Nursery growers estimate that they spend $500 to $4000/acre ($1235 to $9880/ha) of containers for manual removal of weeds, depending upon weed species being removed. Economic losses due to weed infestations have been estimated at about $7000/acre ($17,290/ha). Herbicide treated bark nuggets were found extremely effective for weed control in studies during 1998, regardless of whether oxyfluorfen, oryzalin, or isoxaben were applied to the bark. A study conducted in 2000 compared 24 treatments of novel nonchemical alternatives, conventional chemical practices and herbicide treated barks. Four of the best treatments were herbicide treated douglas fir bark, specifically, small [<1 inch (2.5 cm) length] douglas fir nuggets treated with oryzalin at the 1× rate, large (>1 inch length) douglas fir nuggets treated with oryzalin at the 0.5× rate, small douglas fir nuggets treated with oryzalin at the 0.5× rate and large douglas fir nuggets treated with flumioxazin at the 1× rate. The four bark treatments indicated above provided equivalent efficacy and phytotoxicity to Geodiscs. Penn Mulch and Wulpack provided poor weed control. Mori Weed Bag, a black polyethylene sleeve, and Enviro LIDs, a plastic lid provided less control than herbicide treated bark. Compared to the bark alone, herbicide treated bark provides a 1.8-fold increase in efficacy and a 2.8-fold extension in duration of efficacy. Compared to the herbicide alone, herbicide treated bark provides a 1.5-fold increase in efficacy and a 2.2-fold reduction in phytotoxicity. Of the innovative weed control products tested herbicide treated bark provided the most promising results. The data support that the bark nuggets are possibly acting as slow release carriers for the herbicides or reducing the leaching potential of the herbicides. Recent studies have indicated that the controlled release of herbicides using lignin as the matrix offers a promising alternative technology for weed control.
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.
A field study was conducted in 2002 and 2003 to evaluate various herbicides (ethafluralin & clomazone, halosulfuron, and ethafluralin & clomazone + halosulfuron) with or without a winter rye (Secale cereale L.) cover crop in no-tillage `Daytona' cucumber (Cucumis sativus L.) production. All herbicides were applied preplant prior to cucumber transplanting, and no injury or stunting to cucumber was observed with any of the treatments evaluated at any time during the two growing seasons. Winter rye provided a significant advantage for weed control compared to the no cover crop production system. The combination of ethafluralin & clomazone + halosulfuron provided the greatest control of smooth crabgrass [Digitaria ischaemum (Schreb. Ex Schweig) Schreb. Ex Muhl.] and redroot pigweed (Amaranthus retroflexus L.). Ethafluralin & clomazone provided little redroot pig-weed control, while halosulfuron alone provided no control of smooth crabgrass. Winter rye enhanced cucumber yields in 2002 (drought conditions), while in 2003 (sufficient moisture and cooler soil temperatures), winter rye tended to suppress yields. During drought conditions (2002), treatments with ethafluralin & clomazone and ethafluralin & clomazone + halosulfuron produced similar yields. However, in 2003, treatments with ethafluralin & clomazone + halosulfuron produced greater yields than treatments with ethafluralin & clomazone. Overall, the handweed treatment provided the greatest yields, while the non-treated and halosulfuron only treatment provided the lowest yields. Winter rye will provide some additional weed control in a no-tillage vegetable production system, but may also provide negative effects by suppressing crop yield depending on seasonal growing conditions.
Selective broadleaf weed control is a major economic issue facing commercial landscapers and homeowners alike. Minimal selective post-emergent weed research has been successful in controlling landscape weeds. The objectives of this experiment were to determine the efficacy of seven selective broadleaf herbicides [nicosulfuron (0.66 oz/acre), flumioxazin (8 oz/acre), penoxsulam (2.3 fl oz/acre), bensulfuron (1.66 oz/acre), glyphosate (1% by volume), sulfentrazone (8 fl oz/acre), trifloxysulfuron (0.56 oz/acre) and the control] and to determine the ornamental phytotoxicity on three groundcover species (Liriope muscari, Ophiopogon japonicus, and Trachelospermum asiaticum). A RCBD design was used with five blocks. Each block was split establishing either mulched or bare soil plots (nonmulched). The ground-covers were established three months before herbicide application. On 29 June 2005, four weed species were evenly seeded into the blocks with one hundred seeds each of Sesbania exaltata, Ipomea hederacea, Amaranthus retroflexus, and Euphorbia maculata. Herbicides were applied using a CO2 backpack type sprayer on 6 Sept. 2005. Plant and weed control data were taken to evaluate phytotoxicity and efficacy at 0, 1, 7, 14, and 28 DAT. On 27 Oct. 2005, weeds were harvested from each plot and dried for a minimum of 48 h and weighed. No significant differences in phytotoxicity were observed on either Liriope muscari or Trachelospermum asiaticum. However, there was a significant increase in phytotoxicity exhibited by the Ophiopogon japonicus treated with sulfentrazone compared to all of the other herbicides. Glyphosate demonstrated the best overall control of all broadleaf weeds except Sesbania, while trifloxysulfuron showed the best control of Sesbania. There were no significant differences in herbicide efficacy between the mulched and nonmulched plots. Further research is being done to measure the effects of herbicide efficacy and phytotoxicity in 2006.
Approximately 50% of the asparagus plantations (3000 ha) in the Caborca, Sonora, area is furrow-irrigated. Under these conditions it is common to observe growing weeds in the furrow section, which impede water flow and compete for resources with the asparagus plant, finally reducing spear production and quality. Hence, the objective of this study was to validate herbicides to achieve an efficient annual weed control in the asparagus plantations. The validation plot was established in May 1998 on a commercial asparagus plantation that was highly infested mostly with annual grasses (Echinochloa colonum and E. crusgalli), and Amaranthus spp. and Portulaca oleracea as a secondary weeds. The herbicides and rates tested were: Prometrine (2 L·ha-1), Norflurazon (4 kg), Metribuzin (0.5 kg), Linuron (2 kg), and the control plot (no herbicide application). All the tested products showed significant weed control percentages compared with the control plot. Norflurazon, however, was clearly superior to the other herbicides, exhibiting a 100% control for a period of almost 18 weeks. Metribuzin had a 85% control for 12 weeks. Linuron and Prometrine exhibited a 68% and 47% control, respectively, for up to 12 weeks. Plant toxicity symptoms on the asparagus plant were not observed with any of the tested herbicides.
Oxyfluorfen was evaluated for weed control in sweet potatoes. In 1989, applications were made overtop transplants immediately after transplanting. The 1990 applications were made just prior to transplanting. Oxyfluorfen applied post-transplant at 0.38 lb ai/A and greater rates caused a significant reduction in crop vigor. A 1.0 lb ai/A rate of oxyfluorfen reduced crop vigor when applied pretransplant. All rates of oxyfluorfen controlled Brachiaria platyphylla, Digitaria sanguinalis, Cyperus iria, and Sesbania exaltata. Oxyfluorfen rates of 0.5 lb ai/A and greater were needed to consistently control Sida spinosa and Echinochloa crus-galli. Mollugo verticillata was controlled at all rates in 1989 but not controlled at all in 1990. Yields of all grades of sweet potato roots from plots treated with oxyfluorfen were not different from yields from plots treated with currently labeled herbicides. However, in 1989 yields from all oxyfluorfen-treated plots were lower than yields from the hoed check. In 1990, plots treated with oxyfluorfen at 0.25 or 0.38 lb ai/A had lower yields of No. 1 grade roots than the hoed check.
period is marked by an increase in weed populations when the transition is managed by growers who are accustomed to using synthetic herbicides to control weeds ( Martini et al., 2004 ). Few organically acceptable herbicides have been shown to be
Tolerance of transplanted black-eyed Susan (Rudbeckia hirta var. pulcherrima Farw.), lanceleaf coreopsis (Coreopsis lanceolata L.), shasta daisy (Chrysanthemum × superbum Bergmans ex. J. Ingram), purple coneflower [Echinacea purpurea (L.) Moench.], and blanket flower (Gaillardia aristata Pursh) to preemergence herbicides was evaluated in container trials. Herbicides were applied at the maximum use rate and twice the maximum use rate. Dithiopyr, pendimethalin, and prodiamine provided excellent control of spotted. spurge (Euphorbia maculata L.) and yellow woodsorrel (Oxalis stricta L.) with little injury to the five herbaceous perennials. DCPA, oxadiazon, and metolachlor were tolerated by all treated species, but these chemicals provided lower control of one or both weed species. Oryzalin, isoxaben + trifluralin, and napropamide caused unacceptable injury and shoot fresh-weight reductions in some of the perennials at one or both application rates. Chemical names used: dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate (DCPA); S,S-dimethyl 2-(difluoromethyl) -4-(2 -methylpropyl)-6-trifluoromethyl-3,5-pyridinedicarbothioate(dithiopyr);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);N,N-diethyl-2-(l-naphtha1enenyloxy) propanamide(napropamide);4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin);3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethy1)-l,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl) -3,4-dimethyl-2,6-dinitrobenzamine (pendimethalin); N,N-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzamine (trifluralin).
·ha −1 of CPL). Different letters, within each location, indicate significant differences at P = 0.05 by Duncan’s multiple range test. Soil treatment effects on weeds. After the phaseout of methyl bromide, weed control became one of the major issues in
Although CGM has been identified as an organic herbicide for weed control in turf and established vegetable plants, direct contact with vegetable seeds can decrease crop seedling development and plant survival by inhibiting root and shoot development. The objective of this research was to determine the impact of banded corn gluten meal applications on squash plant survival and yields. This factorial field study was conducted during Summer 2005 on 81-cm-wide raised beds at Lane, Okla., with two application configurations (banded and solid), two CGM formulations (powdered and granulated), two incorporation treatments (incorporated and nonincorporated), and three application rates (250, 500, and 750 g·m–2). The two CGM formulations at three application rates were uniformly applied in both banded and solid patterns on 19 Aug. The banded application created a 7.6-cm wide CGM-free planting zone in the middle of the raised bed. The CGM applications were then either incorporated into the top 2.5 to 5.0 cm of the soil surface with a rolling cultivator or left undisturbed on the soil surface. `Lemondrop' summer squash (Cucurbita pepo L.) was then direct-seeded into the center of the raised beds. When averaged across the other factors, there was no significant difference between powdered and granulated CGM formulations or incorporating and nonincorporating the CGM for either squash plant survival or yields. As the CGM application rates increased the plant survival and yields decreased. Banded application resulted in significantly greater crop safety (90% plant survival) and yields (445 cartons/ha) than the broadcast (solid) applications (45% plant survival and 314 cartons/ha). The research demonstrated the potential usefulness of CGM in direct-seeded squash production, if used in banded application configuration.