Residual free methyl bromide in fumigated commodities

The extent to which methyl bromide was retained by fumigated material after treatment was followed in laboratory studies on a range of commodities exposed to the vapour at atmospheric pressure. Amounts of methyl bromide, recovered by solvent extraction and determined using gas-liquid chromatography, were related to the temperature, moisture content and manner of post-treatment storage. Immediately after exposure, the initial amount of free methyl bromide present was more dependent on the gas concentration used than on the time of exposure. Under the experimental conditions of exposure, the residual free methyl bromide in all commodities fumigated at 25°, except cocoa beans and groundnuts, fell to below 1 ppm within a few days when they were held at that temperature, whether spread in thin layers on trays or kept sealed in glass bottles. At lower temperatures, the rate of loss was slower, small amounts of methyl bromide being extracted from several commodities one month after treatment. The disappearance of fumigant from wheat and sultanas was more rapid from samples with higher moisture contents. A mathematical treatment of the data is presented, to assist in prediction of the behaviour of residual fumigant under storage conditions before processing. It is concluded that the risk of ingestion of harmful quantities of free methyl bromide by the consumer is small and that the occasions when relatively high residues might occur can be predicted.     

Pesticide residues in foodstuffs in England and Wales. Part I: Inorganic bromide ion in lettuce grown in soil fumigated with bromomethane

Surveys of lettuce, produced commercially in England and Wales, were carried out during the years 1977–82 to determine residues of inorganic bromide ion, following soil sterilisation with bromomethane. Lettuce grown on unfumigated soil contained less than 10 mg bromide ion kg⁻¹, while most lettuce grown on bromomethane-fumigated soil were found to contain higher levels of bromide ion, with a proportion in excess of 1000 mg kg⁻¹. The accumulation of bromide ion appeared to be related to the interval between soil fumigation and planting, and also to the frequency of bromomethane application to the soil. A limited amount of data is presented on the levels of bromide ion in imported lettuce.     

Influence of methyl bromide soil fumigation method on fungicidal efficacy and bromide residues

Highest inorganic bromine residues (30 ppm) were found when soil was fumigated with liquid methyl bromide (MB) introduced by conventional means into evaporating dishes. With preheated (vaporized) MB or injection of MB/chloropicrin (CP) mixtures, bromide concentrations were reduced by 50%. They were uniform throughout the soil (0 to 60 cm) except after MB/CP injection, when larger residues were found in the 30-60 cm layer. Leaching with 2000 m^p3/ha (20 cm) of water always reduced bromide content to 7.5 and 10 ppm at the 0-30 and 30-60 cm depth, respectively. Organic amendments to soils substantially increased bromide levels up to 118 ppm, most of which was found in the upper soil layers; two teachings with 2000 m^p3 /ha water were required to return the soils to their normal state.Sclerotium rolfsii andFusarium oxysporum f. sp.dianthi cultures buried in soil were eliminated from the upper 30 cm with MB applied either conventionally or preheated. At 50 cm, 500 kg/ha of the preheated gas was superior to 1000 kg/ha of the cold gas. All MB fumigations suppressed carnation flower yields compared with CP alone but were superior to no treatment. After leaching, MB-fumigated soils yielded the highest number of flowers.     

Replacing methyl bromide in annual strawberry production with glucosinolate-containing green manure crops

The use of biocidal green manure crops is an agronomic technique for amending soil with fresh organic matter containing volatile compounds active in controlling some soil-borne pests and diseases. Two new selections of the Brassicaceae family were cultivated, incorporated before planting strawberries and tested as an alternative to fumigation with methyl bromide. Two biocidal green manure crops (Brassica juncea L sel ISCI20, Eruca sativa Mill cv Nemat) containing glucosinolate-myrosinase systems, a conventional green manure (barley), untreated soil and a fumigated control were evaluated during two seasons. The effect of these soil management systems on subsequent strawberry performance was evaluated by monitoring yield and plant growth parameters. In both years, biocidal plant green manure treatments led to a fruit yield lower than with methyl bromide, but higher than with conventional green manure or untreated soil. These results confirm the good prospects for biocidal green manures, not only as an environmentally friendly alternative to methyl bromide in conventional agriculture, but also in organic agriculture as an alternative to conventional green manure crops.     

Pesticide residues in foodstuffs in England and Wales. Part II: Inorganic bromide ion in cucumber,tomato and self-blanching celery grown in soil fumigated with bromomethane,and the ‘natural’ bromide ion content in a range of fresh fruit and vegetables

Surveys of inorganic bromide ion residues in tomatoes, cucumbers and selfblanching celery, commercially produced in England following soil sterilisation with bromomethane, have been carried out since 1979. The mean bromide ion level in 29 late-season cucumber samples was approximately 28 mg kg⁻¹ and ranged up to 109 mg kg⁻¹. Analysis of 242 tomato samples gave estimated mean bromide ion levels per plant ranging from 6 to 187 mg kg⁻¹ in fruit picked throughout the season from seven holdings, on six of which bromomethane had been used fairly recently prior to planting. A statistically significant fall in bromide levels over the growing season was shown on four of the sites. In 38 samples of self-blanching celery, the mean bromide ion level was 104 mg kg⁻¹ even though the mean interval between fumigation and planting was in excess of 1 year. Retail surveillance indicated that a large number of crops are likely to have bromide ion levels below 10mg kg⁻¹.     

Effect of soil physical factors on methyl iodide and methyl bromide

Production and importation of methyl bromide is scheduled to be banned by 2001. Methyl iodide was evaluated as a possible replacement soil fumigant. The effects of soil moisture, temperature, soil texture and fumigation time on the efficacy of methyl iodide for the control of two common weeds, Abutilon theophrasti and Lolium multiflorum, were characterized and compared with those of methyl bromide. The optimal soil moisture for methyl iodide to kill both weed species in sandy soils was 14% water content (w/w). Greater efficacy was obtained when the temperature during fumigation was above 20°C. Compared to methyl bromide, the efficacy of methyl iodide was more consistent in different soils. Time to 100% mortality of weeds was 24 h for methyl iodide fumigation and 36 h for methyl bromide when 200 μM of fumigant was used. On a molar basis methyl iodide was consistently more effective than methyl bromide across the range of environmental factors tested. In terms of application technology and spectrum of activity, methyl bromide can be directly replaced by methyl iodide. © 1998 SCI     

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).     

Aminopyralid soil residues affect rotational vegetable crops in Florida

BACKGROUND: Bahiagrass (Paspalum notatum Flueggé) is a poor host of several soilborne pests of vegetable crops; therefore vegetable crops are commonly grown in a rotation with bahiagrass pastures in Florida. The herbicide aminopyralid provides foliar and soil residual weed control and increases forage production in bahiagrass pastures; however, the soil residual activity of aminopyralid makes carryover injury likely in subsequent sensitive vegetable crops. Field research was conducted to determine the sensitivity of five vegetable crops to soil residues of aminopyralid. RESULTS: At an aminopyralid soil concentration of 0.2 µg kg^?1 (the limit of quantitation for aminopyralid in this research), crop injury ratings were 48% (bell pepper), 67% (eggplant), 71% (tomato), 3% (muskmelon) and 3% (watermelon), and fruit yield losses (relative to the untreated control) at that concentration were 61, 64, 95, 8 and 14% in those respective crops. CONCLUSIONS: The crops included in this research were negatively affected by aminopyralid at soil concentrations less than the limit of quantitation (0.2 µg kg^?1). Therefore, it was concluded that a field bioassay must be used to determine whether carryover injury will occur when these crops are planted on a site where aminopyralid has been previously applied. Copyright © 2011 Society of Chemical Industry     

溴甲烷土壤消毒替代技术研究进展

概述了溴甲烷替代品的新进展。在土壤消毒方面,新的进展有化学替代品:氯化苦胶囊、氯化苦乳剂、氯化苦+噻唑磷混用、C₂N₂、氰铵化钙、异硫氰酸烯丙酯、异硫氰酸甲酯、1,3—二氯丙烯和氯化苦混剂、碘甲烷、环氧丙烷、叠氮化合物、硫酰氟等。在使用技术上,采用化学灌溉和注射施药技术进一步提高药剂分布的均匀性。在非化学替代技术上,生物熏蒸和有机质补充正受到重视。减少溴甲烷的技术正在快速地发展。     

Fonofos residues in an organic soil and vegetable crops following treatment of the soil with the insecticide

Fonofos (O-ethyl S-phenyl ethylphosphonodithioate) was applied to an organic soil as band treatment at the rates of 1.12 and 2.24 kg/ha. The persistence of the insecticide and its translocation into onions and two rotation crops (lettuces and carrots) was studied under field conditions. Proportionally more residues persisted in the soil from the higher rate of application. In autumn, 4 months after soil treatment, about 40-48 % of the initially recovered levels of fonofos remained in soil. However, the amount of fonofos present at the harvest time, during the second growing season was only 16–26% of the insecticide concentration found in spring. Onions harvested 4 months after application of fonofos had no detectable residue (> 0.005 mg/kg) whereas lettuces and carrots grown in the following year contained fonofos in various amounts. At the lower rate of application the insecticide residues in lettuces and carrots were < 0.005 and 0.025 mg/kg, respectively, and those from the higher application rate were 0.012 and 0.036 mg/kg. About 72–80% of the residue could be removed by peeling the carrots. No residue of the oxygen analogue, O-ethyl S-phenyl ethylphos-phonothioate (I) was detected in any soil or crop samples.     

高效液相色谱-串联质谱法快速检测马铃薯与土壤中氟醚菌酰胺残留

建立了采用QuEChERS为样品前处理方法的高效液相色谱-串联质谱（HPLC-MS/MS）快速检测马铃薯和土壤中氟醚菌酰胺残留的分析方法。样品经乙腈提取,PSA、C18吸附剂净化,电喷雾电离、正离子模式采集,多反应监测模式检测,基质匹配标准品外标法定量。结果表明:在0.002~1 mg/L范围内,氟醚菌酰胺在马铃薯等基质中的质量浓度与对应的峰面积间呈良好的线性关系,其相关系数均大于0.999 9。在 0.005~0.5 mg/kg添加水平下,氟醚菌酰胺在马铃薯、马铃薯植株和土壤中的日内平均回收率为81%~98%,日内相对标准偏差（RSD）为2.2%~13%（n = 5）;日间平均回收率为75%~106%,日间RSD为0.6%~11%（n = 15）。氟醚菌酰胺在马铃薯等基质中的定量限（LOQ）（S/N=10）均为0.001mg/kg。该方法简便、快速、准确,可用于马铃薯中氟醚菌酰胺的残留检测。     

Analysis of metsulfuron‐methyl residues in wheat field soil: a comparison of HPLC and bioassay techniques

BACKGROUND: Metsulfuron‐methyl is a low‐application‐rate sulfonylurea herbicide that is widely used to control broad‐leaved weeds in wheat. Owing to its persistent nature, its residues may be present at phytotoxic levels for the next crop in rotation. Therefore, a comparative evaluation of HPLC and bioassay techniques was made for the analysis of this herbicide in wheat field soil. RESULTS: Metsulfuron‐methyl was applied to wheat crop at different rates (4, 8 and 12 AI ha^?1) at 28 days after sowing as a post‐emergence application, and the soil was analysed for metsulfuron‐methyl residues by HPLC and lentil seed bioassay techniques. The bioassay was found to be the more sensitive technique. At the recommended rate of application, 4 g AI ha^?1, the bioassay technique could detect the residue up to 30 days in surface soil, while, with HPLC, residues were not detectable on the 15th day. The half‐lives of metsulfuron‐methyl by HPLC and bioassay were calculated as 6.3–7.8 and 17.5 days respectively. Under field conditions, residues of metsulfuron‐methyl were also detected in subsurface soil by the bioassay technique at trace levels, but were not detected by the solvent extraction/HPLC method. CONCLUSION: Lentil seed bioassay is a more sensitive technique than HPLC. Traces of residues detected in subsurface soil indicated the mobility of metsulfuron‐methyl into lower layers. Copyright © 2009 Society of Chemical Industry     

Sulcotrione soil persistence and mobility in summer maize and winter wheat crops

Sulcotrione soil persistence in spring maize ( Zea mays L.) crops grown on a sandy loam soil was greater at pH 5·5 and 6·0 (soil half-life T _1/2≈58 days) than at pH 7·1 ( T _1/2 = 44 days). Sulcotrione was also applied as recommended on a summer maize crop at the five- to six-leaf growth stage, grown on a sandy loam soil. Sulcotrione soil half-life was 44 days, and the herbicide remained mainly in the 0- to 5-cm surface soil layer during the cropping period, in spite of the high water solubility and the heavy rains at the end of August; lower sulcotrione concentrations (10–18% of the total during the 2-month period after sulcotrione application) were detected in the 5- to 10-cm surface soil layer. The herbicide was applied pre-emergence to winter wheat ( Triticum aestivum L.) at four sites that differed in their soil texture and composition: loamy sand, sandy loam, loam and clay loam. Persistence was greater in the soils containing more organic matter. In soils having similar organic matter contents, persistence was lower in the soil containing more sand relative to loam and clay. During the winter crops, sulcotrione moved down to the 10- to 15-cm soil layer, in spite of the fact that the rains were lower in winter than in summer. Sulcotrione most generally was not detected in the 15–20 cm soil layer of the maize and winter wheat crops.     

Determination of phosphine residues in fumigated cereals and other foodstuffs

An improved method for the determination of phosphine residues in a range of stored foodstuffs with a limit of detection better than 0.1, μg kg^?1 is described. The method has been used to obtain data on the amount of phosphine which remains in these commodities after treatment at typical dosage levels and on its persistence during storage. Results show that in cereal grains and nuts residues fall quickly to below internationally recommended levels although trace amounts of phosphine could be detected several months after treatment in all commodities examined.     

溴甲烷在番茄土壤消毒中替代技术研究

采用保护地内划分小区实验方法，在番茄载培过程中，研究了代替溴甲烷的其它3种消毒技术，结果表明，生物熏蒸，人工基质和阿维菌素对防治根结线虫都有不同的效果，增产幅度分别为18．9％，14．05％，19．0％，同时嗅甲烷土壤消毒增产22．06％。从直接经济效益看，阿维菌素＞生物熏蒸＞溴甲烷＞人工基质。     

Determination of methyl bromide residues in stored foods using automated headspace gas chromatography

An automated gas chromatographic headspace method capable of detecting methyl bromide (MB) down to 0.01 mg kg^?1 has been developed and evaluated. The method is suitable for analysing cereals, nuts, seeds and dried fruit. Commodities are extracted with solvent and MB present is derivatised to methyl iodide (MI) which is determined by automated headspace gas chromatography. Results from the method described are compared with those using an established solvent extraction method and show good quantitative agreement. The analytical conditions recommended are likely to be suitable for examination of other commodities for MB residues.     

Non-destructive method for estimating methyl bromide residues in apples during aeration following fumigation

A method is presented for estimating the persistence and concentration of residual free methyl bromide (MB) present in apples during the aeration period following fumigation. The method is based on determining the rate of decline in concentration of methyl bromide in the exhaust air stream during aeration. The rate was shown to follow two consecutive pseudo-first-order decay curves. The first component of the curve resulted primarily from removal of MB from the free air space in the chamber, and the second component resulted from the desorption of MB from the apples. Estimates of the concentration of MB residue in apples were obtained from the regression parameters for the second decay curve. The technique gave good estimates of the residue concentration over a wide range of fumigation conditions and ventilation rates, and may be useful for determining the duration of aeration period required to achieve a proposed residue tolerance of 0.2 mg kg ^?1 methyl bromide.