Monosodium Methanearsonate Research Articles

Dissipation of monosodium methane arsonate (MSMA) on peanuts.

Monosodium methane arsonate (MSMA), the salt of methylarsonic acid (MAA), is a herbicide commonly used to control weeds along roadsides, in cotton, in turf, and on noncrop sites. In recent years questions have arisen regarding the source and nature of arsenic residues in raw agricultural commodities relative to misuse, inadvertent exposure, or rotational crop residues. Field experiments were conducted to determine the fate of MSMA that is applied to peanut foliage. Persistence, dissipation, recovery, and detection of MAA from leaf rinsate were characterized as well as resulting total arsenic and MAA concentrations in peanut kernels. MSMA was applied to peanut foliage at 105, 210, 315, and 420 g of active ingredient (ai)/ha. Peanut leaves were sampled before and after irrigation events over the next 7 days. Peanuts were harvested at maturity and analyzed for MAA and total arsenic. A confined rotational crop experiment was conducted to determine the potential for MAA residues in soil to be taken up by peanuts in fields rotated from cotton that was treated with MSMA. MAA was not detected in any peanut samples from the rotational crop experiment, even when peanuts were planted only 30 days after MSMA application to the soil at 2.24 kg of ai/ha. Field experiments showed that MSMA recovery from leaves with an aqueous rinse declined quickly but was not greatly affected by irrigation. However, quantifiable amounts of MAA were present 1 week after application and after two irrigation events, and MAA and total arsenic were measured in mature peanut kernels from all plots that received MSMA. MAA was not detected in untreated checks. Total arsenic was below the limit of quantification in untreated controls.

Effectiveness of Ammonium Thiosulfate to Enhance Weed Control and Reduce Cotton (Gossypium hirsutum) Injury1

Field experiments were conducted in 1997 and 1998 at the Prattville Experiment Field in Prattville, AL and the Wiregrass Substation in Headland, AL to determine if ammonium thiosulfate (ATS) additions to monosodium methanearsonate (MSMA) affects weed control, reduces MSMA-induced cotton injury, lessens the fruiting and maturity delay on cotton caused by MSMA, and lessens MSMA-induced yield reductions in cotton. Treatments were applied before cotton was at the pinhead square stage and the weeds were 5 cm tall. Weeds evaluated were sicklepod, morningglory species, yellow nutsedge, and Texas panicum. ATS additions to MSMA occasionally enhanced control of all weeds 5 to 20%. However, the addition of ATS did not reduce crop injury caused by MSMA, the effects of MSMA on cotton maturity, or yield reductions caused by MSMA.Nomenclature: MSMA, monosodium methanearsonate; morningglory species, Ipomoea spp. #3 IPOZZ; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; Texas panicum, Panicum texanum Buckl. # PANTE; yellow nutsedge, Cyperus esculentus L. # CYPES; cotton, Gossypium hirsutum L.Abbreviations: ATS, ammonium thiosulfate; DAT, days after treatment; POST, postemergence.

The effects of toxicants on planktonic systems: an integrated approach using the analysis of size distributions

We measured size distributions in model wetlands to detect stressor effects at the community level. Two experiments investigated the individual and combined effects of methyl mercury, chlorpyrifos, atrazine, monosodium methane arsonate, and UV-B light on the system. The statistical analysis of the metric using size distributions, which integrated information about organisms 0.2–4750 µm in size, detected effects in the planktonic community. Effects were found in both experiments, but only when methyl mercury was present in the treatment structure, indicating that system level effects are most likely with broad spectrum or persistent toxicants. Methyl mercury negatively affected most size classes measured in both experiments. A methyl mercury × chlorpyrifos interaction was detected which shifted the size distribution to larger organisms more than expected, but the interaction effect was much smaller than the effect of methyl mercury alone.

Modeling Evaluation of Alternative Management Practices and Reclaimed Water for Turfgrass Systems

AbstractThe use of reclaimed water for turfgrass irrigation is being implemented to conserve potable water supplies. Reclaimed water coupled with alternative management strategies may reduce offsite loadings of fertilizers and pesticides. The Environmental Policy Integrated Climate (EPIC) water quality model was used to evaluate alternative management practices and reclaimed water for a southern turfgrass system. One green and fairway were modeled for a 65‐yr period of climatic record with four treatments. Specifically, the treatments were normal water normal management (NWNM), normal water reduced management (NWRM), reclaimed water normal management (RWNM), and reclaimed water reduced management (RWRM). Surface and subsurface nitrate (NO3‐N), fenamiphos (ethyl 3‐methyl‐4‐(methylthio)phenyl (1‐methylethyl)phosphoramidate), and MSMA (monosodium methanearsonate) losses were evaluated. Significant differences were predicted in NO3‐N runoff and leachate losses from green management. Mean annual NO3‐N losses from runoff were 2.85 kg ha−1 (NWNM) and 2.05 kg ha−1 (RWRM). Significant reductions in mean annual surface and subsurface NO3‐N losses from fairway conditions were simulated when comparing NWNM (5.11 kg ha−1 surface; 1.68 kg ha−1 subsurface) to RWRM (2.69 kg ha−1 surface; 0.90 kg ha−1 subsurface). The cited differences in NO3‐N losses in runoff and leachate from green and fairway conditions were attributed primarily to irrigation strategies and excess rainfall. Predicted average annual pesticide recovery in runoff and leachate was <0.01% of applied and no significant differences were predicted with respect to treatments. This modeling strategy provides valuable insight into the relative efficacy of implementing reduced management practices for turfgrass systems.

Purple Nutsedge Control by Halosulfuron or Imazaquin/MSMA in Turfgrass in the Tropics

ABSTRACT Field and greenhouse experiments were conducted to determine the extent of purple nutsedge (Cyperus rotundus L.) control in bermudagrass (Cynodon spp.) turf by halosulfuron (methyl 5- [[(4, 6-dimethoxy-2-pyriiTUdinyl)-amino]carbonylaminosulfonyl]-3-chloro-l-H-pyrazole-4-carboxylate) or imazaquin (2-[4,5-dihydro-4-methyl-4-(l-methyIethyl)-5-oxo-lH-imidazol-2-yl]-3-quinolinecarboxylic acid)/MSMA (monosodium methanearsonate), and to determine the extent of purple nutsedge regrowth from basal bulbs after foliar treatment with these herbicides. Excellent initial control (> 80%) of emerged shoots of purple nutsedge occurred with halosulfuron or imazaquin + MSMA. However, purple nutsedge shoots emerged within 3 or 4 weeks after all treatments, and nutsedge shoot density increased with time. With a rapid increase in purple nutsedge shoot density, the extent of control deteriorated rapidly, even after two applications of halosulfuron. Both halosulfuron at 70 g ha−1 and imazaquin at 0.42 kg ha−1 + MSMA at ...

Photosynthetic Performance of MSMA-Resistant and -Susceptible Mississippi Biotypes of Common Cocklebur

Common cocklebur biotypes resistant to monosodium methanearsonate (MSMA) have been reported in South Carolina, Mississippi, and other locations. The resistance at the whole plant level in Mississippi biotypes was found to be low under growth chamber and greenhouse conditions. The CO 2 exchange rate (CER), as measured by infrared gas analysis of both biotypes, was lowered by MSMA application at 0.5 kg ai ha −1; however, inhibition of carbon assimilation was more rapid and of greater magnitude in the susceptible (S) biotype than the resistant (R) biotype. MSMA affected C i/ C a (the ratio of intercellular CO 2 concentration to the external CO 2 level) of the S biotype more than the R biotype and increased stomatal conductance to water vapor at 48 hr after treatment. There were no rapid effects of MSMA on variable chlorophyll fluorescence in either biotype, indicating that MSMA had no direct effect on photosynthetic electron transport. Furthermore, later reductions in variable fluorescence were not pronounced in either biotype. These data indicate that, at an early stage during the development of herbicide injury, MSMA affects photosynthetic carbon fixation in the S biotype more than in the R biotype.

In vitro cultured cocklebur (Xanthium strumarium L.) responses to dimercaptopropanesulfonic acid and monosodium methanearsonate

Monosodium methanearsonate (MSMA) is an effective herbicide used for the control of Xanthium strumarium (cocklebur), a serious weed problem in cotton production. Recently, MSMA-resistant cocklebur was reported, which reduced MSMA effectiveness in the cocklebur control strategy. The mode of action of MSMA may involve the reduction of the pentavalent arsenic in MSMA to a trivalent form, which may then form a complex with sulfhydryl-containing enzymes. Dimercaptopro-panesulfonic acid (DMPS) chelates trivalent arsenic, resulting in a nontoxic complex. The objective of this study was to determine the effect of DMPS and MSMA on the growth of in vitro grown cocklebur shoot and callus tissues. Lateral and terminal shoots were grown on basal Murashige and Skoog medium containing 6.25 mg L−1 (0.0428 mm) MSMA alone and with various concentrations of DMPS. Callus was cultured on basal callus medium also containing 6.25 mg L−1 MSMA alone and an equimolar concentration of DMPS. Shoot injury symptoms, dry root weight, and fresh weight of callus were recorded. Susceptible cocklebur shoots showed severe discoloration and death when treated with MSMA. Resistant shoots and cultured shoot tips were not adversely affected. DMPS alone did not inhibit growth of these tissues. Callus induced from susceptible tissue was inhibited by MSMA and DMPS alone. In all combinations of DMPS and MSMA tested, DMPS did not counteract the MSMA response. Thus, the pentavalent form of arsenic in MSMA apparently is not reduced to the trivalent form by the plant and hence is not involved in the mechanism of action

Uptake and Translocation of [14C]MSMA in Cotton and MSMA-Resistant and -Susceptible Cocklebur

Common cocklebur (Xanthium strumarium L.) is a competitive weed which interferes with cotton (Gossypium hirsutum L.) production throughout the southeastern United States. In South Carolina, an organic arsenical-resistant cocklebur biotype has been identified. Absorption and translocation studies were conducted comparing monosodium methanearsonate (MSMA)-resistant (R) and -susceptible (S)-cocklebur with tolerant cotton using [14C]MSMA. Radioactivity was distributed throughout all plants and average recovery from plants after 1, 3, and 5 days was 98, 70, and 85%, respectively. Greatest concentrations of 14C activity were located in the treated leaf, with both acropetal and basipetal translocation occurring. There were no significant differences in radioactivity recovered from the three plant types. Cocklebur absorbed more MSMA than did cotton; most 14C activity was removed from the treated cotton leaf in the first water rinse. Cotton cuticle appears to play a role in the MSMA tolerance mechanism. No significant 14C root exudations or 14CO2 evolution from intact plants was detected.

Chronic effects of arsenic on american red crayfish,Procambarus clarkii, exposed to monosodium methanearsonate (MSMA) herbicide

Bioaccumulative and biomagnifying effects of arsenic on crayfish have been reported. However, no work has been done on the chronic effects of this heavy metal on crayfish populations. There is a great concern for MSMA (Monosodium Methanearsonate) herbicide in the vicinity of natural waters due to its high water solubility and bioaccumulative potential. American red crayfish (Procambarus clarkii) account for 98% of the annual crayfish harvest in North America. Those pesticides which have greater water solubility (i.e. MSMA) than other less soluble compounds may cause higher mortalities of aquatic organisms, or cause adverse chronic effects if the non-target animals are sublethally exposed. This work was conducted in the laboratory to assess the possible chronic effects of arsenic on crayfish.

Arsenic uptake and depuration by red crayfish,Procambarus clarkii, exposed to various concentrations of monosodium methanearsonate (MSMA) herbicide

Like many other heavy metals, arsenic is known to accumulate in the tissues of aquatic organisms including crayfish. One of the earliest reports on red crayfish, Procambarus clarkii, reported the bioaccumulation factor (BF) ratios for radioactive sodium methanearsonate to range from 80-480. Other heavy metals, i.e., Cr, Cd, Pb and Hg have also been reported to accumulate experimentally in P. clarkii tissues. This study was conducted to evaluate in the laboratory the bio-accumulative potential of As by the American red crayfish, Procambarus clarkii, which is abundant in Louisiana; and also to assess the level of arsenic present in the tissues of fieldcollected individuals. Total revenues from the sales of this crayfish exceeds $143 million annually.

Toxicity of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and monosodium methanearsonate (msma), individually and in a mixture, to channel catfish (Ictalurus punctatus) and fathead minnows (pimephales promelas)

The toxicity of technical-grade dinoseb, technical monosodium methanearsonate (MSMA), several formulations of each and a mixture of the two were tested using channel catfish (Ictalurus punctatus Rafinesque) and fathead minnows (Pimephales promelas Rafinesque) under standard conditions at 12°C in soft, reconstituted water. The 96-h LC50s for technical dinoseb were 0.058 mg/L for channel catfish and 0.088 mg/L for fathead minnows. Differences among Vertac General®, Vertac Selective®, Premerge 3®, Gebutox® and technical dinoseb did not affect dinoseb toxicity to either fish species. The 96-h LC50s for technical MSMA were 2,390 mg/L for channel catfish and 1,210 mg/L for fathead minnows. Formulation had a measurable effect on MSMA toxicity, with the Daconate® and Daconate 6® formulations nearly an order of magnitude more toxic than technical MSMA and Bueno 6® to both fish species. The mixture or joint toxicity of technical dinoseb and technical MSMA was greater than additive (synergistic), with additive toxicity indices for channel catfish and fathead minnows of 0.51 and 5.78, respectively.

Impact and Role of Monosodium Methanearsonate on Attack and Progeny Production by the Douglas-Fir Beetle (Coleoptera: Scolytidae) in Lethal Trap Trees

Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, trees located in interior British Columbia were baited with frontalin and treated with monosodium methanearsonate (MSMA) on two dates. The first treatment was 2 wk before initial Douglas-fir beetle, Dendroctonus Pseudotsugae Hopkins, flight, and the second coincided with flight. Each application was subjected to three felling regimes (2 and 4 wk, and unfelled) after treatment, as were the controls. MSMA significantly reduced the number of Douglas-fir beetle progeny in all cases but was most effective (greatest attacks, 80% reduction in progeny) in trees treated at the time of initial beetle flight and felled 4 wk later. The unfelled trap trees were least effective (fewest attacks, greatest survival). Samples of phloem and xylem were subjected to arsenic compound (speciation) analysis which identified significant concentrations of inorganic arsenic (arsenate plus arsenite), monomethylarsonic acid (MMAA), and cacodylic acid (DMAA) in treated and untreated trees. The control tree contained mainly inorganic arsenic, but the presence of MMAA and DMAA was consistent with in situ biomethylation. Treatment with MSMA resulted in much higher levels of all arsenicals, with concentrations generally decreasing with height and radially from the phloem to the heartwood boundary. Inorganic arsenic appears to be translocated differently than MSMA, but the elevated levels of inorganic arsenic compounds in the treated tree can be attributed to an impurity in the commercial herbicide. Water content was not correlated with distribution of arsenic. The role of arsenic in the development of lethal trap trees is considered in terms of the translocation of the herbicide, its subsequent chemical fate, and the toxicities of the various arsenic compounds identified in the treated tree. These data strongly suggest that arsenic has a direct insecticidal impact on bark beetle survival.

Distribution of Arsenic in Lodgepole Pines Treated with MSMA

Abstract Fifteen mature lodgepole pines, Pinus contorta var. latifolia Engelmann, were treated with either 1/8-, ¼- or ½-strength monosodium methanearsonate (MSMA) applied to axe-frills around the base of the bole. Using X-ray fluorescence spectroscopy, we determined the arsenic concentration in the phloem, sapwood, and foliage of MSMA-treated and control trees. The highest accumulation of arsenic was in the phloem, near the point of application, and in the foliage. Residual arsenic concentration in the tissues of treated trees averaged <5 ppm above 2 m for all treatment strengths, a concentration probably too low to kill attacking bark beetles or their brood. In addition, the levels of MSMA in the bole tissues of treated trees is well below the 10% safety limit for sawmills stated by the British Columbia Workman's Compensation Board Industrial Health and Safety Regulations. West. J. Appl. For. 3(2):37-40, April 1988.

Distribution of Arsenic in MSMA-Treated Lodgepole Pines Infested by the Mountain Pine Beetle, Dendroctonus ponderosae (Coleoptera: Scolytidae), and Its Relationship to Beetle Mortality

The LC50 of MSMA (monosodium methanearsonate) for first- and second-instar mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins, mining for 4 d in ground phloem tissue impregnated with methane arsonic acid (CH3AsO3H2), the pure form of arsenic in MSMA, was 102 ppm. Application of MSMA 3 wk after attack to axe-frills (cuts) near the root collar of five lodgepole pines, Pinus contorta var. latifolia Engelmann, resulted in high accumulations of arsenic in phloem and sapwood near the point of application and in foliage 11 wk later. MPB taken from bolts cut from MSMA-treated trees 1 m above the axe-frill were all dead. There was a strong relationship between amounts of arsenic in MPB and those in phloem tissue up to 2 m. At sampling points above 2 m on treated trees, arsenic residues in phloem and sapwood were, on average, not significantly different from those occurring naturally in tissues of lodgepole pine. Enough arsenic could have passed through the tissues to kill or inhibit the brood MPB within the trees, but MPB mortality was probably due to an interaction of many factors including moisture deficit and fungal invasion of the host tree.

Oral and dermal toxicity of MSMA to New Zealand white rabbits, Oryctalagus cuniculus.

The 24 day LD/sub 50/ of monosodium methanearsonate (MSMA) for New Zealand white rabbits was estimated to be 102 mg MSMA/kg body weight. The average size of the rabbit dermal irritant patch tests was 1.0, indicating that MSMA is a mild irritant to intact skin. Relatively little work has been done on the toxicity of organic arsenicals, especially the herbicide monosodium methanearsonate (MSMA). The EPA review reported a dermal study carried out on 6 adult male rabbits. The clipped skin areas of the rabbits were exposed to doses of MSMA for a 24 hours period. The animals were observed for a period of 2 weeks for signs of toxicity following the exposure. The dermal LD/sub 50/ value was found to be between 2 and 4 g/kg.

A rapid, multisample technique for detection of trace elements in trees by energy-dispersive X-ray fluorescence spectroscopy

A new method is presented for studying the distribution of trace elements in trees. A tree core is removed, sectioned into very thin slices (≤400 μm), and analyzed directly using X-ray fluorescence spectroscopy. The technique offers a number of advantages, including minimal sample preparation time, elimination of contamination or leaching, and rapid simplified data analysis. Analysis of 10 or more samples per annual ring is possible. Application of the technique in two studies (first, using trees as indicators of airborne pollutants and second, analyzing pesticide residues in trees) is described. In the first study there were significant correlations between seasonal airborne pollution levels and the levels of lead and zinc detected in the phloem tissue of red alder, Alnusrubra Bong. In the other study, the technique was used to analyze arsenic content in lodgepole pines, Pinuscontorta var. latifolia Englemann, treated with monosodium methanearsonate. Vertical arsenic profiles in treated trees indicated accumulations of arsenic near the site of injection at the base of the bole and in the foliage. Differential radial uptake was also apparent.

Some effects of multiple, sublethal doses of monosodium methanearsonate (MSMA) herbicide on hematology, growth, and reproduction of laboratory mice.

Monosodium Methanearsonate (MSMA) is an organic aresenical herbicide used as a selective herbicide for the postemergence control of crabgrass, Dallisgrass and other weedy grasses in turf and for the control of Johnsongrass, nutsedge, watergrass, sandbur, cocklebur, pigweed and grasses in cotton and noncrop areas. The mode of action by which MSMA and similar organic arsonates kill plants seems to be related to a disturbance of phosphorus metabolism (Committee on Medical and Biologic Effects of Environmental Pollutants 1977).

Residues from Organic Arsenical Herbicides in Chemically Thinned Forests

AbstractConifers in four Pacific Northwest locations and forest types were stem‐injected with the organic arsenicals cacodylic acid and monosodium methanearsonate (MSMA), herbicides used for forest thinning and insect control. Concentrations and locations of As residues in tree stems, twigs, foliage, and in litter and soil were determined. Within each forest type, spring treatment led to somewhat higher concentrations in crowns than did fall application; differences were larger with cacodylic acid than with MSMA. Most residue concentrations were in the range of 20 to 60 mg As/kg (dry‐weight basis). Trees killed 5 yr earlier showed As concentrations of 122 to 670 mg/kg in the phloem just above the injection sites, 10.9 to 25.0 mg/kg in the xylem, and 34.7 to 77.8 mg/kg in upper lateral twigs and terminal leader shoots. Residues in litter were lowest (5–9 mg/kg) in Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] stands and highest (27–46 mg/kg) in lodgepole pine (Pinus contorta Engelm.) stands. Surface soil concentrations below the litter traps increased 0 to 3.7 mg As/kg over native soil concentrations of 1 to 7 mg/kg. Most observations were within the range of naturally occurring As in these sites. Persons using fuel from treated stands probably would not receive measurable exposure to toxic forms of As. Residues in fuelwood would be minimized if wood at the point of injection and bark on the lower stem were excluded from the fuel. Bark removal is made easy by injecting arsenicals in the fall.

Arsenic levels in blood, urine, and hair of workers applying monosodium methanearsonate (MSMA).

Uptake and excretion of total arsenic from monosodium methanearsonate (MSMA) in workers who applied the herbicide was followed during the spraying season. Urine, blood, and hair samples were collected and air samples were taken from the workers' breathing zone. Arsenic concentrations in air samples ranged from 0.001-1.086 micrograms/m3. Blood and urine arsenic values ranged from 0.0-0.2 mg/L and 0.002-1.725 mg/L, respectively. The geometric mean arsenic concentration in urine increased during the week but returned to base levels on weekends. Hair arsenic concentrations ranged from 0.02-358.0 mg/kg, increased during the spraying season, and returned to pre-season levels once herbicide application ceased. Three workers had higher than normal pre-exposure hair values. However, only one of the three workers had consistently above normal values throughout the study period.

Comparative toxicity of six test chemicals to lettuce using two root elongation test methods

Lettuce (Lactuca sativa L., cv buttercrunch) was used to evaluate and compare the results from two different root elongation phytotoxicity test methods with the same six test substances. Seeds were either germinated in the dark on an inclined filter paper substrate with one end immersed in test solution or germinated in 0.1 strength nutrient solution with a 16 hr light period in a glass bulb mixed and aerated with compressed air. Sodium fluoride, monosodium methanearsonate and monuron reduced lettuce root length at similar concentrations for both methods, while cadmium chloride and 2,4-D root inhibition occurred at concentrations approximately one order of magnitude smaller in the solution culture method than in the substrate method. Two orders of magnitude difference were observed between the two methods for silver nitrate. The results indicate that the solution method is at least as sensitive for all the chemicals tested and much more sensitive for some.