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is less commonly used in container nursery production but may be used as a nonchemical weed management option for sensitive plant species ( Case et al., 2005 ). Many different mulch materials have been evaluated for weed control in container plants

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Several approaches can be taken to minimize weed intrusion of wildflower plantings. To suppress existing weed seeds, the primary and most important cultural practice is proper seedbed preparation. Research has shown that short-term preemergent herbicides, multiple tillings, solarization, and fumigation can result in good weed control during the initial year of wildflower establishment. Other strategies include increased seeding rates, use of aggressive species, and selective herbicides.

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Producers and researchers are interested in pelargonic acid (nonanoic acid) as a broad-spectrum postemergence or burn-down herbicide. Pelargonic acid is a fatty acid naturally occurring in many plants and animals, and present in many foods we consume. The objective of this research was to determine the effect of pelargonic acid concentration, adjuvants, and application timing on weed control efficacy as a burn-down herbicide. Field research was conducted at Lane, Okla. (southeast Oklahoma), during the 2005 growing season. One month prior to spraying the weed control treatments, the land was cultivated to kill the existing weeds and provide a uniform seed bed for new weed growth. The factorial weed control treatments included three application concentrations of Scythe (57.0% pelargonic acid) applied at 3%, 6.5%, and 10%; three adjuvants (none, orange oil, and non-ionic surfactant); and two application dates. All herbicide treatments were applied with an application volume of 935 L/ha to seedling weeds. The experiment had a high weed density with multiple species of grass and broadleaf weeds. Weed control across species increased as the herbicide concentrations increased from 0% to 10%. At all concentrations applied, pelargonic acid produced greater weed control for a longer time period for the broadleaf weeds than the grass weeds. Visual damage to the weeds was often apparent within a few hours after application. There was a significant increase in weed control when applied to the younger weeds. In this research, pelargonic acid was effective in controlling both broadleaf and grass weeds as a burn-down herbicide, although crabgrass was tougher to control.

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Lack of effective weed control is the major limiting factor in strawberry production. With few herbicides labeled for use in this perennial crop, weeds are controlled using manual labor, cultivation, and one or two herbicide applications. However, these practices do not provide long-term, effective weed control, and weeds continue to be the number one reason why strawberry fields are removed from production due to a reduction in yield. The objective of this study was to evaluate weed control during strawberry plant establishment using woven woolen mats and spring-sown canola. The effects of these mulches on weed control and strawberry plant production were studied independently and in tandem. Weed and daughter plant counts were compared among treatments to test for differences. Wool mulch, both single- and two-ply, was an effective barrier to weeds within the strawberry rows. Planting canola between rows or broadcasting in combination with the wool mulch decreased the number of weeds when compared to other treatments. The four treatments that included wool had the highest number of rooted daughter plants when compared to all the other treatments except the weed-free plot. The canola treatments without wool mulch did not produce as many rooted daughter plants and were not statistically different from the weedy-check.

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Field studies were conducted at Absaraka, Carrington, and Oakes, N.D., in 2005 to evaluate early season broadleaf weed control and onion (Allium cepa L.) injury with herbicides applied preemergence to the crop. DCPA is a common preemergence herbicide used in onion. However, DCPA can be uneconomical in most high-weed situations, or the usage may be restricted due to possible groundwater contamination. Potential substitutes evaluated were bromoxynil, dimethenamid-P, and pendimethalin. Main broadleaf weeds were redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.). In general, all herbicides, except bromoxynil, provided acceptable broadleaf weed control 4 weeks after treatment. The highest herbicide rate provided greater weed control compared with the lowest rate for each herbicide. However, onion height was also reduced with the highest herbicide rate. In addition, the two highest rates of dimethenamid-P reduced the onion stand compared with the untreated. A postemergence application of bromoxynil + oxyfluorfen + pendimethalin to onion at the four- to five-leaf stage controlled the few broadleaf weeds that escaped the preemergence treatments and provided residual control of mid- and late-season germinating broadleaf weeds at two of the three locations. Intense germination of redroot pigweed during July at the Oakes location reduced onion yield with all treatments compared with the hand-weeded check. In contrast, total onion yields with all herbicide treatments except the high rate of dimethenamid-P were similar to the hand-weeded check at Absaraka and Carrington.

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Abstract

Seven herbicides, alone or in combinations, were tested for weed control on watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai cv. Charleston Gray, and cucumber, Cucumis sativus L. cv. Chipper, during 1967 to 1972. Preemergence applications of nitralin (4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline) controlled most weed species without seriously injuring either crop. The combination of bensulide (O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl) benzenesulfonamide) with either chloramben, methyl ester (methyl 3-amino-2,5-dichlorobenzoate) or naptalam (N-1-naphthylphthalamic acid) controlled a broader spectrum of weeds than any of the compounds applied singly.

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Abstract

The control of annual weeds in young prune orchards increased growth. The degree of foliar expressed phytotoxicity did not result in decreased tree growth. Simazine gave long lasting weed control and the most foliar symptoms on prunes, but superior tree growth. Simazine and dichlobenil produced more foliar symptoms than diphenamid, but less indication of growth reduction.

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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.

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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.

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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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