under both tillage systems. In 1983, marketable fruit yields in no-tillage were nearly twice those from conventional tillage. In 1984, there were no statistical differences in marketable yields among herbicide treatments or between tillage systems. Yields were higher in 1984 than in 1983, largely due to more favorable growing conditions. In both years, metribuzin provided good broadleaf weed control. In 1983, annual grasses were better controlled in no-tillage with a sequential metribuzin application for fluazifop following metribuzin than with a single metribuzin application. Marketable yields were highest in plots where annual grasses were adequately controlled. Sequential metribuzin applications provided good broadleaf weed control and postemergence grass herbicides each provided excellent annual grass control in 1984. Chemical names used: (±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid (fluazifop); 4-amino-6-(1,1-diemthylethyl)-3-(methyIthio)-1,2,4-triazin-5(4H)-one (metribuzin).

Open access

R. H. Stamps and D. D. Mathur

Abstract

Four herbicides, alone and/or in combination, were evaluated for weed control in beds of leatherleaf fern [Rumohra adiantiformis (G. Forst) Ching]. Fair winter weed, predominantly chick weed [Stellaria media (L.) Cyr.], control was obtained with simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] at 2 kg active ingredient (a.i.)/ha, simazine + metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] at 1.1 + 2.2 kg a.i./ha and oxadiazon [2-terf-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] + simazine at 1.1 + 1.1 kg a.i./ha. Oxadiazon + simazine, oxadiazon + metolachlor at 1.1 + 2.2 kg a.i./ha, and simazine + metolachlor controlled spring weeds. All herbicide treatments gave fair weed control in summer. Except for simazine applied alone, none of the treatments injured leatherleaf fern visibly. Oxadiazon + metolachlor, oxadiazon + simazine, and simazine + metolachlor reduced winter weeding times. All combination treatments reduced spring weeding times, but none of the treatments reduced summer weeding times. No treatment reduced fern yield or affected average frond weights. Frond length and frond weight were positively correlated (r = 0.74).

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James W. Shrefler, Charles L. Webber III, and Otis L. Faulkenberry III

Producers of organic vegetables often report that weeds are a troublesome production problem. It has been documented that corn gluten meal (CGM), a by-product of the wet-milling process of corn, is phytotoxic. As a preemergence or preplant-incorporated herbicide, CGM inhibits root development, decreases shoot length, and reduces plant survival of weed or crop seedlings. The development of a mechanized application method for CGM and the ability to apply the material in a banded pattern would increase its potential use in organic vegetable production, especially in direct-seeded vegetables. Therefore, the objective of this research was to develop a mechanized method to uniformly apply CGM to the soil surface in either a broadcast or banded pattern. An applicator was assembled using various machinery components (fertilizer box, rotating agitator blades, 12-volt motor, and fan shaped gravity-fed row banding applicators). The equipment was evaluated for the application of two CGM formulations (powdered and granulated), three application rates (250, 500, and 750 g·m–2), and two application configurations (solid and banded). Field evaluations were conducted during Summer 2004 on 81-cm-wide raised beds at Lane, Okla. Differences between CGM formulations affected the flow rate within and between application configurations. The granulated formulation flowed at a faster rate, without clumping, compared to the powdered formulation. While the CGM in the banded configuration flowed faster than the solid application. It was determined that the CGM powder used with the solid application configuration was inconsistent, unreliable, and thus not feasible for use with this equipment without further modifications. These evaluations demonstrated the feasibility of using equipment, rather than manual applications, to apply CGM to raised beds for organic weed control purposes. Several design alterations may increase the efficiency and potential usefulness of this equipment. If research determines equivalent weed control efficacy between the two CGM formulations, the granulated formulation would be the preferred formulation for use in this equipment. This equipment would be useful for evaluating the benefits of banded applications of CGM for weed control efficacy and crop safety for direct seeded vegetables.

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James E. Klett and David Staats

Herbicides were applied to container grown landscape plants and evaluated on the basis of weed control, phytotoxicity, and effect on plant growth. Three preemergent herbicides were applied including: Oxadiazon (Ronstar) at 4.54 and 9.08 kg/ha, Oxyfluorfen + Oryzalin (Rout) at 3.41 and 6.81 kg/ha and Oryzalin (Surflan) at 2.27 and 4.54 kg/ha. There was also a weedy and non-weedy control. The plant species included: Syringa vulgaris (Common Lilac), Wisteria sinensis (Chinese Wisteria), Phlox paniculata (Garden Phlox) and Dahlia hybrid (Garden Dahlia). They were all grown in number one containers in a media of soil, spaghnum peat moss, and plaster sand (1:2:1 by volume). All herbicides tested controlled weeds effectively with no phytotoxicity except with Phlox paniculata. Oryzalin resulted in a phytotoxic effect on Phlox paniculata at both the 1x and 2x rates.

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Angela K. Tedesco, Gail R. Nonnecke, Nick E. Christians, John J. Obrycki, and Mark L. Gleason

Field plots of four production systems of `Tristar' dayneutral and `Earliglow' June-bearing strawberry (Fragaria ×ananassa Duch.), established in 1993, included conventional practices (CONV), integrated crop management practices (ICM), organic practices using granulated corn gluten meal, a natural weed control product, (ORG-CGM), and organic practices using a natural turkey manure product (ORG-TM). `Earliglow' total yield from CONV plots in 1994 was similar to ICM and ORG-CGM, but greater than ORG-TM. Average berry weight and marketable yield were greater in the CONV system than both organic systems. CONV, ICM, and ORG-CGM plots had more runners and daughter plants than ORG-TM. Plots with CONV herbicide treatments were similar to ICM and ORG-CGM for percentage weed cover 1 month after renovation. `Tristar' crown number, crown and root dry weights, yield, and berry number were reduced when plants were grown under straw mulch in ORG-CGM and ORG-TM compared to CONV and ICM plots with polyethylene mulch.