Fumigant Emissions Research Articles

Determining breakthrough of the soil fumigant chloropicrin from 120 mg XAD-4 sorbent tubes

The emission to the atmosphere of soil fumigants such as chloropicrin represents a potentially important human exposure pathway. Commonly, determining the air concentration of fumigants is carried out by pumping air through sorbent tubes which chemically retain the fumigant. In order to obtain an accurate measurement, it is essential that the fumigant does not break through the sorbent tubes, since this would result in an underestimation. Using a simple apparatus, we tested the potential for chloropicrin breakthrough from 120 mg XAD-4 sorbent tubes. The effects of chloropicrin loading (0.33 and 3.3 mg) and air flow rate (50 and 1000 mL min −1) on the transport of chloropicrin through six XAD-4 tubes (connected in series) were examined over time periods ranging from 1 to 360 min. The higher flow rate led to rapid and high breakthrough of the chloropicrin, especially at the longer time periods. At 360 min, all six tubes together retained only 46–54% (depending on initial loading) of the added chloropicrin. At the lower flow rate, essentially all of the added chloropicrin was always retained on the first two tubes. The effect of flow rate was greater than that of initial chloropicrin loading and sampling time. It is concluded that when 120 mg XAD-4 tubes are used in soil fumigant emission studies, it should be at low flow rates only and always with at least one back-up tube.

Evaluation of Fumigation and Surface Seal Methods on Fumigant Emissions in an Orchard Replant Field

Soil fumigation is an important management practice for controlling soil pests and enabling successful replanting of orchards. Reducing emissions is required to minimize the possible worker and bystander risk and the contribution of fumigants to the atmosphere as volatile organic compounds that lead to the formation of ground-level ozone. A field trial was conducted in a peach orchard replant field to investigate the effects of fumigation method (shank-injection vs. subsurface drip-application treatments) and surface treatments (water applications and plastic tarps) on emissions of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) from shank-injection of Telone C-35 and drip application of InLine. Treatments included control (no water or soil surface treatment); standard high-density polyethylene (HDPE) tarp, virtually impermeable film (VIF) tarp, and pre-irrigation, all over shank injection; and HDPE tarp over and irrigation with micro-sprinklers before and after the drip application. The highest 1,3-D and CP emission losses over a 2-wk monitoring period were from the control (36% 1,3-D and 30% CP) and HDPE tarp (43% 1,3-D and 17% CP) over shank injection. The pre-irrigation 4 d before fumigation and VIF tarp over shank injection had similar total emission losses (19% 1,3-D and 8-9% CP). The HDPE tarp and irrigations over subsurface drip-application treatments resulted in similar and the lowest emission losses (12-13% 1,3-D, and 2-3% CP). Lower fumigant concentrations in the soil-gas phase were observed with drip-application than in the shank-injection treatments; however, all treatments provided 100% kill to citrus nematodes in bags buried from 30 to 90 cm depth. Pre-irrigation and drip application seem to be effective to minimize emissions of 1,3-D and CP.

Thiosulfate and Manure Amendment with Water Application and Tarp on 1,3-Dichloropropene Emission Reductions

Reducing fumigant emissions is required for minimizing bystander risk and environmental impact. Effective and economic field management methods including commonly used surface sealing technique and soil amendments are needed for achieving emission reductions. This research determined the effectiveness of ammonium thiosulfate (ATS) and composted manure amendments to surface soil in combination with water application or high density polyethylene (HDPE) tarp on reducing emissions of 1,3-D from soil columns. Surface treatments included an untreated control, water seal (single water application at time of fumigant injection), ATS amendments at 1:1 and 2:1 molar ratio of ATS:fumigant, composted steer manure at 3.5 kg m(-2), and HDPE tarp over 1:1 ATS or the manure amendment. Cumulative 1,3-D emission loss over two weeks was greatest for the control (52% of applied). The HDPE tarp over ATS and manure treatments had the lowest 1,3-D emissions at 24 and 16%, respectively. Treatments with ATS or manure alone reduced 1,3-D emissions (29-39%) more effectively than water seal (43%) and further benefit was gained with the addition of HDPE tarp. Amendment of surface soil with organic materials shows greater potential in minimizing fumigant emissions than with chemicals with the need for a better understanding of the organic-fumigant reaction mechanism.

Effect of Drip Application of Ammonium Thiosulfate on Fumigant Degradation in Soil Columns

Low permeability tarps can effectively minimize fumigant emissions while improving fumigation efficacy by retaining fumigants under the tarp. However, when planting holes are cut through the tarps, high-concentration fumigants may be released and result in environmental and worker safety hazards. In a 11-day column study, we explored the effect of drip irrigation application of ammonium thiosulfate (ATS) on 1,3-dichloropropene (1,3-D) and chloropicrin (CP) degradation in soil. Decrease of 1,3-D and CP concentrations in soil-gas phase followed a three-parameter logistic equation for all treatments. It was slowest in the control with a half-life ( t 1/2) of 86.0 h for 1,3-D and of 16.3 h for CP and most rapid when ATS was applied at 4:1 ATS/fumigant molar ratio with a half-life of 9.5 h for 1,3-D and of 5.5 h for CP. Our results indicate that applying ATS via the drip-irrigation systems to soil can accelerate fumigant degradation in soil and thus reduce emissions. This technical solution may be applicable in raised-bed strawberry production where drip-application of fumigants under tarps has become common.

Measuring Flux of Soil Fumigants Using the Aerodynamic and Dynamic Flux Chamber Methods

Methods for measuring and estimating flux density of soil fumigants under field conditions are important for the purpose of providing inputs to air dispersion models and for comparing the effects of management practices on emission reduction. The objective of this study was to measure the flux of 1,3-dichloropropene (1,3-D) and chloropicrin at a site in Georgia (GA) using the aerodynamic method and the dynamic flux chamber (FC) method. A secondary objective was to compare the effects of high density polyethylene (HDPE), and virtually impermeable film (VIF) tarps on fumigant flux at a site in Florida (FL). Chloropicrin and 1,3-D were applied by surface drip application of In-Line soil fumigant on vegetable beds covered by low density polyethylene (LDPE), HDPE, or VIF. The surface drip fumigation using In-Line and LDPE tarp employed in this study resulted in volatilization of 26.5% of applied 1,3-D and 11.2% of the applied chloropicrin at the GA site, as determined using the aerodynamic method. Estimates of mass loss obtained from dynamic FCs were 23.6% for 1,3-D and 18.0% for chloropicrin at the GA site. Flux chamber trials at the FL site indicate significant additional reduction in flux density, and cumulative mass loss when VIF tarp is used. This study supports the use of dynamic FCs as a valuable tool for estimating gas flux density from agricultural soils, and evaluating best management practices for reducing fumigant emissions to the atmosphere.

Surface Seals Reduce 1,3‐Dichloropropene and Chloropicrin Emissions in Field Tests

Reducing emissions is essential for minimizing the impact of soil fumigation on the environment. Water application to the soil surface (or water seal) has been demonstrated to reduce 1,3-dichloropropene (1,3-D) emissions in soil column tests. This study determined the effectiveness of water application to reduce emissions of 1,3-D and chloropicrin (CP) in comparison to other surface seals under field conditions. In a small-plot field trial on a Hanford sandy loam soil (coarse-loamy, mixed, superactive, nonacid, thermic Typic Xerorthents) in the San Joaquin Valley, CA. Telone C35 (61% 1,3-D and 35% CP) was shank-applied at a depth of 46 cm at a rate of 610 kg ha-1. Soil surface seal treatments included control (no tarp and no water application), standard high density polyethylene (HDPE) tarp over dry and pre-irrigated soil, virtually impermeable film (VIF) tarp, initial water application by sprinklers immediately following fumigation, and intermittent water applications after fumigation. The atmospheric emissions and gas-phase distribution of fumigants in soil profile were monitored for 9 d. Among the surface seals, VIF and HDPE tarp over dry soil resulted in the lowest and the highest total emission losses, respectively. Intermittent water applications reduced 1,3-D and CP emissions significantly more than HDPE tarp alone. The initial water application also reduced emission peak and delayed emission time. Pre-irrigated soil plus HDPE tarp reduced fumigant emissions similarly as the intermittent water applications and also yielded the highest surface soil temperature, which may improve overall soil pest control.

Permeation of soil fumigants through agricultural plastic films

Plastic films are used in soil fumigation to control fumigant emission into the atmosphere. In previous studies it was shown that the plastic films are permeable to fumigant vapors. Virtually impermeable films (VIF) have been developed to reduce such emission and to increase the efficacy of pest control. A rapid, accurate, sensitive and simple method to measure the permeability of plastic films to soil fumigants that was developed in the present study is described in this paper. The method uses a static, closed system in which the tested film is fixed between two cells. The fumigant is sampled by a solid-phase microextraction method and measured quantitatively by gas chromatography. The method was used to assess the permeability of two plastic films — a low-density polyethylene film (LDPE) and a VIF — to commercial soil fumigants formulated individually or in mixtures. All the tested fumigants permeated through the commonly used LDPE film, in the following descending order of permeability: methyl isothiocyanate (MITC), methyl bromide (MBr), 1,3-dichloropropene (1,3-D; Telone), chloropicrin (CP). The VIF was impermeable to all the tested fumigants except MITC, the permeation of which was reduced by 40%. The permeation of some fumigants through LDPE films was influenced by the formulation used. The permeation of CP was increased when it was combined with MBr in Bromopic. With Telopic, a mixture of 1,3-D and CP, the permeation of 1,3-D through LDPE film was 62% greater than that of Telone, whereas that of CP was not affected. The permeation rates of both MBr and CP were 25–30% greater when they were formulated as a mixture in Bromopic than when they were formulated individually. The formulation of fumigants as mixtures of two components did not affect their permeability through VIF. This study showed that differences in the suitability of plastic films for soil fumigation can be measured easily in a laboratory. It also showed that the VIP was more effective than LDPE in reducing losses of fumigant to the atmosphere, thus allowing more efficient use of fumigants to manage soilborne pests. The presented method helps us to choose the most adequate film for optimizing fumigation efficacy, and reducing costs and environmental risks.

Using Surface Water Application to Reduce 1,3‐Dichloropropene Emission from Soil Fumigation

High emissions from soil fumigants increase the risk of detrimental impact on workers, bystanders, and the environment, and jeopardize future availability of fumigants. Efficient and cost-effective approaches to minimize emissions are needed. This study evaluated the potential of surface water application (or water seal) to reduce 1,3-dichloropropene (1,3-D) emissions from soil (Hanford sandy loam) columns. Treatments included dry soil (control), initial water application (8 mm of water just before fumigant application), initial plus a second water application (2.6 mm) at 12 h, initial plus two water applications (2.6 mm each time) at 12 and 24 h, standard high density polyethylene (HDPE) tarp, initial water application plus HDPE tarp, and virtually impermeable film (VIF) tarp. Emissions from the soil surface and distribution of 1,3-D in the soil-gas phase were monitored for 2 wk. Each water application abruptly reduced 1,3-D emission flux, which rebounded over a few hours. Peak emission rates were substantially reduced, but total emission reduction was small. Total fumigant emission was 51% of applied for the control, 46% for initial water application only, and 41% for the three intermittent water applications with the remaining water treatment intermediate. The HDPE tarp alone resulted in 45% emission, while initial water application plus HDPE tarp resulted in 38% emission. The most effective soil surface treatment was VIF tarp (10% emission). Surface water application can be as effective, and less expensive than, standard HDPE tarp. Frequent water application is required to substantially reduce emissions.

Construction of a reactive surface barrier to reduce fumigant 1,3‐dichloropropene emissions

Halogenated fumigants have been used extensively in production agriculture to control soilborne pests. These types of pesticides are highly volatile and are prone to affect air quality and imperil public health. In the present study, a chemical tarp approach, termed a reactive surface barrier (RSB), was developed to reduce the emission of fumigant 1,3-dichloropropene (1,3-D) from the soil surface. The agrochemicals thiourea and allylthiourea were tested as active reagents for the construction of a RSB, where these soil amendments react with 1,3-D to form nonvolatile isothiuronium ions at the soil surface and, thereby, impede fumigant emission into the atmosphere. The feasibility of the method largely depends on the reactivity of 1,3-D and the RSB agrochemicals in soil as well as on the mobility, persistence, and toxicity of the transformation products. Therefore, the reaction kinetics and transformation mechanism of 1,3-D by thiourea and allylthiourea were studied comprehensively in aqueous solution and soil. A catalytic process occurring at the surface of soil colloids facilitated the reaction between 1,3-D and thiourea in amended soils. The rate of 1,3-D transformation in thiourea-amended soil increased with decreasing soil moisture or increasing thiourea amendment level. In a field trial, a thiourea RSB reduced cumulative 1,3-D emissions by more than 80% relative to that in bare soil surface. The present results clearly indicate that this chemical remediation technology has great potential to control the emissions of volatile halogenated organic contaminants and to mitigate atmospheric pollution.

Effect of Application Variables on Emissions and Distribution of Fumigants Applied via Subsurface Drip Irrigation

Soil fumigation is useful for controlling soil-borne pests and diseases in high-cash-value crops. Fumigants are highly volatile, and approaches to reduce atmospheric emissions are required to protect human and environmental health. Application of fumigants through drip irrigation has been proposed as a means to decrease fumigant emissions, improve fumigant distribution in soil, and minimize worker exposure. These experiments were conducted to investigate the effect of the configuration of the drip system on the volatilization and distribution of the fumigants 1,3-dichloropropene (1,3-D), propargyl bromide (PrBr), and methyl isothiocyanate (MITC) in bedded systems. Results indicated that changing the drip emitter spacing and using multiple drip lines in each bed had little effect on the emissions and distribution of any fumigant. Increasing the depth of application from 15 to 30 cm reduced volatilization of MITC by approximately 20 to >90%; emissions were reduced due to a decrease in the flux from the bed top, and deeper injection did not change the amount of fumigant volatilized from the bed side slope and furrow. Increasing the application depth resulted in a slight decrease in the rate of fumigant dissipation in soil, indicating the potential for some improvement in pest-control efficacy with deeper application.

Effect of surface tarp on emissions and distribution of drip-applied fumigants.

Soil fumigants are used to control a wide variety of soil-borne pests in high-cash-value crops. Application of soil fumigants through drip irrigation systems is receiving increasing attention as a method to improve the uniformity of fumigant application. Little information is available on the emissions and soil distribution of fumigants following subsurface drip application, or the effect of plastic tarp on fumigant emissions in these systems. In these experiments, the fumigant compounds 1,3-dichloropropene (1,3-D), Vapam (a methyl isothiocyanate (MITC) precursor), and propargyl bromide (PrBr) were applied to soil beds via drip irrigation at 15 cm depth. Beds were tarped with either standard 1-mil high-density polyethylene (HDPE) or a virtually impermeable film (VIF), leaving the furrows bare. Cumulative emissions of 1,3-D, MITC, and PrBr in these tarped bedded systems was very low, amounting to <10% of the applied mass. These experiments were conducted in the winter months, with average air temperatures of 12-15 degrees C. Cumulative emissions of MITC and 1,3-D from a sandy loam field soil were decreased by > or =80% by tarping the bed with VIF rather than HDPE. A large fraction of the 1,3-D and PrBr flux was from the untarped furrows in VIF-tarped plots, indicating that inhibiting volatilization from the furrow will be important in further reducing emissions in these systems. Monitoring the fumigant distribution in soil indicated that tarping the bed with VIF resulted in a more effective containment of fumigant vapors compared to use of a HDPE tarp.

Monte Carlo-based dispersion modeling of off-gassing releases from the fumigant metam-sodium for determining distances to exposure endpoints

Fumigants, such as metam-sodium, can help control pests in the soil and improve the quality and yields for a wide range of crops. Enhanced control of field loss, or off-gassing, to the atmosphere is an important means of promoting fumigant efficacy and sound environmental management of fumigants. Metam-sodium has been used for over 40 years and is one of the most widely used fumigants in the United States. This paper describes a modeling method, the fumigant emissions modeling system (FEMS), which was developed to promote more realistic assessment of downwind concentrations in the vicinity of an applied field. Two models of the US Environmental Protection Agency, i.e., the industrial source complex short-term (ISCST3) model and the toxic modeling system short-term (TOXST) model are used, in conjunction with a pre-processing program, PCRAMMET, and the FEMS programming code to provide a Monte Carlo treatment for all key model inputs. Start times for applications are triggered on a Monte Carlo basis consistent with the annual application frequency. Typically, 1000–10,000 years of applications are simulated, outputting data to display average exceedances per year of selected concentration endpoints as a function of distance from the edge of the treatment zone. A sensitivity analysis is displayed for key meteorological variables, showing uncertainty in emission rates to be a significant input parameter. Some comparisons also are made between ambient concentrations and modeled personal and indoor exposures, showing perspective on the benefits of the indoor environment to buffer peak concentrations.

Remediation of methyl iodide in aqueous solution and soils amended with thiourea.

Methyl iodide (MeI) is considered a very promising fumigant alternative to methyl bromide (MeBr) for controlling soil-borne pests. Because atmospheric emission of highly volatile fumigants contributes to air pollution, feasible strategies to reduce emissions are urgently needed. In this study, thiourea (a nitrification inhibitor) was shown to accelerate the degradation of MeI in soil and water. In aqueous solution, the reaction between MeI and thiourea was independent of pH, although the rate of MeI hydrolysis increased in alkaline solution. Substantial increases in the rate of MeI dissipation were observed in thiourea-amended soils. Transformation of MeI by thiourea in aqueous solution was by a single chemical reaction process, while MeI degradation in thiourea-amended soil apparently involved a catalytic mechanism. The electron delocalization between the thiourea molecule and the surfaces of soil particles is energetically favorable and would increase the nucleophilic reactivity of the thiono group toward MeI, resulting in an enhancement of the dissipation rate. The soil half-life for MeI was reduced from >300 h for unamended soils to only a few hours in soil or sand amended with thiourea at a 2:1 molar ratio (thiourea:MeI). The MeI transformation rate in thiourea-amended soil increased with increasing soil temperature and decreasing soil moisture. Therefore, spraying thiourea on the soil surface to form a "reactive surface barrier" may be an effective and innovative strategy for controlling fumigant emissions to the atmosphere and for improving environmental protection.

Accelerated degradation of methyl iodide by agrochemicals.

The fumigant methyl iodide (MeI, iodomethane) is considered a promising alternative to methyl bromide (MeBr) for soil-borne pest control in high-cash-value crops. However, the high vapor pressure of MeI results in emissions of a significant proportion of the applied mass into the ambient air, and this may lead to pollution of the environment. Integrating the application of certain agrochemicals with soil fumigation provides a novel approach to reduce excessive fumigant emissions. This study investigated the potential for several agrochemicals that are commonly used in farming operations, including fertilizers and nitrification inhibitors, to transform MeI in aqueous solution. The pseudo-first-order hydrolysis half-life (t(1/2)) of MeI was approximately 108 d, while the transformation of MeI in aqueous solutions containing selected agrochemicals was more rapid, with t(1/2) < 100 d (t(1/2) < 0.5 d in some solutions containing nitrification inhibitors). The influence of these agrochemicals on the rate of MeI degradation in soil was also determined. Adsorption to soil apparently reduced the availability of some nitrification inhibitors in the soil aqueous phase and lowered the degradation rate in soil. In contrast, addition of the nitrification inhibitors thiourea and allylthiourea to soil significantly accelerated the degradation of MeI, possibly due to soil surface catalysis. The t(1/2) of MeI was <20 h in thiourea- and allylthiourea-amended soil, considerably less than that in unamended soil (t(1/2) > 300 h).

Accelerated Degradation of Methyl Isothiocyanate in Soil

Methyl isothiocyanate (MITC, CH3NCS) is the primary breakdown product of metam-sodium, and a potential replacement fumigant pesticide for methyl bromide. Methyl isothiocyanate is toxic and has a high potential for volatilization, therefore, minimizing its atmospheric emission is of the utmost importance. One method to reduce fumigant emissions is to enhance their degradation by incorporating organic amendments into the soil surface. In this study we determined the combined effect of temperature and chicken manure application rate on the degradation of MITC. The degradation of MITC was significantly accelerated by both increasing temperature and amendment rate. Differences between sterile and nonsterile degradation kinetics in unamended and organically amended soil indicate that MITC degradation is equally controlled by chemical and biological processes. The amelioration of soil with organic amendments should be further considered when designing fumigation practices that allow for reduced emissions.

The Practical Realities of Alternatives to Methyl Bromide: Concluding Remarks

HomePhytopathology®Vol. 92, No. 12The Practical Realities of Alternatives to Methyl Bromide: Concluding Remarks PreviousNext Symposium OPENOpen Access licenseThe Practical Realities of Alternatives to Methyl Bromide: Concluding RemarksJ. W. NolingJ. W. NolingCorresponding author: J. W. Noling: E-mail address: E-mail Address: jwn@mail.ifas.ufl.eduSearch for more papers by this authorAffiliationsAuthors and Affiliations J. W. Noling Published Online:22 Feb 2007https://doi.org/10.1094/PHYTO.2002.92.12.1373AboutSectionsPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat DetailsFiguresLiterature CitedRelated Vol. 92, No. 12 December 2002SubscribeISSN:0031-949Xe-ISSN:1943-7684 Metrics Article History Issue Date: 25 Jan 2008Published: 22 Feb 2007Accepted: 23 Jul 2002 Pages: 1373-1375 Information© 2002 The American Phytopathological SocietyPDF downloadCited byThe role of fungal volatile organic compounds (FVOCs) in biological control17 June 2021 | Türkiye Biyolojik Mücadele DergisiVolatile fatty acids from whey volatilome as potential soil fumigants to control Meloidogyne incognitaCrop Protection, Vol. 143Volatile emissions of watercress ( Nasturtium officinale ) leaves and passion fruit ( Passiflora edulis ) seeds against Meloidogyne incognita20 November 2019 | Pest Management Science, Vol. 76, No. 4Toxicities of 4,5-Dihydroisoxazoles Against Root-Knot Nematodes and in Silico Studies of Their Modes of Action7 January 2020 | Journal of Agricultural and Food Chemistry, Vol. 68, No. 2Integrated Nematode Management in Protected Cultivation21 March 2020Volatile organic molecules from Fusarium oxysporum strain 21 with nematicidal activity against Meloidogyne incognitaCrop Protection, Vol. 106Volatile molecules of Fusarium oxysporum strain 21 are retained in water and control Meloidogyne incognitaBiological Control, Vol. 112Glucosinolate and Isothiocyanate Production for Weed Control in Plasticulture Production System25 April 2017Nematicidal activity of allyl bromide and dibromo(nitro)methane under laboratory conditions8 April 2015 | Pest Management Science, Vol. 72, No. 1Glucosinolate and Isothiocyanate Production for Weed Control in Plasticulture Production System11 May 2016In vitro assessment of the effects of Brassica juncea and Raphanus sativus leaf and root extracts on the viability of Globodera pallida encysted eggsNematology, Vol. 17, No. 5Comparisons of Soil Surface Sealing Methods to Reduce Fumigant Emission Loss1 September 2011 | Journal of Environmental Quality, Vol. 40, No. 5Impact of Spatial Heterogeneity Within Spermosphere and Rhizosphere Environments on Performance of Bacterial Biological Control Agents3 March 2011Active Solarization as a Nonchemical Alternative to Soil Fumigation for Controlling Pests1 January 2011 | Soil Science Society of America Journal, Vol. 75, No. 1Selection of genetically diverse Trichoderma spp. isolates for suppression of Phytophthora capsici on bell pepperCanadian Journal of Microbiology, Vol. 56, No. 10Managing Nematodes Without Methyl BromideAnnual Review of Phytopathology, Vol. 48, No. 1A Nylon Membrane Bag Assay for Determination of the Effect of Chemicals on Soilborne Plant Pathogens in SoilYoujian Lin, Zhenli He, Erin N. Rosskopf, Kenneth L. Conn, Charles A. Powell, and George Lazarovits8 January 2010 | Plant Disease, Vol. 94, No. 2Fungicides and other Chemical Approaches for use in Plant Disease ControlEvaluating Brassica species as an alternative control measure for root-knot nematode (M. incognita) in Georgia vegetable plasticultureCrop Protection, Vol. 26, No. 9Solarização do solo em casa-de-vegetação e campo para o controle de Rhizoctonia solani AG-4Summa Phytopathologica, Vol. 33, No. 3Comparison of Muscodor albus Volatiles with a Biorational Mixture for Control of Seedling Diseases of Sugar Beet and Root-Knot Nematode on TomatoE. Grimme, N. K. Zidack, R. A. Sikora, G. A. Strobel, and B. J. Jacobsen16 February 2007 | Plant Disease, Vol. 91, No. 2Surface Seals Reduce 1,3-Dichloropropene and Chloropicrin Emissions in Field Tests1 January 2007 | Journal of Environmental Quality, Vol. 36, No. 1Comparison of AMF and PGPR inoculants for the suppression of Verticillium wilt of strawberry (Fragaria×ananassa cv. Selva)Applied Soil Ecology, Vol. 32, No. 3Alternatives to Methyl Bromide: A Florida PerspectiveErin N. Rosskopf, Daniel O. Chellemi, Nancy Kokalis-Burelle, and Gregory T. Church27 July 2018 | Plant Health Progress, Vol. 6, No. 1D EVELOPMENT OF A LTERNATIVE S TRATEGIES FOR M ANAGEMENT OF S OILBORNE P ATHOGENS C URRENTLY C ONTROLLED WITH M ETHYL B ROMIDEAnnual Review of Phytopathology, Vol. 41, No. 1IntroductionKrishna V. Subbarao22 February 2007 | Phytopathology®, Vol. 92, No. 12

Reducing Fumigant Emissions After Soil Application

ABSTRACT Volatilization and soil transformation are major pathways by which pesticides dissipate from treated agricultural soil. Volatilization is a primary source of unwanted agricultural chemicals in the atmosphere and can significantly affect fumigant efficacy. Volatile pesticides may cause other unique problems; for example, the soil fumigant methyl bromide has been shown to damage stratospheric ozone and will soon be phased out. There is also great concern about the health consequences of inhalation of fumigants by people living in proximity to treated fields. Because replacement fumigants will likely face increased scrutiny in years ahead, there is a great need to understand the mechanisms that control their emission into the atmosphere so these losses can be minimized without loss of efficacy. Recent research has shown that combinations of vapor barriers and soil amendments can be effective in reducing emissions. In this paper, some potential approaches for reducing fumigant emissions to the atmosphere are described.

Volatilization of 1,3-Dichloropropene in Florida Plasticulture and Effects on Fall Squash Production

One of the proposed alternative chemicals for methyl bromide is 1,3-D. The most common forms of 1,3-D products are cis- or trans-isomers of 1,3-D with the fungicidal agent, chloropicrin, containing such mixtures as 65% 1,3-D and 35% chloropicrin (C-35). Soil fumigants are commonly applied under a polyethylene film in Florida raised bed vegetable production. Much of the research regarding cropping system effects of alternative fumigants to methyl bromide has focused primarily on plant growth parameters, with little regard to the atmospheric fate of these chemicals. The objective of this research was to determine both the atmospheric emission of 1,3-D under different plastic film treatments and to evaluate effects of application rates of 1,3-D and C-35 on plant pests, growth, and yield of Sunex 9602 summer squash (Cucurbita pepo L.). Results showed that use of a high barrier polyethylene film (or virtually impermeable film - VIF) greatly reduced fumigant emission compared to ground cover with conventional polyethylene films or uncovered soil. Summer squash seedling survival was a severe problem in several of the 1,3-D alone treatments where no fungicidal agent was added, whereas C-35 resulted in excellent disease control at both full and one-half of the recommended application rates for this chemical. Both 1,3-D and C-35 provided good plant stands and higher yields when applied at their recommended application rates. However, all squash yields were lower than typical squash production levels due to late planting and early winter frost kill. Chemical names used: 1,3-dichloropropene (1,3-D); trichloronitropropene (chloropicrin).

Column System for Concurrent Assessment of Emission Potential and Pest Control of Soil Fumigants

AbstractFumigation for soilborne pest and pathogen control is under close scrutiny because of its potential hazardous effects on the environment and on human health. Therefore, reduced‐risk yet effective fumigation practices are imperatively needed. We have developed a column system that allows an integrated evaluation of emission potential and efficacy of fumigants. The system consists of a large, packed soil column and a sampling chamber for measuring fumigant emissions at the soil surface. Nematodes (or other pests) can be inoculated into the column and their survival may be assayed after the treatment. This approach was used to evaluate the emission of 1,3‐dichloropropene (1,3‐D) and its efficacy against the citrus nematode Tylenchulus semipenetrans when ammonium thiosulfate, a 1,3‐D degrading fertilizer, was applied at the soil surface. Results closely comparable to field observations were obtained. Compared with field studies, the proposed method is rapid and inexpensive, and thus may be used for screening fumigation practices that have improved environmental safety and pest control performance.

Effect of Application Methods on 1,3‐Dichloropropene Volatilization from Soil under Controlled Conditions

AbstractEmissions of fumigants can be an important source of air pollution at soil fumigation sites, and the high emission rates result partly from the use of application methods that are high in volatilization potential. In this study, we compared volatilization of fumigant 1,3‐dichloropropene (1,3‐D) fr.om a sandy loam in 60‐cm packed columns after applied by different methods. The most volatilization was found with injection into uncovered soil at a shallow depth (e.g., 56% loss for the 20‐cm injection) and application via surface drip irrigation (&gt;90%). Volatilization fluxes and cumulative losses, however, rapidly decreased as the injection depth was increased, and the total loss was only 27% for the 40‐cm injection. The commonly used polyethylene plastic was ineffective in reducing the volatilization because of its high permeability to 1,3‐D. Water application after the 20‐cm injection resulted in substantially reduced volatilization, but the least loss (22%) was obtained when an emulsifiable formulation of 1,3‐D, Telone SL, was drip‐applied to the subsurface at 20 cm. Our results indicate that variables most influencing 1,3‐D volatilization are injection depth and water management. By optimizing these variables, application methods with low emission potential can be developed.