Weed control ratings at 3 weeks after treatment (WAT) showed that knotweed (Polvgonum argyrocoleon) and yellow sweetclover (Melilotus officinalis) were not controlled by oxyfluorfen (Goal®), pyridate (Lentagran®), clopyralid (Stinger®), sulfentrazone (FMC), or carfentrazone (FMC). Carfentrazone at 0.50 lb AI/A gave good control ( >89 %) of London rocket (Sisvmbrium irio) and sowthistle (Sonchus oleraceus). A lower rate at 0.125 lb AI/A provided acceptable control (85 %). Carfentrazone at 0.50 lb AUA caused severe broccoli and cabbage injury and crop stand reduction. Sulfentrazone at 0.50 lb AI/A gave nearly acceptable control of knotweed, London rocket, and sowthistle. Cabbage was severely injured and broccoli appeared to be more tolerant and injury was marginally acceptable (15 %). Stinger and Goal gave nearly acceptable control of sowthistle. Goal at 0.094 lb AI/A gave 80% control of London rocket. Goal caused marginally acceptable injury (12 to 17 %) and Stinger caused minimal crop injury. Goal appears to be ineffective against weeds at less than 0.094 lb AI/A and crop safety is very marginal. Lentagran was relatively safe on broccoli and cabbage but did not control the existing weed spectrum.

Paraquat and diquat were effective against weeds immediately at 3 DAT. Glyphosate, sulfosate, and glufosinate exhibited activity against the weeds at 7 to 10 DAT. Paraquat provided the most complete weed control of most weeds at 10 to 16 DAT. Most of the diquat treated weed recovered and exhibited regrowth after 22 DAT. Glufosinate did not provide adequate control of most weeds at 22 DAT similar to diquat. Glyphosate and sulfosate were nearly equivalent at 0.50 and 2.0 lb AI/A against most weeds at most of the rating dates.

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No description available.

Giant reed (Arundo donax L.) is a candidate to provide feedstock for the Portland General Electric power plant in Boardman, Oregon. Giant reed is a fast perennial grass, producing 23-27 metric tons ha⁻¹ of biomass and has the ability to adapt to diverse environments making it a good candidate for biomass production. This study tested postemergence and preemergence herbicides for controlling weeds in giant reed during the establishment year in which giant reed plants are more sensitive to weed competition. The greenhouse study demonstrated that among the tested herbicides, bromoxynil plus MCPA at 0.841 kg ai ha⁻¹, nicosulforun at 0.035 kg ha⁻¹, and dimethenamid-p at 0.735 kg ha⁻¹ did not injure giant reed. In a field study, preemergence application of dimethenamid-p at 0.735 kg ha⁻¹ followed by a postemergence application of 2,4-D amine at 0.560 kg ha⁻¹ and a postemergence application of bromoxynil plus MCPA at 0.841 kg ha⁻¹ did not injure giant reed. The presence of weeds in a field does not always mean that crop yield will be reduced and there are some periods during the growing season when weeds will not cause considerable yield loss. Therefore, predicting a critical period of weed control (CPWC) that includes the best time for weed control in giant reed could improve weed management in the field. The length of the CPWC could be different depending on the level of acceptable yield loss (AYL). Our results are reported for AYL of 5 and 10%. The CPWC started at 290 accumulated growing degree days (GDD) and ended at 820 for a 5% AYL, while for a 10% AYL, it started at 333 GDD and ended at 727 GDD. Based on the results, there are some herbicides which could be selected for further study for weed control in the giant reed and the estimated CPWC which could be used to inform weed management practices in giant reed production. / Graduation date: 2013

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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Cirsium arvense (L.) Scop. (Canada thistle) is a persistent perennial pasture weed in Eastern Canada. Single control measures such as cultural, chemical, and biological methods are not effective in long term reduction of the weed population. The objectives of this research project were to evaluate the efficacy of various traditional control methods and to attempt to integrate them. / The effectiveness of Urophora cardui L. as a biological control agent is limited due to a lack of synchrony between the agent and the weed. This can be improved through integration with herbicides or mowing in time or space. Other biological control agents such as Orellia ruficauda Fab., Cassida rubiginosa Muell., and Puccinia punctiformis (Str.) Rhol. resulted in limited suppression of the weed population. Mowing was not effective in sustaining weed reductions for longer than one year. Application of clopyralid or 2,4-D/dicamba effectively reduced the weed population. The application of 3.37 kg a.i. ha$ sp{-1}$ 2,4-D/dicamba or 0.3 kg a.i. ha$ sp{-1}$ clopyralid with the spring and summer mowings were the most effective mowing/herbicide combinations over the two-year period.

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Two field studies examining direct ecological weed control practices were conducted in Lexington, Kentucky. The first evaluated weed control efficacy and influence on yields of several mulches in two organically-managed bell pepper (Capsicum annum) production systems for two years. Peppers were planted in double rows in flat, bare ground or on black polyethylene-covered raised beds with drip irrigation, and four mulches (straw, compost, wood chips, and undersown white dutch clover (Trifolium repens L.) living mulch) were applied to the two production systems. In both years, polyethylene-covered raised beds produced higher yields than the flat, bare ground system. In the second year, the polyethylene-covered bed system coupled with mulching in-between beds with compost or wood chips after cultivation provided excellent weed control and yields. The second field study evaluated the efficacy of soil solarization and shallow cultivation on the invasive and noxious weed johnsongrass over two years (Sorghum halapense). A soil solarization treatment, using clear plastic stretched over soil for eight weeks, and a cultivated bare fallow treatment, utilizing a tractor pulled cultivator implement equipped with sweep blades, were randomly applied during the summers of 2003 and 2004 to a field infested with johnsongrass. Solarized and cultivated plots in both years were lightly tilled 8 months after completion of the initial treatment period. At the conclusion of the experiment the johnsongrass population was significantly reduced in all treatments and in the control plots compared to the original infestation. These two experiments testing direct weed control practices (mulching, cultivation, solarization) were undertaken in the context of an ecological weed management plan that includes long term strategies to reduce weed infestations such as crop rotation, cover cropping, and fertility management that are essential for organic farmers.