Sodium N-methyldithiocarbamate Research Articles

Effects of rate and application method on the efficacy of metam sodium to reduce clubroot (Plasmodiophora brassicae) of canola

Clubroot, caused by Plasmodiophora brassicae, has become a serious threat to canola (Brassica napus) production in western Canada. Experiments were conducted to evaluate the effect of rate of metam sodium fumigant (dithiocarbamate; sodium N-methyldithiocarbamate; trade name Vapam) and application methods including watering, soil surface covering, and soil incorporation on clubroot of canola. At higher rates (0.4–1.6 mL−1 L soil) metam sodium increased canola seedling emergence and plant health, and reduced root hair infection, gall weight and clubroot severity under greenhouse conditions. Metam sodium application improved subsequent plant growth and reduced clubroot severity, but land preparation and volume of water applied did not affect efficacy. The incorporation of metam sodium into the soil and plastic covering after application improved fumigant efficacy. The study showed that soil fumigation with metam sodium can reduce clubroot severity and improve plant health in the subsequent canola crop.

Gas-Phase Reaction of Methyl Isothiocyanate and Methyl Isocyanate with Hydroxyl Radicals under Static Relative Rate Conditions

Gaseous methyl isothiocyanate (MITC), the principal breakdown product of the soil fumigant metam sodium (sodium N-methyldithiocarbamate), is an inhalation exposure concern to persons living near treated areas. Inhalation exposure also involves gaseous methyl isocyanate (MIC), a highly reactive and toxic transformation product of MITC. In this work, gas-phase hydroxyl (OH) radical reaction rate constants of MITC and MIC have been determined using a static relative rate technique under controlled laboratory conditions. The rate constants obtained are 15.36 × 10(-12) cm(3) molecule(-1) s(-1) for MITC and 3.62 × 10(-12) cm(3) molecule(-1) s(-1) for MIC. The average half-lives of MITC and MIC in the atmosphere are estimated to be 15.7 and 66.5 h, respectively. The molar conversion of MITC to MIC for OH radical reactions is 67% ± 8%, which indicates that MIC is the primary product of the MITC-OH reaction in the gas phase.

Detection and Seasonal Abundance of Sirex nigricornis and Eriotremex formosanus (Hymenoptera: Siricidae) Using Various Lures and Trap Trees in Central Louisiana, U.S.

The recent introduction and spread of the nonnative woodwasp Sirex noctilio F. in North America has generated interest in the ecology of resident Siricidae. In 2 trapping experiments we compared 8 treatments for attractiveness to siricids. Four treatments consisted of traps baited with one of the following lure combinations: 70:30 α-β-pinene alone (Sirex lure); Sirex lure 95% ethanol; Sirex lure ipsenol ipsdienol; Sirex lure 95% ethanol ipsenol ipsdienol. The remaining treatments consisted of blank traps adjacent to standing, chemically debilitated Pinus taeda L. trap trees, created with either sodium N-methyldithiocarbamate (Woodfume®) and dimethyl sulfoxide, or Vanquish® herbicide (dicamba), on 2 separate dates. In a third experiment we compared trap catches among these 2 trap tree treatments and an ethanol lure using traps placed at 2 heights. We collected Sirex nigricornis F. in the fall months, with a peak in midNovember, and Eriotremex formosanus Matsumura in the spring, summer and fall, with a peak in midOctober. We collected no S. noctilio, nor males of any siricid species. The addition of ethanol and/or Ips sp. pheromones to the Sirex lure did not significantly improve collection of any siricids, and all semiochemical treatments were more effective for detecting S. nigricornis than trap trees. Traps positioned low upon dicamba-created P. taeda trap trees were most effective for detecting E. formosanus; however, no progeny emerged from trap trees. We provide detailed phenology and baseline data not previously reported on 2 species of Siricidae in central Louisiana.

Fumigant Treatment of Douglas-Fir Bridge Timbers

Abstract The residual protective effect of sodium n-methyldithiocarbamate (NaMDC) fumigant was investigated in Douglas-fir timbers in a bridge in western Oregon using fungal colonization and levels of methylisothiocyanate (MITC; the primary fungitoxic breakdown product of NaMDC) as the measures of protection. MITC levels were above the presumed protective threshold 7 years after treatment and remained above that level in four of five timbers 12 years after treatment. These results differ from those found in round timbers and suggest that the combination of a protective-treated shell and the sawn surface resulted in a more prolonged protective period against renewed fungal attack. These results illustrate the benefits of NaMDC treatment on bridge timbers.

土壌中におけるカーバム (Sodium-N-methyldithiocarbamate) の殺菌効果

土壌中におけるカーバム (Sodium-N-methyldithiocarbamate) の殺菌効果

Metam Sodium Reduces Viability and Infectivity of Eimeria Oocysts

Metam sodium (MS, sodium N-methyldithiocarbamate) is a widely used soil pesticide. Fumigation or chemical sterilization of poultry litter containing infectious oocysts could be an effective strategy to block the transmission of avian coccidia. In the current study, the effect of MS on the viability and infectivity of ocysts was investigated. The development of isolated, unsporulated oocysts of both Eimeria tenella and Eimeria maxima was inhibited, in a dose-related manner (IC(50) 8 to 14 microg/ml), by exposure to aqueous MS. Most treated oocysts failed to develop beyond early stages of sporulation. To determine the effect of MS on infectivity, isolated oocysts of E. tenella , Eimeria acervulina , and E. maxima were exposed for 24 hr to aqueous concentrations of MS ranging from 0 to 1,000 microg/ml. Treated oocysts were inoculated into chickens, and parameters of coccidiosis infection were compared to chickens inoculated with equal numbers of untreated oocysts. In a dose-related manner, MS significantly reduced the infectivity of oocysts with maximum effect observed at a dose of 300 microg/ml. When a mixture of oocysts containing 3 coccidian species was exposed to 300 microg/ml MS, from 0 to 24 hr, infectivity of oocysts was significantly reduced after a minimum of 12 hr of exposure. Treatment of aqueous slurries of litter samples obtained from commercial poultry houses, with 300 microg/ml MS for 24 hr, prevented the sporulation of eimerian oocysts in the litter samples relative to untreated control samples. The results indicate that MS could be used to reduce coccidial contamination of poultry litter.

Dose Response of Weed Seeds, Plant-Parasitic Nematodes, and Pathogens to Twelve Rates of Metam Sodium in a California Soil

Metam sodium (sodium N-methyl dithiocarbamate, metam-Na) is widely used in agricultural and floricultural production for controlling soilborne plant pathogens, parasitic nematodes, and weeds. It undergoes rapid decomposition to the biocide methyl isothiocyanate (MITC) in moist soils. In this study, the efficacy of 12 concentrations of metam-Na (10 to 2,650 μmol kg-1 soil) to control seeds or tubers of five major weed species, three soilborne pathogens, and one parasitic nematode was evaluated in a sandy loam soil under controlled conditions. Soils were exposed to the fumigant in microcosms for 24 h at 10 and 20°C. Generation and dissipation curves of MITC in soil under controlled conditions showed that MITC concentrations in soils were highest 2 h after metam-Na application and decreased steadily over the 24-h incubation period. After 24 h, remaining MITC concentrations in soil microcosms at 10 and 20°C were 53 and 38% of the original amount applied, respectively, indicating a 20% reduction in MITC dissipation at the lower soil temperature. Logistic dose-response models were used to estimate the effective concentration necessary to reduce soil pest viability by 50 (LC50) or 90 (LC90) percent under both temperatures. Seed of Portulaca oleracea, with LC90 values of ≤1,242 μmol kg-1 soil, was the most sensitive to soil fumigation with metam-Na, followed by Polygonum arenastrum with LC90 values of ≤1,922 μmol kg-1 soil. At 10°C fumigation temperature, metam-Na at the highest dose tested in this study, 2,650 μmol kg-1 soil, was not sufficient to achieve adequate control of Stellaria media and Malva parviflora seed and Cyperus esculentus tubers. Weed control efficacy (average reduction in LC90 values) of metam-Na was between 25 and 60% higher if soils were fumigated at 20°C compared with 10°C, with the exception of M. parviflora. Phytophthora cactorum and Pythium ultimum were more sensitive to soil fumigation with metam-Na (LC90 ≤ 165 μmol kg-1 soil) than Verticillium dahliae (LC90 ≤ 737 μmol kg-1 soil). The nematode Tylenchulus semipenetrans was highly sensitive to soil fumigation with metam-Na (LC90 ≤ 98 μmol kg-1 soil), and the efficacy of control increased by 30% if soil was fumigated at 20°C compared with 10°C. In this sandy loam soil, metam-Na at a concentration of 850 μmol kg-1 reduced the viability of Portulaca oleracea and Polygonum arenastrum seeds, C. esculentus tubers, and all soilborne pathogens and parasitic nematodes tested by 90% at 20°C after 24 h exposure. These results indicate that metam-Na can provide effective pest and disease control at maximum label rate for the commercial formulation, but there was a reduction in efficacy at low temperature.

Chemical Alternatives to Methyl Bromide for Weed Control and Runner Plant Production in Strawberry Nurseries

The phase out of methyl bromide (MB) requires effective alternatives for soil disinfestation, particularly in high-elevation strawberry (Fragaria × ananassa Duch.) nurseries. Methyl bromide alternative fumigants were evaluated over a 3-year period for weed control and runner plant yields at strawberry nurseries in Spain. Two types of field trials were carried out: replicated experiments and commercial-scale field demonstrations. In the replicated experiments, eight fumigant treatments were evaluated each year, including the nonfumigated control and commercial standard methyl bromide plus chloropicrin mixture (MB : Pic) (50 : 50 w/w). Among the treatments evaluated were dazomet, chloropicrin (Pic) alone, metam sodium plus chloropicrin (MS + Pic), 1,3-dichloropropene:chloropicrin (1,3-D : Pic) (61 : 35 w/w), DMDS plus chloropicrin (DMDS + Pic), and propylene oxide. The best alternative fumigant treatments from the replicated experiments were carried forward to the demonstration phase of the project. Treatments such as 1,3-D : Pic (300 kg·ha−1), the combination of metam sodium plus chloropicrin (Pic) (400 to 500 + 150 to 250 kg·ha−1), Pic alone (300 kg·ha−1) as well as dazomet (400 kg·ha−1) controlled weeds at the level of MB : Pic (400 kg·ha−1). Runner plant yields, in soils previously fumigated with alternative fumigants varied, among years, locations, and trial scale, i.e., commercial scale, or small plot. By comparison, runner plant yields in MB : Pic-fumigated soils were consistently high among years, location, and trial scale. Chemical names used are: 1,3-D, 1,3-dichloropropene; MB, methyl bromide; Pic, trichloronitromethane; MS, sodium N-methyldithiocarbamate; DMDS, dimethyl disulphide; dazomet, tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione; PO, propylene oxide

Soil microbial, fungal, and nematode responses to soil fumigation and cover crops under potato production

Sodium N-methyldithiocarbamate (metam sodium) and 1,3 dichloropropene are widely used in potato production for the control of soil-borne pathogens, weeds, and plant parasitic nematodes that reduce crop yield and quality. Soil fumigation with metam sodium has been shown in microcosm studies to significantly reduce soil microbial populations and important soil processes such as C and N mineralization. However, few published data report the impact of metam sodium on microbial populations and activities in potato production systems under field conditions. Fall-planted white mustard (Brassica hirta) and sudangrass (Sorghum sudanense) cover crops may serve as an alternative to soil fumigation. The effect of metam sodium and cover crops was determined on soil microbial populations, soil-borne pathogens (Verticillium dahliae, Pythium spp., and Fusarium spp.), free-living and plant-parasitic nematodes, and C and N mineralization potentials under potato production on five soil types in the Columbia Basin of Eastern Washington. Microbial biomass C was 8–23% greater in cover crop treatments compared to those fumigated with metam sodium among the soil types tested. Replacing fumigation with cover crops did not significantly affect C or N mineralization potentials. Cumulative N mineralized over a 49-day laboratory incubation averaged 18 mg NO3-N kg−1 soil across all soil types and treatments. There was a general trend for N mineralized from fumigated treatments to be lower than cover-cropped treatments. Soil fungal populations and free-living nematode levels were significantly lowered in fumigated field trials compared to cover-cropped treatments. Fumigation among the five soil types significantly reduced Pythium spp. by 97%, Fusarium spp. by 84%, and V. dahliae by 56% compared to the mustard cover crop treatment. The percentage of bacteria and fungi surviving fumigation was greater for fine- than coarse-textured soils, suggesting physical protection of organisms within the soil matrix or a reduced penetration and distribution of the fumigants. This suggests the potential need for a higher rate of fumigant to be used in fine-textured soils to obtain comparable reductions in soil-borne pathogens.

Weed Control in Strawberry Provided by Shank- and Drip-applied Methyl Bromide Alternative Fumigants

The loss of methyl bromide (MB) as a soil fumigant has created the need for new weed management systems for crops such as strawberry (Fragaria ×ananassa Duchesne). Potential alternative chemicals to replace methyl bromide fumigation include 1,3-D, chloropicrin (CP), and metam sodium. Application of emulsified formulations of these fumigants through the drip irrigation system is being tested as an alternative to the standard shank injection method of fumigant application in strawberry production. The goal of this research was to evaluate the weed control efficacy of alternative fumigants applied through the drip irrigation system and by shank injection. The fumigant 1,3-D in a mixture with CP was drip-applied as InLine (60% 1,3-D plus 32% CP) at 236 and 393 L·ha-1 or shank injected as Telone C35 (62% 1,3-D plus 35% CP) at 374 L·ha-1. Chloropicrin (CP EC, 95%) was drip-applied singly at 130 and 200 L·ha-1 or shank injected (CP, 99%) at 317 kg·ha-1. Vapam HL (metam sodium 42%) was drip-applied singly at 420 and 700 L·ha-1. InLine was drip-applied at 236 and 393 L·ha-1, and then 6 d later followed by (fb) drip-applied Vapam HL at 420 and 700 L·ha-1, respectively. CP EC was drip-applied simultaneously with Vapam HL at 130 plus 420 L·ha-1 and as a sequential application at 200 fb 420 L·ha-1, respectively. Results were compared to the commercial standard, MB : CP mixture (67:33) shank-applied at 425 kg·ha-1 and the untreated control. Chloropicrin EC at 200 L·ha-1 and InLine at 236 to 393 L·ha-1 each applied singly controlled weeds as well as MB : CP at 425 kg·ha-1. Application of these fumigants through the drip irrigation systems provided equal or better weed control than equivalent rates applied by shank injection. InLine and CP EC efficacy on little mallow (Malva parviflora L.) or prostrate knotweed (Polygonum aviculare L.) seed buried at the center of the bed did not differ from MB : CP. However, the percentage of weed seed survival at the edge of the bed was often higher in the drip-applied treatments than in the shank-applied treatments, possibly due to the close proximity of the shank-injected fumigant to the edge of the bed. Vapam HL was generally less effective than MB : CP on the native weed population or on weed seed. The use of Vapam HL in combination with InLine or CP EC did not provide additional weed control benefit. Chemical names used: 1,3-dichloropropene (1,3-D); sodium N-methyldithiocarbamate (metam sodium); methyl bromide; trichloro-nitromethane (chloropicrin).

Soil Flooding and Fumigant Alternatives to Methyl Bromide in Tomato and Eggplant Production

Methyl bromide (MeBr) is an important and effective soil fumigant commonly used to control weeds and soilborne pests. Because MeBr has been implicated as a contributor to the depletion of stratospheric ozone, it is scheduled for phaseout by 2005. This study examined nonchemical and chemical practices as alternatives to MeBr. Off-season flooding followed by a series of soil preplant chemical treatments [MeBr with 33% Pic; 1,3-D mixed with 17% (C-17) and 35% (C-35) Pic combined with Peb; and metam-Na combined with 1,3-D and Peb were evaluated on spring tomato (Lycopersicon esculentum Mill.) and eggplant (Solanum melongena) production in northern Florida. Pest control and tomato and eggplant yields were not significantly different between the flooded and non-flooded control plots. The most effective alternatives to MeBr were 1,3-D and Pic mixtures (C-17 and C-35) combined with Peb. Tomato and eggplant yields for these chemicals were statistically equivalent to that of MeBr. Tomato, but not eggplant, yield and nematode control were poor with metam-Na combined with 1,3-D and Peb in comparison to the other fumigant combinations. Chemical names used: 1,3-dichloropropene (1,3-D); trichloronitromethane [chloropicrin (Pic)]; S-propyl butyl(ethyl)thiocarbamate [pebulate (Peb)]; sodium N-methyldithiocarbamate (metam-sodium (metam-Na)].

The soil organisms responsible for the enhanced biodegradation of metham sodium

On a farm near Perth, Western Australia, where metham sodium (sodium N-methyldithiocarbamate) soil fumigant has been extensively used for the past decade, a dramatic case of enhanced biodegradation has been identified. On this soil, the applied dose of metham sodium produced less than half the maximum concentration of the toxin methyl isothiocyanate (MITC) reached in similar, previously untreated soil. Also, the MITC formed was present in the soil for less than 5% of the time of that in the untreated soil. On sterilisation of the affected soil in an autoclave, followed by treatment with metham sodium, the MITC concentration/time relationship was similar to that of the previously untreated soil, confirming that the enhanced degradation was the result of a biological process. Dry heat treatment of the affected soil (100°C, 1 h) did not destroy the microorganisms responsible for enhanced biodegradation, as the soil recovered its degrading ability upon rehydration. This indicated that microorganisms with resistant stages were involved, at least in part, in the biodegradation of MITC. Agar containing MITC as a carbon source was used to isolate bacteria from fresh soil exhibiting enhanced biodegradation. All 18 isolates selected were Gram positive. Morphologically, 11 isolates resembled Rhodococcus spp., 4 isolates resembled Bacillus spp. and 3 were unidentified. Inoculation with these isolates grouped together into soil that had been sterilised by autoclaving resulted in biodegradation of MITC in that soil.

Methyl isothiocyanate volatilization from fields treated with metam-sodium

Emission of methyl isothiocyanate (MITC) from fields treated with metam-sodium (sodium N-methyldithiocarbamate) is a potential environmental and human safety hazard. Concentrations of MITC at three heights above four arable fields were measured following the application of metam-sodium at a rate of 480 litre ha−1 (166 kg AI ha−1). Two of these fields were treated by injection into a center-pivot irrigation system (chemigation), while in the other two fields the fumigant was applied through injection directly into the soil. Generally, higher MITC air concentrations were observed above chemigated than above injected fields. Maximum MITC air concentrations were 11.2 and 7.4 µg m−3 recorded 10 cm above ground 6–8 h following application and the minimum concentrations were 0.7 and 0.2 µg m−3 observed at 200 cm 30–35 h after application above chemigated and injected fields, respectively. The estimated MITC respiratory exposure a worker might encounter during the re-entry period ranged between 1.37 and 0.03 mg day−1 in chemigated fields and between 0.35 and 0.02 mg day−1 in the injected fields. These results suggest that application of the fumigant through injection reduced MITC volatilization losses in comparison with the chemigation method, thus posing a relatively lower risk of exposure to MITC emissions. © 2000 Society of Chemical Industry

A Meta-analysis of Strawberry Yield Response to Preplant Soil Fumigation with Combinations of Methyl Bromide–chloropicrin and Four Alternative Systems

Yield for annual California strawberry (Fragaria ×ananassa Duch.) production systems in soils treated with combinations of methyl bromide–chloropicrin (MB:CP) were compared with four alternative soil treatment systems using meta-analysis. Studies represent 11 production seasons, and were conducted at three distinct locations in California. Fumigation with mixtures of methyl bromide (MB) and chloropicrin (CP) increased yield significantly compared with any and all alternatives lacking MB. In a combined analysis of 45 studies, fumigation with MB:CP compounds increased yield an average of 94.4% (d+ = 2.874 ± 0.098) compared with yields for plants in nonfumigated (NF) soils. Further, the effect of MB:CP fumigation increased over the first three strawberry cultivation cycles: MB:CP–fumigated soils provided a 59.2% (d+ = 2.166 ± 0.146) yield advantage when one cycle of fumigation was omitted, a 100.2% (d+ = 3.000 ± 0.143) advantage when two cycles were omitted, and a 148.4% (d+ = 6.201 ± 0.348) yield advantage when three or more cycles of MB:CP were omitted. In a combined analysis that included 34 studies, soil fumigation with MB:CP conferred a 9.6% (d+ = 0.751 ± 0.087) yield advantage over fumigation with CP alone. Soils treated with MB:CP yielded 6.8% (d+ = 0.437 ± 0.114) more fruit than those treated with very high rates of CP (336–396 kg·ha–1), and 15.4% (d+ = 1.190 ± 0.134) more than soils treated with commercially realistic rates (168–224 kg·ha–1). Similar to the comparison using NF soils, the efficacy of very high rates of CP appeared to diminish over cycles of strawberry cultivation; MB:CP increased yield 2.2% (d+ = 0.043 ± 0.162) in the first CP production cycle, 10.6% (d+ = 0.588 ± 0.174) and 13.7% (d+ = 2.054 ± 0.401) in the following two cycles. Combinations of dichloropropene (DP) and CP were no more effective than were lower rates of CP alone, and MB:CP conferred a 14.4% (d+ = 0.962 ± 0.162) yield advantage over mixtures of DP:CP. Mixtures of MB:CP increased yield 29.8% (d+ = 3.199 ± 0.287) compared with metam sodium (MS). The standardized effect was similar when comparing MB:CP combinations with either MS or NF soils, suggesting little effect of MS on the yield response. Chemical names used: trichloronitromethane (chloropicrin); 1,3-dichloropropene (dichloropropene); sodium N-methyldithiocarbamate (metam sodium).

Efficacy of Sodium Tetrathiocarbonate and Propiconazole in Managing Armillaria Root Rot of Almond on Peach Rootstock.

The efficacy of sodium tetrathiocarbonate (STTC or Enzone 31.8%, a liquid formulation that releases carbon disulfide) and the demethylation inhibiting (DMI) fungicide propiconazole (Alamo 1.1EC) was evaluated for management of Armillaria root rot of almond grown on Lovell peach rootstock. After 12 months, pre-/post-plant STTC (189 liters of 3,850 and 500 mg/liter/3 m2 treatment site, respectively) or tarped pre-plant methyl bromide (Dowfume 98%, 454 g a.i./3 m2) soil fumigation treatments significantly (P < 0.05) reduced the recovery of Armillaria mellea from naturally infected root segments at 0.3 and 1.2 m soil depths, compared with control sites. Tarped methyl bromide treatments eradicated the fungus from infested root segments at both depths; however, nontarped sites significantly reduced the recovery only at the 1.2 m depth. Pre-plant STTC (189 liters of 3,850 mg/liter/3 m2) reduced the recovery of the fungus but was not as effective as the pre-/post-plant STTC treatment. Recovery of the fungus in post-plant treatments with STTC (189 liters of 500 mg/liter/3 m2) was not significantly (P > 0.05) different from control sites. Additionally, mortality of almond tree replants from phytotoxicity was significantly higher in post-plant applications of STTC, compared with the other treatments or with the control trees. A gel formulation of 31.8% STTC (1,800 ml of 318,000 mg of STTC per liter per tree stump) applied in wells that were drilled into tree stumps eradicated the fungus from trunk and primary roots but not secondary or tertiary roots, whereas liquid formulations of STTC and metam-sodium (Vapam - 32.7% sodium N-methyldithiocarbamate) eradicated the fungus from only trunks but not roots. Treatments with STTC (189 liters of 500 mg/liter/3 m2) were not effective in preventing mortality of A. mellea-infected, mature, 7- to 8-year-old almond trees. Propiconazole (Alamo 1.1EC) was shown to be toxic to mycelial growth of A. mellea grown on potato dextrose agar with an EC50 value of 0.15 mg/liter. Therapeutic, passive injections of propiconazole into 7- to 8-year-old almond trees (Lovell peach rootstock) were successful in reducing mortality of infected trees during two growing seasons, compared with infected control trees treated with water.

Fumigant Alternatives to Methyl Bromide for Polyethylene-mulched

Tomato (Lycopersicon esculentum Mill.) was grown to evaluate various chemicals as possible alternatives to methyl bromide soil fumigation. Due to a combination of weeds, nematodes, and soil fungi, the use of a broad-spectrum fumigant has been essential for economical tomato production in Florida. Methyl bromide (MBr) and combinations of MBr with chloropicrin (Pic) are the fumigants of choice for most growers using polyethylene mulch culture. In 1991, MBr was allegedly associated with stratospheric ozone depletion. The U.S. Environmental Protection Agency has since mandated a phaseout of MBr for soil fumigation in the United States by the year 2001. At three locations in Florida, alternative soil fumigants were evaluated, including soil injected 98% MBr—2% Pic at 450 kg·ha-1, 67% MBr—33% Pic (390 kg·ha-1), Pic (390 kg·ha-1), dichloropropene + 17% Pic (1,3-D + Pic) at 327 L·ha-1, and metam-sodium (935 L·ha-1). Also, metam-sodium and tetrathiocarbonate (1870 L·ha-1) were applied by drip irrigation. Dazomet (450 kg·ha-1) was surface applied and soil incorporated. Pebulate (4.5 kg·ha-1) was soil incorporated with some treatments. Pic and 1,3-D + Pic treatments provided good to moderate control of nematodes and soil fungi except in one of the six studies, in which nematode control with 1,3-D was moderate to poor. Nutsedge densities were suppressed by addition of pebulate. Tomato fruit yields with 1,3-D + Pic + pebulate and with Pic + pebulate at the three sites ranged from 85% to 114%, 60% to 95%, and l01% to 119%, respectively, of that obtained with MBr treatments. Pest control and crop yield were lower with treatments other than the above pebulate-containing or MBr-containing treatments. These studies indicate that no one alternative pesticide can provide the consistent broad-spectrum control provided by MBr. Chemical names used: trichloronitromethane (chloropicrin); 1,3-dichloropropene (1,3-D); sodium N-methyldithiocarbamate (metam-sodium); sodium tetrathiocarbonate (tetrathiocarbonate); 3,5-dimethyl-(2H)-tetrahydro-l,3,5-thiadiazine-2-thione (dazomet); S-propyl butyl(ethyl)thiocarbamate (pebulate).

Blockade of ovulation in the rat by the fungicide sodium N-methyldithiocarbamate: Relationship between effects on the luteinizing hormone surge and alterations in hypothalamic catecholamines

Sodium N-methyldithiocarbamate (SMD), also known as metam sodium, is a commonly employed soil fungicide and nematocide. Structurally related dithiocarbamates have been found to decrease norepinephrine (NE) synthesis by suppressing the activity of dopamine-β-hydroxylase. Because brain hypothalamic catecholamine (CA) activity is involved in generating the proestrus afternoon surge in blood luteinizing hormone (LH) which stimulates the final stages of ovulation, this study explored the effect of SMD on this hormonal trigger and its relationship to changes in hypothalamic CAs. Ovariectomized, steroid-primed Long-Evans rats showed a dose-related (25–100 mg/kg, IP) suppression of the surge and a drop in NE when SMD was given at 1100 h, a few h prior to the expected LH rise. The surge effect was reversed by the α-adrenergic agonist clonidine. With cycling rats, a decline with dose (50–300 mg/kg, 1300 h, proestrus) was seen in the percentage of ovulating females, with earlier injections (0900 h) being less effective at the highest dose. At all doses, low circulating levels of LH and prolactin at 1600 h suggested either a blockade in the proestrus surges of each hormone or a displacement in their time of occurence. Anterior and posterior hypothalamic NE fell by 3 h postinjection and was accompanied by a rise in dopamine, while serotonin was unchanged. Although there was a distinct parallel between the alterations in regional CAs and the incidence of ovulation at the high doses of SMD, the relationship did not hold as the dose decreased. A similar dissociation between ovulation and CAs was seen when equimolar doses of SMD or methylisothiocyanate, a principal metabolite, were given by gavage. At the regional level of analysis employed, the data indicate that while IP injections of SMD are able to block the LH surge and ovulation in these rats, the dose-reponse relationship suggests that, along with induced alterations in CA metabolism, an additional factor may be involved in the observed effects.

Simultaneous Determination and Confirmation of Sodium N-Methyldithiocarbamate (Metham SodiumR) and Methyl Isothiocyanate in Water by High Performance Liquid Chromatography with Diode Array Detection

Abstract A high performance liquid chromatographic (HPLC) procedure was developed for determination and confirmation of sodium N-methyldithiocarbamate and methyl isothiocyanate (MITC) present in water. Both analytes are separated on a strong anion exchange column (25 cm × 4.6 mm × 5 μm) with a mobile phase of (45+55, V/V) methanol/buffered water (pH 6.9) containing 10mM hexadecyltrimethyl ammonium bromide (CTAB) and are measured by UV using 242 and 284 nm wavelengths. Diode array spectra were acquired for confirmation. Analyte recoveries were 108% and 114%, respectively when both compounds were present in raw surface water. Linear calibration plots from 5 μg/L to 250 mg/L for MITC and 5 mg/L to 250 mg/L for Metham SodiumR with correlation coefficients of >0.99, were obtained. Precision data and analyte UV/VIS spectra for confirmation are shown for both compounds. The detection limit is 2 μg/L for MITC and 2 mg/L for Metham SodiumR

Replant Management Strategies Influence Early Growth of Apple Trees in a Sand Soil

Abstract Two field experiments were conducted to evaluate the influence of rootstock (seedling, M.26, MM.106), soil fumigation (metam-sodium, methyl bromide), and planting hole substrate (original soil, non-orchard soil, organic mix) on early growth of ‘Granny Smith’ apple trees (Malus domestica Borkh.) in a Quincy sand. Application of soil fumigants in the fall before tree planting the next spring or replacement of the original soil with non-orchard planting hole substrates having greater water-holding capacity and nutrient status significantly improved tree growth. Combination of fumigation and soil replacement had a synergistic positive effect on tree growth. The size-controlling characteristics of the rootstocks were evident in the non-orchard soil and organic mix treatments, but not when the trees were planted in the original orchard soil. Chemical name used: sodium N-methyldithiocarbamate (metam-sodium).

Fumigant Protection of Untreated Douglas-Fir Posts

Sodium n-methyldithiocarbamate, chloropicrin, and methylisothiocyanate were tested for their ability to protect untreated Douglas-fir posts from decay and insect attack. Removal of increment cores for culturing and bioassays indicated that fumigants slowed, but did not prevent, Basidiomycete colonization. All posts contained surface decay after 4 years and termite attack after 10 years of exposure in ground contact. Pilodyn tests indicated that mechanical properties of all posts also declined, regardless of treatment, although MIT-treated posts declined least. The results suggest that fumigant treatment cannot completely protect non-pressure-treated Douglas-fir from decay but may be useful for low-stress applications, such as for fence posts. Fumigant treatment is not a substitute for proper pressure treatment where service conditions are severe. © 1988, Walter de Gruyter. All rights reserved.