Organic production systems rely heavily on cultural and mechanical weed control, with minimal dependence on herbicides that are approved for use in certified organic crops. Herbicides allowed for use in certified organic production systems are
W. Carroll Johnson III and Jerry W. Davis
John Wilhoit and Timothy Coolong
, 2005 ; Ngouajio and McGiffen, 2004 ). Currently, polyethylene (plastic) film-mulches are the primary mulch used in vegetable production for in-row weed control; however, weed control between rows can be a significant challenge for some producers. Weeds
S. Christopher Marble, Shawn T. Steed, Debalina Saha, and Yuvraj Khamare
Weed management in container plant production is challenging, primarily due to limited postemergence herbicide options and the consequential need for supplemental hand weeding ( Case et al., 2005 ). Currently, weed control in container nurseries is
Eva García-Méndez, David García-Sinovas, Maximo Becerril, Antońeta De Cal, Paloma Melgarejo, Anselmo Martínez-Treceño, Steven A. Fennimore, Carmen Soria, Juan J. Medina, and Jóse M. López-Aranda
must control weeds in strawberry nurseries because strawberry runner plant yields are sensitive to weed competition and because weeds can host many diseases ( Wilhelm and Paulus, 1980 ). Most weeds that infest Spanish strawberry nurseries are annual
Robert E. Uhlig, George Bird, Robert J. Richardson, and Bernard H. Zandstra
ornamental production. The objective of this study was to evaluate crop safety and weed control with pre-transplant applications of these fumigants on seven ornamental species. Materials and methods The experiment was conducted at a commercial nursery in
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.
Charles L. Webber and James W. Shrefler
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.
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.
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.
Robert J. Richardson and Bernard H. Zandstra
length of rotation and sensitivity of some species (especially young transplants) to weed competition, adequate weed control continues to be an important issue facing the industry. Chemical weed control provides numerous benefits over no weed control for