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Phytopathology Jun 2024The loss of the soil fumigant methyl bromide (MeBr) and adoption of soil fumigant alternatives has been challenging for farmers, particularly for those crops in which... (Review)
Review
The loss of the soil fumigant methyl bromide (MeBr) and adoption of soil fumigant alternatives has been challenging for farmers, particularly for those crops in which pathogens previously controlled by MeBr have emerged as significant problems, but it has resulted in some unanticipated benefits for the scientific community and the environment. Applauded as one of the most effective environmental agreements to date, the universally accepted Montreal Protocol on Ozone Depleting Substances has had a significant impact on the environment, reducing the release of halogenated compounds from anthropogenic sources enough to mitigate global warming by an estimated 1.1°C by 2021. The funding associated with various MeBr transition programs has increased collaboration across scientific disciplines, commodity groups, industry, and regulatory agencies. Chemical alternatives and improved application strategies, including the development of gas-retentive agricultural films, coupled with sound efficacy data and grower ingenuity have resulted in the sustained production of many of the impacted crops; although there has been some loss of acreage and value, particularly for Florida fumigated crops, for some, value has continued to increase, allowing production to continue. The loss of a single, broad-spectrum tool for pest control has led to a deeper understanding of the specific pest complexes impacting these at-risk crops, as well as the development of new, biologically based management tools for their control while increasing our understanding of the role of the soil microbiome in pest control and crop production.
Topics: Hydrocarbons, Brominated; Fumigation; Soil; Crops, Agricultural; Agriculture; Plant Diseases
PubMed: 38427594
DOI: 10.1094/PHYTO-09-23-0345-IA -
Frontiers in Public Health 2023Methyl bromide (MB) is worldwide the only effective fumigant heavily used for quarantine pre-shipment treatment and has a critical use exemption for soil fumigations due...
Methyl bromide (MB) is worldwide the only effective fumigant heavily used for quarantine pre-shipment treatment and has a critical use exemption for soil fumigations due to its excellent permeability and insecticidal effect. However, MB should be replaced as it is an an ozone-depleting substance and also highly toxic to humans. Recently, MB has been shown to be hazardous even for asymptomatic workers, affecting their central and autonomic nervous systems. However, the effects of MB exposure on vascular health have not been explored. This study aimed to determine whether MB affects the arterial system of asymptomatic workers. We measured the second derivative of the photoplethysmogram (SDPTG) indices, which are indicators of vascular load and aging, and urinary bromide ion (Br) concentrations in 44 fumigators (study group) and 20 inspectors (control group) before and after fumigation. In fumigators, the mean values of post-work SDPTG indices (b/a, c/a, d/a, e/a, and SDPTG aging index) and Br levels were significantly changed compared to their pre-work values ( < 0.05), indicating a negative effect on their cardiovascular health. In contrast, SDPTG indices and Br levels in inspectors did not show any differences before and after work. All SDPTG indices except c/a showed significant correlations with Br levels in all individuals ( < 0.05). In conclusion, the Br levels and SDPTG indices of fumigators varied after MB work, and they experienced negative effects on their health despite being asymptomatic.
Topics: Humans; Photoplethysmography; Aging; Hydrocarbons, Brominated; Insecticides
PubMed: 37818301
DOI: 10.3389/fpubh.2023.1224143 -
Pest Management Science Dec 2023Bactrocera correcta (Bezzi) is a significant pest of the red pitaya fruit (Selenicereus undatus). This study investigated the insecticidal effects of methyl bromide (MB)...
Comparison of fumigation efficacy of methyl bromide alone and phosphine applied either alone or simultaneously or sequentially against Bactrocera correcta in Selenicereus undatus (red pitaya) fruit.
BACKGROUND
Bactrocera correcta (Bezzi) is a significant pest of the red pitaya fruit (Selenicereus undatus). This study investigated the insecticidal effects of methyl bromide (MB) alone, phosphine (PH ) alone, both applied simultaneously (PH + MB), and PH application followed sequentially by MB (PH → MB) against B. correcta in red pitaya fruits.
RESULTS
The 3 instar larvae of B. correcta were the most tolerant to MB alone and the combined treatments, whereas eggs were the most susceptible stage. Both the PH + MB and PH → MB treatments resulted in higher mortality at all stages than MB alone, demonstrating a synergistic effect between MB and PH . The toxicity of the combined treatments increased with increasing PH concentrations, with the optimal concentration recorded being 1.42 to 2.84 g m . Further probit analysis revealed that compared to the MB treatment alone, the median lethal dose values of MB in PH + MB and PH → MB treatment, were reduced to 63.73% and 66.82%, respectively. Fruit quality was not adversely affected by either of the combined treatments.
CONCLUSION
This work provides robust evidence that combining MB and PH to control B. correcta is highly effective, especially the PH → MB treatment. This combination decreased the amount of MB required for effective control at all life stages, while protecting fruit quality against MB phytotoxicity to a greater extent than conventional MB fumigation alone. © 2023 Society of Chemical Industry.
Topics: Animals; Fruit; Fumigation; Tephritidae; Phosphines; Hydrocarbons, Brominated; Cactaceae
PubMed: 37534537
DOI: 10.1002/ps.7697 -
ACS Synthetic Biology Dec 2023Soil microbial communities with reduced complexity are emerging as model systems for studying consortia-scale phenotypes. To establish synthetic biology tools for...
Soil microbial communities with reduced complexity are emerging as model systems for studying consortia-scale phenotypes. To establish synthetic biology tools for studying these communities in hard-to-image environmental materials, we evaluated whether a single member of a model soil consortium (MSC) can be programmed to report on gene expression without requiring matrix disruption. For these studies, we targeted a five-membered MSC that includes , , sp003130705, sp001905665, and . By coupling the expression of a methyl halide transferase to a constitutive promoter, we show that can be programmed to synthesize methyl halides that accumulate in the soil headspace at levels that are ≥24-fold higher than all other MSC members across a range of environmentally relevant hydration conditions. We find that methyl halide production can report on an MSC promoter that is activated by changes in water potential, and we demonstrate that a synthetic gas signal can be read out directly using gas chromatography and indirectly using a soil-derived that is programmed to produce a visual output in response to methyl halides. These tools will be useful for future studies that investigate how MSC responds to dynamic hydration conditions, such as drought and flood events induced by climate change, which can alter soil water potential and induce the release of stored carbon.
Topics: Soil; Hydrocarbons, Brominated; Water; Signal Transduction
PubMed: 37991716
DOI: 10.1021/acssynbio.3c00559 -
Environmental Science & Technology Dec 2023Methyl halides play important roles in stratospheric ozone depletion, but their formation mechanisms are not well defined. This study demonstrated that iron-based...
Methyl halides play important roles in stratospheric ozone depletion, but their formation mechanisms are not well defined. This study demonstrated that iron-based photochemistry significantly enhanced alkyl halide production by promoting the reaction of the representative monomer of lignin with halide ions in saline water under solar light irradiation. The methyl chloride (CHCl) emission from the light/Fe(III) process was 2 orders of magnitude higher than dark treatment and in the absence of iron. In addition, bromide and iodide showed better reactivity in the formation of the corresponding methyl bromide (CHBr) and methyl iodide (CHI). Alkyl halides identified from seawater, brackish water, and salt pan water under sunlight irradiation were positively correlated with the Fe(III) concentrations, indicating that iron-based photochemistry is ubiquitous. This work suggested that the photoinduced formation of methyl radical and redox cycling of iron triggered by the Fenton-like reaction are responsible for the enhanced release of alkyl halides. This study represents an abiotic formation pathway of alkyl halides, which accounts for a portion of the unidentified sources of halocarbons in the ocean.
Topics: Iron; Photochemistry; Hydrocarbons, Halogenated; Seawater; Ferric Compounds
PubMed: 38010203
DOI: 10.1021/acs.est.3c05552 -
Foodborne Pathogens and Disease Dec 2023Due to the phaseout of methyl bromide (MeBr), there is a need for broad-spectrum soil fumigation alternatives for pest management. Little is known about the impact of...
Due to the phaseout of methyl bromide (MeBr), there is a need for broad-spectrum soil fumigation alternatives for pest management. Little is known about the impact of fumigation alternatives on foodborne pathogens, such as , in agricultural soils. This study investigated the effect of MeBr alternative fumigants on reduction in soil. Sandy loam soil was collected from a conventional farmed vegetable field and inoculated with either Newport J1892 or Typhimurium ATCC 14028 (5.9 ± 0.3 log colony-forming unit [CFU]/g). Each of the four fumigants labeled for pest management (1,3-dichloropropene, chloropicrin, dimethyl disulfide, and metam sodium) was applied at labeled maximum application field levels to soil in pots and stored for a 2-week period. Sterile water was used as a control. Following the 2-week period, concentrations in soil samples were enumerated at 1, 7, 14, and 21 days postfumigation. The mean concentration of Newport was significantly higher than that of Typhimurium 1 day after fumigation ( = 0.015). Fumigation using 1,3-dichloropropene or dimethyl disulfide significantly reduced Newport and Typhimurium concentrations, compared with the sterile water control. The rate of reduction in soil treated with dimethyl disulfide was higher (0.17 ± 0.02 log CFU/g/day), compared with soil treated with the other fumigants (0.10-0.12 log CFU/g/day). Due to the reduction of , alternative fumigation treatments may mitigate potential contamination in soil within farm environments.
Topics: Soil; Salmonella enterica; Fumigation; Pesticides; Water
PubMed: 37738333
DOI: 10.1089/fpd.2023.0031 -
Applied and Environmental Microbiology Sep 2023The application of microfluidic techniques in experimental and environmental studies is a rapidly emerging field. Water-in-oil microdroplets can serve readily as...
The application of microfluidic techniques in experimental and environmental studies is a rapidly emerging field. Water-in-oil microdroplets can serve readily as controllable micro-vessels for studies that require spatial structure. In many applications, it is useful to monitor cell growth without breaking or disrupting the microdroplets. To this end, optical reporters based on color, fluorescence, or luminescence have been developed. However, optical reporters suffer from limitations when used in microdroplets such as inaccurate readings due to strong background interference or limited sensitivity during early growth stages. In addition, optical detection is typically not amenable to filamentous or biofilm-producing organisms that have significant nonlinear changes in opacity and light scattering during growth. To overcome such limitations, we show that volatile methyl halide gases produced by reporter cells expressing a methyl halide transferase (MHT) can serve as an alternative nonoptical detection approach suitable for microdroplets. In this study, an MHT-labeled reporter strain was constructed and characterized. Protocols were established for the encapsulation and incubation of in microdroplets. We observed the complete life cycle for including the vegetative expansion of mycelia, mycelial fragmentation, and late-stage sporulation. Methyl bromide (MeBr) production was detected by gas chromatography-mass spectrometry (GC-MS) from gas reporters incubated in either liquid suspension or microdroplets and used to quantitatively estimate bacterial density. Overall, using MeBr production as a means of quantifying bacterial growth provided a 100- to 1,000-fold increase in sensitivity over optical or fluorescence measurements of a comparable reporter strain expressing fluorescent proteins. IMPORTANCE Quantitative measurement of bacterial growth in microdroplets is desirable but challenging. Current optical reporter systems suffer from limitations when applied to filamentous or biofilm-producing organisms. In this study, we demonstrate that volatile methyl halide gas production can serve as a quantitative nonoptical growth assay for filamentous bacteria encapsulated in microdroplets. We constructed an gas reporter strain and observed a complete life cycle for encapsulated in microdroplets, establishing microdroplets as an alternative growth environment for spp. that can provide spatial structure. We detected MeBr production from both liquid suspension and microdroplets with a 100- to 1,000-fold increase in signal-to-noise ratio compared to optical assays. Importantly, we could reliably detect bacteria with densities down to 10 CFU/mL. The combination of quantitative gas reporting and microdroplet systems provides a valuable approach to studying fastidious organisms that require spatial structure such as those found typically in soils.
Topics: Emulsions; Fluorescence; Gases; Transferases
PubMed: 37699129
DOI: 10.1128/aem.00764-23 -
Journal of Environmental Quality 2024Methyl bromide (MeBr) is a sterilizing fumigant used to control quarantine pests that is restricted due to its detrimental atmospheric effects. The degradation of...
Methyl bromide (MeBr) is a sterilizing fumigant used to control quarantine pests that is restricted due to its detrimental atmospheric effects. The degradation of injected MeBr produces crop-available Br . Up to five applications of MeBr were used in southeastern Idaho fields to combat the pale cyst nematode (Globodera pallida). Data regarding the uptake and partitioning of Br in crops following MeBr application in the region were unavailable. Research determined background concentrations of Br in alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), corn (Zea mays L.), potato (Solanum tuberosum L.), and wheat (Triticum aestivum L.) compared to MeBr-treated fields. Background Br concentrations ranged from nondetectable (ND) to 33.0 mg Br kg ; vegetative tissue concentrations were greater than reproductive, except corn where there was no difference. Nearly all crops grown in MeBr-treated fields had greater Br concentrations than background. Background-baled-alfalfa tissue Br concentration was 33.0 mg kg compared to 117.8 mg Br kg from a MeBr-treated field. Br concentration in green alfalfa decreased from 79.8 to 36.5 mg Br kg at the final cutting in a MeBr-treated field, where time after application decreased crop Br concentrations. Small grains had low Br concentrations in reproductive tissue (1.7 mg Br kg ) compared to vegetative tissue (106.5 mg Br kg ). Corn stover concentration (12.7 mg Br kg ) was low relative to small-grain straw, but corn ear (5.8 mg Br kg ) was greater than small-grain reproductive tissue in the MeBr-treated field. Crop selection following MeBr applications should consider the likelihood of elevated Br concentration for the plant fractions intended end use.
Topics: Animals; Bromides; Fumigation; Idaho; Nematoda; Hydrocarbons, Brominated
PubMed: 37939688
DOI: 10.1002/jeq2.20529 -
Environmental Monitoring and Assessment Aug 2023Phosphine, as per several reports, is considered to be an ideal and effective alternative to methyl bromide (MB) fumigant, phased out globally honouring 'Montreal...
Phosphine, as per several reports, is considered to be an ideal and effective alternative to methyl bromide (MB) fumigant, phased out globally honouring 'Montreal Protocol'. The food grains fumigated with phosphine are perceived to be residue-free; however, estimation of its residues is imperative. In the present study, the phosphine residues were estimated in grains of wheat, rice, green gram, chickpea and yellow pea fumigated with different formulations of phosphine under 7 and 10 days exposure periods at various locations in India. For efficacy studies, the conventional aluminium phosphide (AlP) tablet (56% @2 and 3 tablet/MT) and granular AlP (77.5% @1.0 and 1.5 g phosphine/m) formulations were applied. Each treatment including untreated control was replicated thrice. The concentration was monitored every 24 h until the end of exposure periods. Food grain samples were drawn before and post fumigation following a certain waiting period for estimation of phosphine residues using gas chromatography equipped with FPD detector. Residues in fumigated food grains were observed in traces in all the experimental stacks, but below the MRL (0.1 ppm), fixed by Codex Alimentarius Commission (CAC). Phosphine can be considered safe for use as an alternate fumigant in quarantine and long-term storage of food grains leaving residues below MRL.
Topics: Environmental Monitoring; Chromatography, Gas; Aluminum; Edible Grain; Pesticides
PubMed: 37589729
DOI: 10.1007/s10661-023-11645-4