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Emily E. Hoover, Frank Forcella, Neil Hansen, Steve Poppe, and Faye Propsom

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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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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W.L. Corley

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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Hannah M. Mathers

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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Harlene M. Hatterman-Valenti, Carrie E. Schumacher, Collin P. Auwarter, and Paul E. Hendrickson

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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S. Alan Walters*, Scott A. Nolte, Joseph L. Matthews, and Bryan G. Young

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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Christina Walsworth, Edward Bush, Ronald Strahan, and Ann Gray

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.

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Wayne C. Porter

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.

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Chuck Ingels and John Roncoroni

plants spread by rhizomes. Closer spacing of transplants is cost-prohibitive for larger plantings, and wider spacing exacerbates weed competition for 1 year or more. Weed control is essential in weedy sites for 1 year to reduce the weed seed bank

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Charles L. Webber III and James W. Shrefler

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.