A new model membrane system for the investigation of penetrative properties of plant growth substances

A new model membrane system has been developed which simulates in many ways the behaviour of a plant cell membrane. It is very suitable for studying the penetration and associated effects of plant growth substances because of its large size (4.9±0.3 cm²), its ease of preparation and its reproducible properties. It consists of a Millipore filter disc impregnated with egg yolk lecithin, n-octanol and n-tetradecane. The effect of a number of plant growth and allied compounds on membrane conductivity at 25±0.5°c has been assessed by the addition of various concentrations of these substances to the solutions (0.01 M-NaCl) on each side of the membrane. Certain compounds present in the solutions (pH 3.0) in the concentration range 10^?4 M to 10^?3 M considerably reduced the membrane conductivity. This effect was seen to be related to the structure of the hydrophobic portion of the molecule. The flux through the membrane at 25±0.5°c of various organic substances (2,4-D, benzoic acid, benzyl alcohol, benzamide and benzaldehyde) was measured for membranes containing no lecithin and compared with the flux obtained in comparable experiments, with lecithin present in the membrane. The presence of lecithin increased the flux, and the percentage increase was used to assess in each case the part played by lecithin in transport. The flux of 2,4-D was much greater at low pH values. A possible interpretation of these phenomena is suggested.     

N-Nitrosodimethylamine content of aqueous dimet hylamine and phenoxy herbicide/dimethylamine formulations during storage

N-Nitrosodimethylamine (NDMA) levels in samples of 600 g litre^?1 aqueous dimethylamine (DMA) solution stored at 4, 25 and 40°C, in formulations of the DMA salt of 2, 4-dichlorophenoxyacetic acid (2, 4-D) and of the DMA salt of 4-chloro-2-methylphenoxyacetic acid (MCPA) at 40°C were monitored using a gas-liquid chromatograph coupled with a thermal energy analyser (g.l.c./t.e.a.). The NDMA content of aqueous DMA at 4°C increased from 0.32μgg^?1 to 8.6μgg^?1 in 156 days. At 25°C it increased from 0.20μgg^?1 to 10.5 μgg^?1 in 156 days and at 40°C from 0.76μgg^?1 to 7.12μgg^?1 in 54 h. At 40°C, the NDMA in the 2, 4-D/DMAsalt increased from 0–53μgg^?1 to 2.79μgg^?1 in 96 days and in the MCPA/DMA salt from 0.48μgg^?1 to 5.51 μgg^?1 in 21 days.     

Hydrolysis of the pyrethroid insecticide fenpropathrin in aqueous media

The hydrolysis of [¹⁴C] fenpropathrin ( I ) [(RS)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate] was studied in buffer solutions at pH 1.9–10.4, and in natural river and sea water at 25, 40, 55 and 65°C under laboratory conditions. The hydrolysis of I proceeded predominantly through neutral (pH independent) and base-catalysed processes in the regions below pH 3.9 and above pH 7.0, respectively, whereas both reactions occurred between pH 3.9 and 7.0. The rates of hydrolysis of I in buffer solutions were similar to those in one sample of river and one sample of sea water. If this obtains generally, it may be expected that the half-life of I in natural waters, normally within the range pH 5–9, will range from 1.54 to 1080 days at 40°C, 11.3 to 8520 days at 25°C and, by extrapolation of the data obtained in buffer solutions, 106 to 83 000 days at 10°C. The rate constants for hydrolysis of I in aqueous media can be expressed by: Where log k_N = 9.60–(5.56 × 10³ T^?1) and log k_B = 7.32–(2.56 × 10³ T^?1). The calculated rate constants were in good accord with the observed values in buffer solutions. Cleavage of the ester linkage was more rapid than hydration of the cyano group at any pH and temperature tested.     

Breakdown rates of dimethoate in fruit and vegetable dips

In order to determine the effect of pH and temperature on post-harvest dip solutions of dimethoate (500 mg litre^?1), the half-lives and pseudo first-order rate constants were calculated from measurements at pH 4, 6, 8, 10, 11.5, and at two temperatures 25 and 52°C. The half-lives ranged from 206 days to 39.3 min at 25°C, and from 5.6 days to 205s at 52°C; the rate constants ranged from 3.9 × 10^?8 s^?1 to 2.9 × 10^?4 s^?1 at 25°C, and from 1.4 × 10^?6 s^?1 to 3.4 × 10^?3 s^?1 at 52°C. The results show that the water used in dips should have a pH≤7. The addition of benomyl to the dip solutions at two concentrations (0.5 and 1.0 g litre^?1) had no effect on the half-lives and rate constants. The use of hard and salted waters in dips also showed no major effect. A formula was developed that gives the half-life of the dimethoate as a function of the pH and temperature.     

The biochemical mechanism of action of the dinitroaniline herbicide oryzalin

Dinitroaniline herbicides such as oryzalin (3,5-dinitro-N⁴,N⁴-dipropylsulfanilamide) disrupt mitosis in the meristematic cells of seedling plants by inhibiting the formation of microtubules. For further understanding of the biochemical mechanism of action of oryzalin, laboratory analyses with isolated plant tubulin must be employed. Plant tubulin from flagella of the alga Chlamydomonas was isolated and purified. This tubulin was incubated with [¹⁴C]oryzalin, and free oryzalin was separated from oryzalin bound to plant tubulin by miniature DEAE-cellulose chromatography. Scatchard analysis predicts a molar ratio of oryzalin bound to plant tubulin of 1.0 ± 0.1 when oryzalin is incubated with plant tubulin for 30 min at pH 6.9 and 25°C. The association constant for the oryzalin-tubulin complex is 2.08 ± 0.08 × 10⁵M^?1 at 25°C. The thermodynamic values for the formation of the oryzalin-tubulin complex at 25°C are ΔG^o = ?7.25 ± 0.02 kcal mol^?1, ΔH^o = 6.5 ± 0.2 kcal mol^?1, and ΔS^o = 46 ± 2 cal mol^?1 deg^?1 (mean ± standard error). Oryzalin has little or no affinity for intact microtubules, previously denatured plant tubulin, actin, bovine serum albumin, calmodulin, ferredoxin, trypsin, or urease, indicating oryzalin is specific for the biologically active conformation of plant tubulin. Oryzalin binds to plant tubulin to form a complex that may be incapable of polymerizing into microtubules.     

Hydrolysis of the triazine herbicide,cyanazine

The hydrolysis of cyanazine

1 Cyanazine is the proposed common name for the herbicide sold under the Shell registered trade name BLADEX.

(2-chloro-4-cyanoisopropylamino-6-ethylamino-1,3,5-triazine) has been studied using ¹⁴C-ring labelled compound over a temperature range of 25° to 75 °C and over a range of pH values from 1.5 to 12. The activation energies and the activation entropy changes during hydrolysis showed there was a different mechanism under acid and alkaline conditions. The only product identified after hydrolysis in acid solutions was 2-hydroxy-4-carboxyisopropylamino-6-ethylamino-1,3,5-triazine. In alkaline solution the same hydroxy-acid was the end-product, but 2-chloro-4-amidoisopropylamino-6-ethylamino-1,3,5-triazine was isolated as an intermediate. The variation of the specific rate constants with temperature for hydrolytic catalysis by H⁺, OH^? was determined, thus enabling the hydrolytic half-life of cyanazine to be calculated at any pH and temperature.     

Effect of low temperatures on 2,4-D behaviour in maize plants

The foliar surface of 4-leaf maize plants was found to be poorly wettable and retained 106 μl g^?1 dry matter when sprayed with a U46D (2,4-D formulation) blank. The third leaf retained 141 μl g^?1. A 7-day cold spell (17/9°C) increased retention per unit dry matter by 53% (135% on the third leaf). Cold stress lowered epicuticular wax quantity by 29% on the third leaf. Contact angles of formulated 2,4-D lay between 115 and 125° and were not significantly affected by cold stress. 2,4-D rapidly entered into maize third leaf (66% in 24 h) but migration from it was less than 1.5%. 2,4-D was readily degraded in maize (80% in 72 h). The most abundant metabolite was probably an ester conjugate; little of the hydroxy derivatives were found. Cold stress reduced 2,4-D degradation, and 72 h after treatment the amount of undegraded 2,4-D was 78% higher in cold-stressed maize plants. It was concluded that 2,4-D selectivity in maize results from low spray retention per unit dry matter and active degradation of penetrated herbicide. Cold stress affects both factors.     

Kinetic Study of the Degradation of Ethiofencarb in Aqueous Solutions

A kinetic study of the hydrolysis of ethiofencarb (α-ethylthio-o-tolyl methylcarbamate) in pure water and in aqueous solutions at pH 2, 6, 9 and 12 and at three different temperatures (4, 20 and 50(±1)°C) has been carried out using a gas chromatographic nitrogen-phosphorus detection method. The values of the first-order rate constants (k) for the degradation reaction were calculated. The values for k were found to be dependent on pH and temperature. No acid hydrolysis was observed in any case. Complete degradation of ethiofencarb was observed at pH 12 at all three temperatures; it was practically instantaneous at room temperature. Ethiofencarb was also completely degraded at pH 9 at 20 and 50°C, while in pure water (pH 6) degradation took place at 50°C but not at 20°C. Ethiofencarb was not degraded in pure water at lower temperatures and, due to the reversible nature of the reaction, at equilibrium about 80% of the pesticide remained undegraded at room temperature. © 1997 SCI.     

Hydrolyse chimique acide du metsulfuron méthyle

Chemical acidic hydrolysis of metsulfuran methyl The chemical degradation of metsulfuron methyl in acidic aqueous solution involved two pathways: hydrolysis of the urea function and hydrolysis of methoxy radical. Decrease of pH (6 to 1) strongly increased activity but selectivity remained unchanged. Increase of temperature (25 to 55°C) enhanced the rate of reaction (E_A= 84 kj mol^?1) and favoured the urea function hydrolysis. Other factors (presence of various transition metals cations, humic acids or clays) were generally of limited effect, sometimes the rate of reaction was affected.     

Potential of piperonyl butoxide‐synergised pyrethrins against psocids (Psocoptera: Liposcelididae) for stored‐grain protection

BACKGROUND: Piperonyl butoxide (PB)‐synergised natural pyrethrins (pyrethrin:PB ratio 1:4) were evaluated both as a grain protectant and a disinfestant against four Liposcelidid psocids: Liposcelis bostrychophila Badonnel, L. entomophila (Enderlein), L. decolor (Pearman) and L. paeta Pearman. These are key storage pests in Australia that are difficult to control with the registered grain protectants and are increasingly being reported as pests of stored products in other countries. Firstly, mortality and reproduction of adults were determined in wheat freshly treated at 0.0, 0.75, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) at 30 ± 1 °C and 70 ± 2% RH. Next, wheat treated at 0.0, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) was stored at 30 ± 1 °C and 70 ± 2% RH and mortality and reproduction of psocids were assessed after 0, 1.5, 3 and 4.5 months of storage. Finally, the potential of synergised pyrethrins as a disinfestant was assessed by establishing time to endpoint mortality for adult psocids exposed to wheat treated at 3 and 6 mg kg^?1 of synergised pyrethrins after 0, 3, 6, 9 and 12 h of exposure. RESULTS: Synergised pyrethrins at 6 mg kg^?1 provided 3 months of protection against all four Liposcelis spp., and at this rate complete adult mortality of these psocids can be achieved within 6 h of exposure. CONCLUSION: Piperonyl butoxide‐synergised pyrethrins have excellent potential both as a grain protectant and as a disinfestant against Liposcelidid psocids. Copyright © State of Queensland, Department of Employment, Economic Development and Innovation, 2010. Published by John Wiley and Sons, Ltd.     

Mechanism of cellular absorption of imidazolinones in soybean (Glycine max) leaf discs

The mechanism of uptake of imazapyr, imazethapyr, and imazaquin into soybean leaf discs was determined. Uptake into the leaf discs was linear with respect to external concentration from 10^?8 to 10^?3 M. Metabolic inhibitors and uncouplers (DNP, FCCP, CCCP, NaN₃, NaCN, DCMU) decreased uptake 58 to 85 %. Uptake was also sensitive to temperature, with maximum uptake occurring at 23°C. The Q₁₀ for uptake between 13 and 23°C was 1-7. The uptake of all 3 imidazolinones was sensitive to the pH of the uptake solution. Maximum uptake occurred at pH 4. However, there were differences in the rate of uptake among the three herbicides. Imazaquin was absorbed the most rapidly followed by imazethapyr and then imazapyr. These differences in uptake reflected the differences in the lipophilicity of the chemicals at pH 4 and 7. The apparent K_ow of imazaquin, imazethapyr and imazapyr at pH 4 was 7-7, 1-4, and 0-1, respectively, and at pH 7 was 0-04, 0-02, and 0-004, respectively. Based on these results the mechanism of uptake is probably best explained by ion trapping.     

Mechanism of hydantoin ring opening in iprodione in aqueous media

The hydrolysis kinetics of iprodione in alkaline solutions of pH 8.3 to 12 at 25°C have been determined by ultraviolet spectrophotometry. Under these conditions, iprodione leads quantitatively and irreversibly to N-(3,5-dichloroanilinocarbonyl)-N-(isopropylaminocarbonyl)glycine. The reaction is not subject to a general basic catalysis and the rate law takes the form K_obs = K_OH- [OH^?1]. The activation entropy of -77 J mol^?1deg^?1, the value of the kinetic solvent isotope effect k_OH?/k_OD? of 0.79 and the value of 0.60 for the Hammett parameter σ, obtained for the hydrolysis of a series of 3-aryl-N-isopropyl-2,4-dioxoimidazolidine-1-carboxamides are all in agreement with the rate-determining attack by the hydroxyl ion on the carbonyl in the 4-position of the hydantoin ring of the fungicide.     

Host status of cultivated plants to <Emphasis Type="Italic">Meloidogyne hispanica</Emphasis>

The reproduction of a Meloidogyne hispanica isolate from Portugal was evaluated in 63 plant species/cultivars, in pot assays at 25?±?2.0°C, on the basis of root gall index (GI) and reproduction factor (Rf?=?final/initial egg density) at 60 days after inoculation. Cultivars of aubergine, bean, beetroot, broccoli, carnation, corn, cucumber, French garlic, lettuce, melon, onion, parsley, pea, potato, spinach, and tobacco and two of cabbage were susceptible (3?≤?GI?≤?5; 1.15?≤?Rf?≤?262.86). Cabbage cv. Bacalan, cauliflower cv. Temporão and pepper cv. Zafiro R2 were hypersusceptible or poor hosts (Rf??2) and pepper cvs. Aurelio and Solero were resistant (0.0?≤?GI?≤?0.4; 0.00?≤?Rf?≤?0.03). The response of the pepper cultivars and the Mi-1 resistant tomato cv. Rossol was also conducted in pots using two inoculum levels and four temperatures, three growth chamber (25?±?2.7°C, 29.3?±?1.8°C and 33.6?±?1.2°C) and one outdoors (24.4?±?8.2°C). At 24.4?±?8.2°C and 25?±?2.7°C, the reproduction on the resistant tomato was significantly lower compared to the susceptible cv. Easypeel. At all temperatures, resistance was evident for the pepper cultivars, despite the fact they were not found to contain any of the Me1, Me3, Me7 and N genes. The eggs obtained on cv. Aurelio at 33.6?±?1.2°C were used to get a selected resistance breaking isolate of M. hispanica that was able to reproduce on the three pepper cultivars. Our results suggest that the initial M. hispanica isolate is a mixture of virulent and avirulent individuals. The pepper cultivars tested, have potential to reduce M. hispanica populations in agro-ecosystems under certain conditions, but they should be used as a part of an integrated management strategy in order to prevent the development of virulent populations.     

Characterization of residues in soybeans grown in soil treated with 1,3-dichloropropene soil fumigant

The metabolism of cis- and trans-1,3-dichloropropene (1,3-D) was studied in soybean plants grown in soil treated 24 days prior to planting with [U-¹⁴C]E- and Z-1,3-dichloropropene at 380 liters ha^?1. Isolation and identification of the ¹⁴C residue from soybean plants at 84 days (forage) and 176 days (mature) after application showed that no 1,3-dichloropropene or its putative metabolites, 3-chloroallyl alcohol and 3-chloroacrylic acid, could be detected in any of the tissues. The components of the ¹⁴C residue included major plant constituents (i.e. fatty acids, protein, pigments, organic acids, sucrose and other carbohydrates, and lignin).     

Dégradation chimique ou microbiologique des sulfonylurées dans le sol. I. Cas du sulfbméturon méthyle

La Vitesse de transformation du sulfométuron méthyle dans un sol, et en solution au même pH, a été mesurée à différentes temperatures. Aussi bien en solution que dans le sol, la relation d'Arrhénius est bien vérifiée dans la gamme de température étudiée 20°C-75°C. L'énergie d'activation calculée est respectivement de 94 kJ mol^?1 et de 117 kJ mol^?1 dans le sol et en solution. Du fait que la loi d'Arrhénius est vérifiée dans le sol jusqu'à 70°C, un mécanisme de dégradation est proposé: la dégradation chimique. L'analyse des produits formés dans un sol stérile et non stérile a été réalisée a partir du sulfométuron méthyle marqué au ¹⁴C sur le cycle pyrimidine. Dans les deux sols le métabolite principal retrouvé est la 2-amino-4,6-diméthyl-pyrimidine. Aucune différence significative n'est mise en évidence entre le sol sterile et non stérile. Chemical or microbial degradation of sulfonylurea herbicides in soil. I. Sulfometuron methyl The rates of degradation of sulfometuron methyl in a soil and in aqueous solution at the same pH were measured at different temperatures. The Arrhenius relationship was verified between 20°C and 75°C. The calculated activation energy in soil and in solution was 94 kJ mol^?1 and 117 kJ mol^?1, respectively. From the fact that the Arrhenius relationship is followed up to 70°C, it is proposed that the mechanism of degradation in the soil is chemical. Analysis of the metabolites formed in sterile and non-sterile soil was performed using sulfometuron methyl labelled with ¹⁴C in the pyrimidine ring. In both soils the main metabolite isolated was 2-amino-4,6-dimethylpyrimidine. No significant difference has been observed between sterile and non-sterile soils. Chemischer oder mikrobiologischer Abbau von Sulfonylharnstoffen im Boden. I. Sulfometuronmethyl Die Abbaurate von Sulfometuron-methyl wurde in einem Boden und in wäßriger Lösung mit gleichem pH-Wert bei verschiedenen Temperaturen untersucht. Die Gültigkeit der Arrhenius-Gleichung wurde zwischen 20 und 75°C überprüft, mit Aktiviemngsenergien von 94 oder 117 kJ mol^?1 für den Boden bzw. die Lösung. Aus dem linearen Abbau im Boden bis zu 70°C wurde auf chemischen Abbau geschlossen. Bei der Analyse der Abbauprodukte von ¹⁴C-Sulfometuron-methyl (markiert am Pyrimidin-Ring) in sterilisiertem und nicht sterilisiertem Boden wurden keine signifikanten Unterschiede festgestellt und hauptsächlich das 2-Amino-4,6-dimethylpyrimidin gefunden.     

Comparison between the penetration characteristics of methyl bromide and ethanedinitrile through the bark of pine (Pinus radiata D.Don) logs

BACKGROUND

Ethanedinitrile (EDN) is a fumigant being commercialized worldwide as an alternative phytosanitary treatment to methyl bromide (MB) for forest products. The penetration characteristics of MB and EDN were measured through the bark of wooden blocks (100 × 100 × 50 mm) cut from the upper (average bark thickness 5 ± 2 mm) and lower (average bark thickness 25 ± 5 mm) trunk of recently felled pine (Pinus radiata D.Don) trees. Doses of 48 g m⁻³ MB and 50 g m⁻³ EDN were applied to chambers at 10 and 20°C for 10 h.

RESULTS

Penetration of MB was influenced by the interaction between fumigation time and temperature, with concentrations increasing at a higher rate at 20°C compared with at 10°C. After 10 h, an average concentration of 8.05 ± 0.89 g m⁻³ had penetrated the bark of log sections at 20°C, whereas 5.20 ± 0.89 g m⁻³ was measured at 10°C. By contrast, the factors examined in this study did not significantly impact the penetration of EDN. Concentration × time (CT) values for MB under the bark were 35.20 ± 2.30 g h m⁻³ at 10°C and 55.85 ± 9.58 g h m⁻³ at 20°C; whereas for EDN, CT values were 19.50 ± 6.80 g h m⁻³ at 10°C and 19.08 ± 4.10 g h m⁻³ at 20°C.

CONCLUSION

MB can achieve a higher concentration under the bark of log sections during simulated fumigations, but all of the factors examined affected the ability of MB to penetrate the bark of wooden blocks. By comparison, the penetration of EDN through the bark is more consistent than MB under laboratory conditions. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Persistence studies with [14C] 2,4-D in soils previously treated with herbicides and pesticides

The persistence of [¹⁴C] 2,4-D at a rate equivalent to 1 kg/ha was compared under laboratory conditions in samples of heavy clay, sandy loam, and clay loam at 85% of field capacity moisture and 20 ± 1°C which had either received no pre-treatment, or had been pre-treated for 7 days at the 2 μg/g level with the herbicides benzoylprop-ethyl, diclofop-methyl, dinitramine, flamprop-methyl, nitrofen, picloram, tri-allate, trifluralin, and a combination of tri-allate and trifluralin. The breakdown of [¹⁴C] 2,4-D was also studied in the same soils that had similarly received pre-treatments of 2 μg/g of the cereal seed dressing Vitaflo-DB, the insecticide, malathion, and a combination of Vitaflo-DB and malathion. In each soil type, the half-life of the 2,4-D was similar regardless of whether the soil had, or had not, received any pre-treatment, indicating that none of the chemicals investigated adversely affected the soil degradation of 2,4-D.     

Effect of temperature on the toxicity of low concentrations of methyl bromide to diapausing larvae of the warehouse moth Ephestia elutella (Hübner)

The performance of low concentrations of methyl bromide against diapausing larvae of Ephestia elutella at 15 and 25°C was assessed in extended exposure periods. At concentrations of 1.9 mg litre^?1 and below, test batches required higher concentration-time (ct) products for 100% kill at 25°C than at 15°C. The minimum concentration at which the concentration: time relationship still applied was between 1.3 and 1.9 mg litre^?1 at 15°C, whereas at 25°C it was between 2.7 and 4.0 mg litre^?1. For many individuals within each population sample, however, lower concentrations at moderate dosage levels remained lethal. At 25°C, a ct product of about 90 mg litre^?1 h gave between 53 and 77% kill at 6.1, 4.0, 2.7 and 1.9 mg litre^?1. The trends observed suggest that the most tolerant members of the population have an enhanced ability to detoxify methyl bromide at the higher temperature. The implications of the results for the build-up of resistance and for practical control measures are discussed.     

Fate of metsulfuron-methyl in soils in relation to pedo-climatic conditions

The dependence of the behaviour of metsulfuron-methyl on soil pH was confirmed during incubations under controlled laboratory conditions with two French soils used for wheat cropping. The fate of [¹⁴C] residues from [triazine-¹⁴C]metsulfuron-methyl was studied by combining different experimen-tal conditions: soil pH (8·1 and 5·2), temperature (28 and 10°C), soil moisture (90 and 50% of soil water holding capacity) and microbial activity (sterile and non-sterile conditions). Metsulfuron-methyl degradation was mainly influenced by soil pH and temperature. The metsulfuron-methyl half-life varied from five days in the acidic soil to 69 days in the alkaline soil. Under sterile conditions, the half-life increased in alkaline soil to 139 days but was not changed in the acidic soil. Metsulfuron-methyl degradation mainly resulted in the formation of the amino-triazine. In the acidic soil, degradation was characterised by rapid hydrolysis giving two specific unidentified metabolites, not detected during incubations in the alkaline soil. Bound residues formation and metsulfuron-methyl mineralisation were highly correlated. The extent of bound residue formation increased when soil water content decreased and was maximal [48 (±4)% of the applied metsulfuron-methyl after 98 incubation days] in the acidic soil at 50% of the water holding capacity and 28°C. Otherwise, bound residues represented between 13 and 32% of the initial radioactivity. © 1998 SCI     

Grain sorghum response and Palmer amaranth control with postemergence application of fluthiacet-methyl

Palmer amaranth is a problematic weed in grain sorghum production in central United States. Due to limited herbicide options available and ever increasing herbicide-resistant weed species, there is a demand for new mode-of-action herbicides for use in grain sorghum. Fluthiacet-methyl is a relatively new active ingredient that inhibits the enzyme protoporphyrinogen oxidase in target plants. Field studies were conducted at three sites in central United States in 2010 and 2011 to evaluate crop response and Palmer amaranth control with postemergence application of fluthiacet-methyl in grain sorghum. Treatments included fluthiacet-methyl at 4.8 and 7.2 g active ingredient (a.i.) ha^?1 alone and tank-mixed with 2,4-D amine at 260 g acid equivalent (a.e.) ha^?1 or atrazine at 840 g a.i. ha^?1. Carfentrazone at 8.8 g a.i. ha^?1, atrazine at 840 g ha^?1, and a non-treated control were also included. Fluthiacet-methyl treatments caused 9–38% crop injury at 4 ± 1 days after treatment. Tank-mixing atrazine with fluthiacet-methyl seldom affected crop injury, while mixing 2,4-D with fluthiacet-methyl often reduced crop injury. Generally, injury caused by fluthiacet-methyl alone or in combination with atrazine or 2,4-D disappeared within 3 weeks after treatment. Grain yields were reduced in one trial, when 2,4-D mixed with 4.8 or 7.2 g ha^?1 of fluthiacet-methyl caused 18% and 13% plant lodging and 24% and 14% grain yield loss, respectively. Across site-years, fluthiacet-methyl alone at 4.8 or 7.2 g ha^?1 provided 55–95% control of Palmer amaranth. Greater Palmer amaranth control (≥75%) with fluthiacet-methyl alone was achieved when weeds were small or density was low at the time of spraying. Tank-mixing atrazine with fluthiacet-methyl increased Palmer amaranth control and sorghum yields considerably. Tank-mixing 2,4-D with fluthiacet-methyl also increased Palmer amaranth control, but to lesser extent and less consistently than with atrazine. Results indicated that fluthiacet-methyl has potential for use in grain sorghum to combat weeds resistant to acetolactase synthase-inhibitors, triazines, and synthetic auxin herbicides. Tank-mixing atrazine or 2,4-D with fluthiacet-methyl is desirable for effective Palmer amaranth control.