Factors affecting benfuresate activity against purple nutsedge (Cyperus rotundas L.)

Benfuresate (2-3-dihydro-3,3-dimethylbenzofu-ran-5-yl ethanesulfonate) is a selective herbicide for the control of purple nutsedge in cotton. Under outdoor conditions, purple nutsedge was sensitive to benfuresate incorporated in soil up to eight days after initiation of shoot sprouting from the tuber. Older seedlings recovered from the damage. During the period of susceptibility to benfuresate, young shoots more sensitive than the roots. Under controlled environmental conditions, benfuresate applied directly to apical buds developing from the tuber caused severe damage to the treated bud and induced abrupt development of axillary buds. Negligible amounts of the applied herbicide were translocated from the treated part to the other buds and roots. Application of the herbicide to fully developed leaves had no effect, probably because of its rapid metabolism and low basipetal mobility. Its relatively high volatility may also contribute to its low foliar post-emergence activity. Tubers also absorbed herbicide vapours. Root uptake of ¹⁴C-benfuresate resulted in a rapid accumulation of ¹⁴C in the shoot, which had no effect on the purple nutsedge plant, regardless of concentration. The herbicide is rapidly converted, mainly to a non-phytotoxic polar product. These results may explain the high sensitivity of the weed to benfuresate at early growth stages, and the lack of sensitivity in mature plants.     

The use of fomesafen for pre-emergence weed control in cotton

The herbicide fomesafen was found to be selective in preplanting and pre-emergence treatments in cotton (Gossypium hirsutum L.). It was effective due to residual soil activity in controlling some of the most troublesome weeds in cotton fields,i.e., pigweed (Amaranthus spp.), black nightshade (Solarium nigrum L.), velvetleaf (Abutilon theophrasti Medik.) and cocklebur (Xanthium spp.). The best soil activity of fomesafen was achieved from pre-emergence or preplanting applications which were activated when the soil was wetted by rain or sprinkler irrigation, but the herbicide caused damage to the crop’s foliage if rain fell just after the cotton emergence. The most effective and safest method for applying fomesafen in cotton fields was preplanting followed by mechanical incorporation to a depth of 10 cm. Combinations of fomesafen with trifluralin were effective and completed the spectrum of controlled weeds in cotton, including annual grasses, common purslane (Portulaca oleracea L.) and field bindweed (Convolvulus arvensis L.).     

Tillage and herbicide treatments with inter‐row cultivation influence weed densities and yield of three industrial crops

Field experiments were conducted in northern Greece in 2003 and 2004 to evaluate effects of tillage regimes (moldboard plowing, chisel plowing, and rotary tilling), cropping sequences (continuous cotton, cotton‐sugar beet rotation, and continuous tobacco) and herbicide treatments with inter‐row hand hoeing on weed population densities. Total weed densities were not affected by tillage treatment except that of barnyardgrass (Echinochloa crus‐galli), which increased only in moldboard plowing treated plots during 2003. Redroot pigweed (Amaranthus retroflexus) and black nightshade (Solanum nigrum) densities were reduced in continuous cotton, while purple nutsedge (Cyperus rotundus), E. crus‐galli, S. nigrum, and johnsongrass (Sorghum halepense) densities were reduced in tobacco. A. retroflexus and S. nigrum were effectively controlled by all herbicide treatments with inter‐row hand hoeing, whereas E. crus‐galli was effectively reduced by herbicides applied to cotton and tobacco. S. halepense density reduction was a result of herbicide applied to tobacco with inter‐row hand hoeing. Yield of all crops was higher under moldboard plowing and herbicide treatments. Pre‐sowing and pre‐emergence herbicide treatments in cotton and pre‐transplant in tobacco integrated with inter‐row cultivation resulted in efficient control of annual weed species and good crop yields. These observations are of practical relevance to crop selection by farmers in order to maintain weed populations at economically acceptable densities through the integration of various planting dates, sustainable herbicide use and inter‐row cultivation; tools of great importance in integrated weed management systems.     

The uptake,translocation and metabolism of epronaz in selected species

The absorption, translocation and metabolism of the selective pre- or early post- emergence herbicide epronaz (N-ethyl-N-propyl-3-propylsulphonyl-1,2,4-triazole-1-carboxamide) were investigated using selected crop and weed species. The pattern of tolerance to epronaz of both germinating seeds and 10-day-old plants grown in nutrient solution, was found to be soybean (Glycine max L.) > maize (Zea mays L.) > cotton (Gossypium hirsutum L.) > rice (Oryza sativa L.) > barnyard grass [Echinochloa crus-galli (L.) Beauv.]. In all species, absorption and translocation of ¹⁴C from a nutrient solution containing [¹⁴C]epronaz (0.02 μCi ml^?1) increased with time. Autoradiographic and liquid scintillation analysis indicated the presence of radioactivity in the apical regions of all species after 4 h. Interspecies variation in uptake and distribution did not appear to be a major factor explaining selectivity, although the resistance of cotton may be partly due to compartmentalisation of ¹⁴C in the lysigenous glands in stem and leaves. Analysis of extracts from plants treated with [¹⁴C]epronaz indicated the presence of epronaz, its major degradation product [3-propylsulphonyl-l,2,4-triazole (BTS 28 768)] and certain unknown radio-labelled compounds. The major metabolite (Unknown I) was believed to be a conjugate of certain plant components with either epronaz or BTS 28 768. The rate of formation of Unknown I corresponded to the relative resistance and susceptibility to epronaz of soybean, rice and barnyardgrass. The level of the herbicide remained much higher in cotton than in the other species, possibly reflecting compartmentalisation and inactivation of epronaz in the lysigenous glands. For maize, high levels of uptake, exudation and degradation in the nutrient solution were recorded.     

Metabolic fate of methazole in purple and yellow nutsedge

The mechanisms for the tolerance of purple nutsedge (Cyperus rotundus L.) and susceptibility of yellow nutsedge (Cyperus esculentus L.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] were studied. Both species absorbed and translocated[¹⁴C]methazole and metabolites from nutrient solution; however, greater amounts of ¹⁴C per unit weight were detected in yellow than in purple nutsedge. Although intact plants and excised leaves of both species rapidly metabolized methazole to DCPMU [1-(3,4-dichlorophenyl)-3-methylurea], detoxification of DCPMU to DCPU [1-(3,4-dichlorophenyl) urea] occurred more slowly in yellow than in purple nutsedge. Compared to yellow nutsedge, a greater percentage of the radioactivity in purple nutsedge was recovered as polar products. Polar products were converted to the free forms of the parent herbicide and to phytotoxic DCPMU by proteolytic enzyme digestion. Based on the findings of this study, at least three mechanisms (differential absorption, metabolism, and formation of polar products) account for the differential tolerance of these two species to methazole.     

Glyphosate injury on Cyperus esculent us leaves and basal bulbs: histological study

The effect of glyphosate on leaves and basal bulbs of yellow nutsedge (Cyperus esculentus L.) plants was studied. Treatment with glyphosate did not affect leaf anatomy, although light necrotic spots were seen on the veins. In contrast, basal bulb organization was greatly affected with large necrotic zones and disorganization in the vascular cylinder due to herbicide accumulation. Depletion or disappearance of vacuolar phenols was observed in bulbs of plants treated with the highest doses of glyphosate. The most remarkable effect of glyphosate was the appearance of one layer of sclerenchymatic cells between root and rhizome primordia and the cortical tissues which could play an important role in the inhibition of rhizome and root emergence by the herbicide.     

Interaction between purple nutsedge,maize and soybean

The study was designed to determine the mode of interaction between maize ( Zea mays L.) and soybean ( Glycine max Merr.) in association with purple nutsedge. This was investigated under glasshouse conditions using the replacement (substitutive) series design. Maize and soybean competed with purple nutsedge for growth resources, and purple nutsedge significantly retarded the growth and development of maize and soybean. Maize was more susceptible to purple nutsedge interference compared with soybean.     

Growth and reproduction of Cyperus esculentus L. and Cyperus rotundus L.

The growth of both species (as characterized by their total dry weight, inflorescence dry weight, root and rhizome dry weight and number of shoots per pot) was similar, but they differed in the manner in which the dry weight was partitioned to reproductive structures. Each species partitioned less than 2% of its dry weight into floral formation. However, yellow nutsedge (Cyperus esculentus L.) partitioned only 28% of its dry weight to tubers, whereas purple nutsedge (C. rotundus L.) partitioned 50% of its dry weight to fewer and larger tubers. The allocation of dry weight to reproductive structures was related to changes in day-length. Yellow nutsedge tuber formation increased as day-length decreased from 14.5 to 12.5 h, while floral formation did not begin until the day-length dropped below 14 h. Purple nutsedge formed inflorescences earlier and production continued throughout the remainder of the study, but tuber formation was curvilinear and accelerated as the day-length decreased.     

Influence of propaquizafop application rate and time on Sorghum halepense (L.) Pers. control and cotton (Gossypium hirsutum) yield

Field experiments were carried out from 1990 through 1992 to study the effect of propaquizafop application rate and application timing of fluazifop, haloxyfop, propaquizafop, quizalofop, and hoeing on Sorghum halepense (L.) Pers. control and seed cotton yield. Control of S. halepense with propaquizafop applied to plants 20–35 cm tall was not affected by rate of application and was similar to that obtained with fluazifop applied at the recommended rate. Cotton yield following all herbicide treatments was greater than that of the weedy control, but lower than that of the weedfree control. S. halepense control with fluazifop, haloxyfop, propaquizafop, and quizalofop applied to plants 20–35 or 35–80 cm tall was greater than that obtained with their application to plants 5–15 or 10–25 cm tall. Ho-eing, applied once at any S. halepense growth stage, provided less control than any herbicide treatment on the same date. Cotton yield was increased by all herbicide treatments and hoeing compared to that of the weedy control, but the highest yield was obtained after herbicide appli-cation to S. halepense plants 10–25 cm tall. However, none of the herbicide treatments or hoeing increased cotton yield to the level of the weedfree control.     

The Royal Show

Abstract

A non-mechanical system of applying herbicides to weeds taller than crops by a simple rope wick device is described. The herbicide applicator requires no pumps or moving parts to deliver the herbicide, and it can be built by the farmer at a very low cost. Selective control of johnsongrass (Sorghum halepense (L.) Pers.) in soyabeans (Glycine max (L.) Merr.) with glyphosate was demonstrated in two experiments under field conditions.     

Dinitroaniline Herbicide Cross-Resistance in Resistant Setaria italica Lines Selected from Interspecific Cross with S. viridis

Breeding of herbicide-resistant foxtail millet (Setaria italica (L.) Beauv.) is desirable in modern agriculture because no selective herbicide is available for this crop. Trifluralin-resistant millet lines obtained from a interspecific cross between a resistant green foxtail (Setaria viridis (L.) Beauv.) and a foxtail millet cultivar were tested for response to five dinitroaniline herbicides in greenhouse and field experiments. The results in the greenhouse study showed that the resistant type was cross-resistant to all tested herbicides. ED₅₀ values indicated that the highest resistance was obtained with trifluralin, the resistant biotype being seven and 33 times more resistant than the parent cultivar at the emergence and seedling stages, respectively. However, the doses recommended for efficient weed control resulted in some detrimental effects on emergence and growth in the field. Strategies for use of this resistance to control weeds in millet fields are proposed. © 1997 SCI.     

Control of johnsongrass (sorghum halepense) in cotton fields

Control of johnsongrass (Sorghum halepense (L.) Pers.) in cotton fields was achieved by the combined action of two herbicides: 1.5 kg/ha trifluralin incorporated preplanting prevented emergence of seedlings throughout the cotton growth season and reduced the vigor of rhizomes; and 1.25 kg/ha fluaziflop applied postemergence to the cotton crop selectively inhibited the growth of established rhizomes of the grass and completed the control. Reducing the spray volume for fluazifop from 300 to 200 1/ha resulted in efficient control of johnsongrass with lower rates of the herbicide.     

Weed flora and seed yield in quinoa crop (Chenopodium quinoa Willd.) as affected by tillage systems and fertilization practices

The effects of tillage system and fertilization regimes on weed flora in quinoa (Chenopodium quinoa Willd.) were evaluated by means of two field experiments in 2011 and 2012. The experiments were laid out in a split-plot design with two main plots (conventional and minimum tillage) and four sub-plots (fertilization regimes). The results indicated that weed biomass and density in quinoa were influenced by the different fertilization and tillage treatments. Moreover, seed yield in conventional was 5%–13% higher than that of minimum tillage, probably due to the lower weed density and biomass. Concerning fertilization treatments, total weed density and biomass increased under manure application and inorganic fertilization. Tillage effects on weeds were species specific. The density of perennial weeds such as purple nutsedge (Cyperus rotundus L.) and the density of small-seeded weeds such as redroot pigweed (Amaranthus retroflexus L.) and common purslane (Portulaca oleracea L.) were significantly lower under the conventional tillage than under the minimum tillage system.     

INCORPORATED VERSUS SUBSURFACE VERNOLATE FOR WEED CONTROL TN PEANUTS*

Summary. Under dry field conditions, vernolate (S-propyl dipropylthiocarbamate) incorporated by conventional methods controlled less yellow nutsedge (Cyperusesculentus L.) and injuied peanuts (Arachis hypogaea L., groundnuts) more than when injected in lines under the soil or subsurface-applied through sweep applicators. In glasshouse studies, vernolate eliminated production of new nutsedge tubers if it was applied below the soil surface either 1 in. above or 1 in. below the parent tuber. Method of placement was less critical in determining control of most annual weeds. When averaged over two soil types and 2 years, peanuts yielded 14% more after subsurface applications than after incorporated treatments of vernolate. In comparison with the optimum subsurface placement, the yield from incorporation was significantly lower in three of four field studies, the reduced yields probably resulting from a combination of herbicide injury and poor weed control. Factors affecting the distribution of vernolate vapours (such as method of placement, soil type and amount of rainfall after treatment) apparently determine the differential toxicity of this herbicide. Neither market quality nor germination of peanut seed was adversely affected by vernolate treatment.     

Chemical control of perennial nutsedge (Cyperus rotundus L.) in tropical upland rice

Five herbicides were tested in the dry and in the wet season for their effectiveness in conlrolling perennial nutsedge (Cyperus rotundus L.) in direct-seeded upland rice in the tropics. K-223 [N-(α,α-dimethylbenzyl)-N'-P-tolyl urea] gave the best results. When broadcast sprayed at 8.0 kg a.i./ha in the dry season and 10 kg a.i./ha in the wet season and immediately mixed into the soit just before drilling, K-223 gave excellent perennial nutsedge control with no visible crop damage and increased the grain yield. Bentazone at 2.0 kg a.i./ha applied 7 days after crop emergence was highly selective and gave fair control of nutsedge without being toxic to the crop. MBR 8251 [1.1,1-trifluoro-4′-(phenylsulfonyl) methane-sulfono-o-toluidide] at 2.0 kg a.i./ha, mecoprop (MCPP) at 1.5 kg a.c./ha and fenoprop (silvex) at 1.0 kg a.e./ha applied 7, 14 and 7 days, respectively after crop emergence provided a fair degree of nutsedge control. Fenoprop and MBR 8251 caused slight and mecoprop moderate initial toxicity, but the injury sustained did not significantly affect crop yield.     

Herbicide antidotes—A review

The history of herbicide antidotes is reviewed, beginning with the exploration of compounds to protect wheat (Triticum aestivum L.) against barban in the early 1960s, and the later introduction of naphthalic anhydride (NA, naphthalene-1, 8-dicarboxy-licanhydride) as a seed dressing for protecting maize (Zea mays L.) against EPTC. This compound was largely replaced by Stauffer's R-25788 (N, N-diallyl-2, 2-dichloroacetamide) which has continued to be widely used in conjunction with EPTC and butylate in maize. This compound is highly specific to maize and can thus be applied in admixture with the herbicide, but has not proved of practical value on other crop species. NA on the other hand is less specific and is of potential value on sorghum [Sorghum bicolor (L.) Moench] and rice (Oryza sativa L.); experimental work continues on these crops. The only other antidote to be marketed so far is cyometrinil as a seed dressing for protecting sorghum against metolachlor and related herbicides. Other compounds are under development. Mode of action and structure-activity relations are discussed, as well as the current and future potential for antidotes in respect of the control of weed species in closely related crops, the increased options for herbicide use in minor crops and the possibility of reduced costs for broad spectrum weed control in major crops.     

Control of Solatium karsensis in grain sorghum

Solatium karsensis Symon, an Australian native perennial, has become an important weed in irrigated summer crops in far western New South Wales. A screening trial of 14 herbicides showed that atrazine was the most effective treatment, though 2,4-D also suppressed S. karsensis in grain sorghum (Sorghum bicolor L. cv. Rico) for the duration of the crop. Grain sorghum yields were higher in plots treated with atrazine at 2–5 kg (a.i.) ha^?1 than for any other herbicide treatment or the untreated control. Because the root system remained viable annual herbicide application would be necessary for the continued control of 5. karsensis.     

Sodium 2,2,3,3-tetrafluoropropionate,a New Herbicide for Jute Field Weeds

Abstract

Sodium 2,2,3,3-tetrafluoropropionate (TFP) was tested as pre-planting and post-emergence applications on jute heavily infested with grasses and sedges. The herbicide was applied by two methods, at several rates and at different times before sowing. As a post-emergence application it was sprayed over a three week old crop. The best results were obtained when the herbicide was incorporated into the soil ten days before sowing at 3–4 kg a.i./ha. This practice controlled all grasses and sedges except nutsedge, which was only reduced by 30–40%, although higher rates gave better control. No phytotoxic effects on jute were observed with this rate and method of application.     

Efficacy of chemical weed control in spring cereals in Finland

A national survey was conducted in Finland from 1982 to 1984 to determine the main weed species in spring cereals and the efficacy of herbicides on Finnish farms. The most common dicotyledonous weeds producing the highest biomass in spring cereals were Chenopodium album L., Galeopsis spp. L., Stellaria media (L.) Vill. and Lapsana communis L. The main grass weed was Elymus repens (L.) Gould. The average reduction of weed biomass by herbicide treatment was 75%. More reliable efficacy was obtained with herbicide mixtures than with MCPA alone.     

Studies on the selectivity of alloxydim-sodium in plants

Alloxydim-sodium, methyl 3-[1-(allyloxyimino)butyl]-4-hydroxy-6,6-dimethyl-2-oxocyclohex-3-enecarboxylate sodium salt, is a selective herbicide which controls grass weeds in a wide range of broad-leaf crops. Spray retention, tested at two growth stages, was generally greater for the broad-leaf crops (cotton, sugarbeet, flax, beans and peas) than for wild oat (Avena fatua L.), blackgrass (Alopecurus myosuroides Huds), barley and couch grass [Agropyron repens (L.) Beauv.], and did not contribute to selectivity between susceptible and tolerant species. Broad-leaf crops tolerated 2820 g alloxydim-sodium ha^?1, three times the recommended rate used to control annual grasses. Differential uptake and translocation were not factors contributing to selectivity. In wild oat, blackgrass and sugarbeet, uptake and translocation of ¹⁴C continued during a period of 14 days after treatment with [¹⁴C]alloxydim-sodium. Translocation in susceptible and tolerant species was predominately symplastic. Over 40% of the applied ¹⁴C was eliminated from treated wild oat, blackgrass and sugarbeet plants within 7 days, due to degradation and volatilisation. A greater proportion of the methanol-soluble radioactivity extracted from leaves and roots was present as water-soluble polar metabolites in sugarbeet, than in wild oats, 7 days after treatment. The proportion of unaltered alloxydim in the organo-soluble fraction of a methanol extract was greater in wild oat than in sugarbeet. Differential metabolism appears to be one of the factors contributing to alloxydim-sodium selectivity between sugarbeet and wild oat.