Postemergence Control Of Broadleaf Weeds Research Articles

A systematic review of chemical weed management in peanut (Arachis hypogaea) in the United States: challenges and opportunities

AbstractHerbicides are the primary tool for controlling weeds in peanut (Arachis hypogaea L.) and are crucial to sustainable peanut production in the United States. The literature on chemical weed management in peanut in the past 53 yr (1970 to 2022) in the United States was systematically reviewed to highlight the strengths and weaknesses of different herbicides and identify current research gaps in chemical weed management. Residual weed control in peanut is achieved mainly with dimethenamid-P, ethalfluralin, pendimethalin, and S-metolachlor. More recently, the use of the protoporphyrinogen oxidase inhibitor flumioxazin and acetolactate synthase inhibitors, such as diclosulam, for residual weed control in peanut has increased considerably. Postemergence broadleaf weed control in peanut is achieved mainly with acifluorfen, bentazon, diclosulam, imazapic, lactofen, paraquat, and 2,4-DB, while the graminicides clethodim and sethoxydim are the major postemergence grass weed control herbicides in peanut. Although several herbicides are available for weed control in peanut, no single herbicide can provide season-long weed control due to limited application timing, lack of extended residual activity, variability in weed control spectrum, and rotational restrictions. Therefore, effective weed management in peanut often requires herbicide mixtures and/or sequential application of preplant-incorporated, preemergence, and/or postemergence herbicides. However, the available literature showed a substantive range in herbicide efficacy due to variations in environmental conditions and flushes of weed germination across years and locations. Despite the relatively high efficacy of herbicides, the selection of herbicide-resistant weeds is another area of increasing concern. Future research should focus on developing new strategies for preventing or delaying the development of resistance and improving herbicide efficacy within the context of climate change and emerging constraints such as water shortages, rising temperatures, and increasing CO2 concentration.

Fomesafen impacts bacterial communities and enzyme activities in the rhizosphere

Fomesafen, a long-lived protoporphyrinogen-oxidase inhibitor, specially developed for post-emergence control of broad-leaf weeds, is used widely in soybean fields in northern China (Dayan and Duke, 2010). The impact of fomesafen on microbial communities in rhizosphere soils, however, is unknown. In this study we examined fomesafen degradation as well as its effects in the rhizosphere of soybean plants grown in a greenhouse. Fomesafen had shorter half-life in rhizosphere soil than previously reported for bulk soil from the same location (87 vs 120 days). The enzyme activity of soil extracts and the microbial community composition of 16S rRNA genes (16S) amplified from soil DNA were also investigated. Although not immediately apparent, both the high (37.5 mg kg−1) and low (18.75 mg kg−1) doses of fomesafen significantly decreased urease and invertase activities in the rhizosphere soil from days 30 and 45 respectively until the end of the experiment (90 days). Analysis of 16S amplicons demonstrated that fomesafen had a dose dependent effect, decreasing alpha diversity and altering beta diversity. Significant phylum level decreases were observed in five of the ten phyla that were most abundant in the control. Proteobacteria was the only phylum whose relative abundance increased in the presence of fomesafen, driven by increases in the genera Methylophilacaea, Dyella, and Sphingomonas. The functional implications of changes in 16S abundance as predicted using PICRUSt suggested that fomesafen enriched for enzymes involved in xenobiotic metabolism and detoxification (cytochrome P450s and glutathione metabolism). Our data suggest that, despite being degraded more rapidly in the rhizosphere than in bulk soil, fomesafen had long-lasting functional impacts on the soil microbial community.

Postemergence Weed Control in Warm-season Turfgrass with a Mixture of Pyrimisulfan and Penoxsulam

Pyrimisulfan is a sulfonanilide herbicidal inhibitor of acetolactate synthase (ALS) used to control grass and sedge weeds of rice (Oryza stricta L.) production. Penoxsulam is an ALS-inhibiting herbicide that provides early postemergence control of broadleaf weeds in managed turfgrass. Separate field trials were conducted in Knoxville, TN, during Summer 2017 and 2018 to evaluate the efficacy of pyrimisulfan + penoxsulam for control of white clover (Trifolium repens L.), yellow nutsedge (Cyperus esculentus L.), wild violet (Viola spp.), ground ivy (Glechoma hederacea L.), and virginia buttonweed (Diodia virginiana L.) in common bermudagrass (Cynodon dactylon L.) and tall fescue (Festuca arundinacea Schreb.) turf. All treatments were applied on a granular fertilizer carrier (mean particle size, 1.5 mm) that contained 21% N : 0% P2O5 : 3% K2O. Treatments were applied at an early postemergence growth stage during April of each year and were irrigated into the soil within 24 hours of application. Weed control was assessed from 4 to 10 weeks after initial treatment (WAIT) relative to untreated control plots in each replication. White clover and wild violet were controlled effectively with pyrimisulfan + penoxsulam at 70 + 70 g·ha−1 whereas sequential applications at either 70 + 70 g·ha−1 followed by 35 + 35 g·ha−1 or 52.5 + 52.5 g·ha−1 followed by 52.5 + 52.5 g·ha−1 were needed to control yellow nutsedge, ground ivy, and virginia buttonweed effectively. Future research should explore long-term control of these species, particularly wild violet, ground ivy, and virginia buttonweed with pyrimisulfan + penoxsulam applied over multiple seasons. Chemical names: 2′-[(4,6-dimethoxypyrimidin-2-yl)(hydroxy) methyl]-1,1-difluoro-6′-(methoxymethyl)methanesulfonanilide (pyrimisulfan); 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy1,2,4triazolo 1.5-c-pyrimidin-2-yl)-6-(trifluoromethyl)benzenesulfonamide (penoxsulam).

Light-Activated, Sensor-Controlled Sprayer Provides Effective Postemergence Control of Broadleaf Weeds in Fallow

A study was conducted in summer fallow fields near Davenport, WA, and Pendleton, OR, in 2007 and 2008 to evaluate the POST weed control efficacy of herbicide treatments applied with a light-activated, sensor-controlled (LASC) sprayer compared to the broadcast application of glyphosate. The LASC application of glyphosate alone (at all rates) and in mixture with pyrasulfotole plus bromoxynil or 2,4-D had weed control (≥ 88%) and dry weight (≤ 6% of control) similar to the broadcast application of glyphosate across locations and years. Tumble pigweed and prickly lettuce control with bromoxynil, 2,4-D, or carfentrazone plus dicamba, was 12 to 85% less than glyphosate applied alone with LASC or broadcast sprayer. Overall, none of the tested alternate herbicides was promising enough to replace glyphosate under present conditions.

Narbon bean (Vicia narbonensis) agronomy in south-western Australia

Narbon bean (Vicia narbonensis L.) shows promise as a fodder, green manure and grain crop in south-western Australia. This study examines the effect of time of sowing (2 experiments), plant density (3 experiments) and reaction to herbicides (4 experiments on tolerance to herbicides and 1 experiment on removing narbon bean from a wheat crop) in 10 separate field experiments sown at 4 locations in the mallee region of Western Australia from 1998 to 2001. Narbon bean was found to be unresponsive to changes in sowing date with yield maintained until the first week of June. The optimum plant density (90% of fitted maximum) for seed yield was found to be 31 plants/m2, equivalent to sowing rates in the range of 75–100 kg/ha. A wide range of herbicides applied either before sowing or immediately after sowing and before emergence had no significant effect on grain yield. These included simazine (750 g a.i./ha), cyanazine (1.25 kg a.i./ha) and diuron (500 g a.i./ha), which were applied immediately before sowing, and imazethapyr (29 g a.i./ha), which was applied after sowing, before emergence. Diflufenican (75 g a.i./ha) was found to be the only available option for post-emergence control of broadleaf weeds. The use of the non-selective herbicides glyphosate (450 g a.i./L) and Sprayseed 250 (paraquat 135 g a.i./L and diquat 115 g a.i./L) as post-emergence herbicides was found to be unpredictable at a range of application rates. Results ranged from a yield loss of 47% to a yield increase of 23%. In an experiment to test a range of herbicides for the selective control of narbon bean within a wheat crop, numerous herbicides were found to effectively remove volunteer narbon bean indicating that narbon bean is unlikely to become a weed in most cereal cropping systems.

History of Sugarbeet (Beta vulgaris) Herbicide Rate Reduction in North Dakota and Minnesota

Phenmedipham was registered for use at 1.1 to 1.7 kg ai/ha in 1970 and desmedipham at 1.1 to 1.4 kg ai/ha in 1974 for postemergence control of broadleaf weeds in sugarbeet. Phenmedipham was sold from 1970 through 1981 and desmedipham plus phenmedipham (1:1), as a premixed product, has been sold since 1982. Development of multiple applications of reduced rates began in 1972 primarily to reduce sugarbeet injury. The technique was promoted to farmers after 1976. Ahalf-rate of phenmedipham and/or desmedipham applied twice at a 5- to 7-d interval controlled weeds better and caused less sugarbeet injury than a single full-rate application, and allowed application to smaller than four-leaf sugarbeet. Suggested sugarbeet size for the first application changed from 4-leaf in 1970 to cotyledon to two-leaf in 1992. Earlier application to more susceptible small weeds allowed a further rate reduction. The use of soil-applied herbicides prior to phenmedipham and/or desmedipham increased weed control and sugarbeet injury. Application to small weeds and sugarbeet by air or by ground sprayers at spray pressures over 1040 kPa controlled weeds better and injured sugarbeet more than when applied by ground sprayers at 280 kPa. Desmedipham and phenmedipham rates presently are adjusted for sugarbeet size, application method, soil-applied herbicide, and environment. The suggested initial application rate of phenmedipham and/or desmedipham in 1992 was 0.13 to 0.28 kg/ha as compared with 1.1 to 1.7 kg/ha in 1970. A typical rate of desmedipham or desmedipham plus phenmedipham applied in 1992, including multiple application, was approximately 0.7 kg/ha less than typical rates from 1970 through 1977.

Control ofCruciferaeWeeds in Canola (Brassica napus) with DPX A7881

Postemergence control of broadleaf weeds in canola with DPX A7881 was studied under controlled-environment and field conditions. DPX A7881 controlled weeds of theCruciferaefamily such as wild mustard, field pennycress, and flixweed, which are not controlled with existing herbicides used for weed control in canola. Weed control was better when DPX A7881 was applied at the two-leaf than at the six-leaf stage of the weeds. At the two-leaf stage, control of flixweed was achieved with 15 g ai/ha of DPX A7881; 20 to 30 g ai/ha was required for control of wild mustard and field pennycress. Control of redroot pigweed required 30 g ai/ha. Common lambsquarters was not controlled in this study with DPX A7881 up to 60 g ai/ha. Control of weeds with DPX A7881 increased canola yields in this study without altering the important quality components: oil content, 1000-kernel weight, and green seed content. DPX A7881 provides a postemergence alternative to existing herbicides for broadleaf weed control in canola.