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Copyright of Argentinian Horticulture / Horticultura Argentina is the property of Revista Horticultura Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Background Soil microorganisms are integral to maintaining soil health and crop productivity, but fumigation used to suppress soilborne diseases may affect soil microbiota. Currently, little is known about the legacy effects of soil fumigation on soil microbial communities and their response to fumigation at the production scale. Here, 16S rRNA gene and internal transcribed spacer amplicon sequencing was used to characterize the bacterial and fungal communities in soils from intensively managed crop fields with and without previous exposure to metam sodium (MS) fumigation. The effect of fumigation history, soil series, and rotation crop diversity on microbial community variation was estimated and the response of the soil microbiome to MS application in an open microcosm system was documented. Results We found that previous MS fumigation reduced soil bacterial diversity but did not affect microbial richness and fungal diversity. Fumigation history, soil series, and rotation crop diversity were the main contributors to the variation in microbial β-diversity. Between fumigated and non-fumigated soils, predominant bacterial and fungal taxa were similar; however, their relative abundance varied with fumigation history. In particular, the abundance of Basidiomycete yeasts was decreased in fumigated soils. MS fumigation also altered soil bacterial and fungal co-occurrence network structure and associations. In microcosms, application of MS reduced soil microbial richness and bacterial diversity. Soil microbial β-diversity was also affected but microbial communities of the microcosm soils were always similar to that of the field soils used to establish the microcosms. MS application also induced changes in relative abundance of several predominant bacterial and fungal genera based on a soil’s previous fumigation exposure. Conclusions The legacy effects of MS fumigation are more pronounced on soil bacterial diversity, β-diversity and networks. Repeated fumigant applications shift soil microbial compositions and may contribute to differential MS sensitivity among soil microorganisms. Following MS application, microbial richness and bacterial diversity decreases, but microbial β-diversity was similar to that of the field soils used to establish the microcosms in the short-term (

Easter lily bulbs for greenhouse forcing are produced in Del Norte County, California and Curry County, Oregon, USA. Pratylenchus penetrans infestation seriously affects growth of field grown bulbs. During two consecutive years of field trials containing 22 treatments, commercially prepared formulations of essential oils (EOs) were compared to an untreated control and to a standard chemical fumigant treatment (FU) (1,3-dichloropropene and metam sodium) applied preplant followed by phorate (PH) at planting to determine their value in the management of lesion nematode, and in improving plant health. The EO products Duogard, EF400, EF300, and Cinnamite were tested as preplant dips to bulblet planting stock. The treated bulblets were tested either alone, in combination with PH at-planting, at planting following FU or in combination with PH at planting following FU. The organophosphates ethoprop and fosthiazate were also tested either alone, or at a reduced rate in combination with a reduced rate of PH. With respect to bulb circumference, ten treatments consistently outperformed the control. In consecutive years, three treatments had healthier looking roots than the control. At harvest, levels of lesion nematode within roots were consistently lower in nine treatments. EOs were beneficial in mitigating nematode damage.Easter lily bulbs for greenhouse forcing are produced in Del Norte County, California and Curry County, Oregon, USA. Pratylenchus penetrans infestation seriously affects growth of field grown bulbs. During two consecutive years of field trials containing 22 treatments, commercially prepared formulations of essential oils (EOs) were compared to an untreated control and to a standard chemical fumigant treatment (FU) (1,3-dichloropropene and metam sodium) applied preplant followed by phorate (PH) at planting to determine their value in the management of lesion nematode, and in improving plant health. The EO products Duogard, EF400, EF300, and Cinnamite were tested as preplant dips to bulblet planting stock. The treated bulblets were tested either alone, in combination with PH at-planting, at planting following FU or in combination with PH at planting following FU. The organophosphates ethoprop and fosthiazate were also tested either alone, or at a reduced rate in combination with a reduced rate of PH. With respect to bulb circumference, ten treatments consistently outperformed the control. In consecutive years, three treatments had healthier looking roots than the control. At harvest, levels of lesion nematode within roots were consistently lower in nine treatments. EOs were beneficial in mitigating nematode damage.

The stem and bulb nematode Ditylenchus dipsaci is one of the most important plant-parasitic nematodes with a worldwide distribution, causing damage mainly in temperate regions. Onion, garlic and alfalfa are its main hosts. The use of nematode-free seeds and plant propagation materials, crop rotation, resistant cultivars and chemical nematicides are common methods of its management. Due to the side effects of nematicides on human health and the environment, the use of safe, cost-effective alternative methods are necessary. In this study, the nematicidal effects of the essential oils of mountain thyme, oregano, clove, sage and savory as well as the metabolites of the fungus Scytalidium sp. were studied in comparison to metam sodium under laboratory conditions. To prepare the nematode population, nematodes were extracted from naturally infected garlic from the Gogan region of East Azarbaijan province, reared on carrot discs and incubated at 18 ± 1°C for 60 days. The effects of plant essential oils, fungal metabolites and metam sodium were investigated in bioassays with four replicates, and nematode mortality was recorded after 24 and 48 hours. After a probit analysis, the LC50 and LC90 values were calculated for each of the compounds tested. After 24 hours, the LC50 values for the essential oils clove, oregano, marzeh and thyme were 1748, 769.2, 1662 and 4913 ppm, respectively, and for the fungal metabolite and metam sodium were 207.6 and 6.7 ppm, respectively. Gas chromatography with a mass spectrometer (GC-MS) and a DB5 column was used to identify the components of the essential plant oils and the metabolites, the results of which are presented here. Based on the LC50 values, the compounds tested caused mortality and population decline of D. dipsaci at relatively low concentrations, with the exception of sage-flower. [ABSTRACT FROM AUTHOR]

Background: Soil microorganisms are integral to maintaining soil health and crop productivity, but fumigation used to suppress soilborne diseases may affect soil microbiota. Currently, little is known about the legacy effects of soil fumigation on soil microbial communities and their response to fumigation at the production scale. Here, 16S rRNA gene and internal transcribed spacer amplicon sequencing was used to characterize the bacterial and fungal communities in soils from intensively managed crop fields with and without previous exposure to metam sodium (MS) fumigation. The effect of fumigation history, soil series, and rotation crop diversity on microbial community variation was estimated and the response of the soil microbiome to MS application in an open microcosm system was documented. Results: We found that previous MS fumigation reduced soil bacterial diversity but did not affect microbial richness and fungal diversity. Fumigation history, soil series, and rotation crop diversity were the main contributors to the variation in microbial β-diversity. Between fumigated and non-fumigated soils, predominant bacterial and fungal taxa were similar; however, their relative abundance varied with fumigation history. In particular, the abundance of Basidiomycete yeasts was decreased in fumigated soils. MS fumigation also altered soil bacterial and fungal co-occurrence network structure and associations. In microcosms, application of MS reduced soil microbial richness and bacterial diversity. Soil microbial β-diversity was also affected but microbial communities of the microcosm soils were always similar to that of the field soils used to establish the microcosms. MS application also induced changes in relative abundance of several predominant bacterial and fungal genera based on a soil's previous fumigation exposure. Conclusions: The legacy effects of MS fumigation are more pronounced on soil bacterial diversity, β-diversity and networks. Repeated fumigant applications shift soil microbial compositions and may contribute to differential MS sensitivity among soil microorganisms. Following MS application, microbial richness and bacterial diversity decreases, but microbial β-diversity was similar to that of the field soils used to establish the microcosms in the short-term (< 6 weeks). The responses of soil microbiome to MS fumigation are context dependent and rely on abiotic, biotic, and agricultural management practices. [ABSTRACT FROM AUTHOR]

Soil fumigation is commonly employed for pest control in potato production, although it can unintentionally harm non-target organisms in the soil. The presence of cover crops can significantly influence the abundance and composition of microorganisms. However, there is limited knowledge regarding the combined impact of soil fumigation and cover crops on soil health in potato fields. To address this knowledge gap, a field study was conducted at the Hermiston Agricultural Research and Extension Center, Oregon State University with a randomized split-plot design consisting of four fumigation treatments (no fumigation control, Telone, metam sodium, and co-applied Telone and metam sodium) as the main plots and five cover crop treatments [no cover crop, wheat (Triticum aestivum), mustard (Brassica nigra), radish (Raphanus sativus), and a mixture of winter pea (Pisum sativum) and faba bean (Vicia faba)] as the subplots. Compared to the control, microbial biomass carbon (MBC) in non-fumigated soils of pea+faba bean, wheat, and radish increased by 41 %, 37 %, and 31 %, respectively. In soils treated with metam sodium, pea+faba bean, wheat, radish, and mustard increased MBC by 30 %, 34 %, 41 %, and 40 % compared to the control. The results demonstrated the potential of cover crops to enhance MBC after fumigation. Both Fumigation and cover crop did not impact the total yield of potatoes, although fumigation increased the yield of tubers within 171-283 g size category compared to the control. However, the current data is not sufficient for making a conclusive remark. Further field studies should be conducted to understand the role of fumigation and cover crops on potato soil health and potato production., Competing Interests: Declaration of competing interest The authors declare no competing financial interests or personal relationships that could have influenced the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Chemical fumigation and biofumigation are used to reduce soil-borne diseases in agricultural production systems; however, nontargeted soil microorganisms may also be affected. This study compared the effects of chemical fumigation, either used alone or combined with an organic amendment, and biofumigation on soil bacterial community diversity and composition under controlled conditions over 160 days. Treatments included: fumigation with chloropicrin (CP), fumigation with metam sodium used alone (MS) or combined with barley plant residues (MSBR), biofumigation with mustard plant residues, addition of barley plant residues and untreated control. Biofumigation had a greater impact on bacterial diversity at early time points, transiently decreasing species evenness and yielding the most dissimilar β-diversity after 3 days. MS fumigation did not affect bacterial diversity indices; however, MSBR transiently decreased species evenness after 8 days. CP-treated soil had decreased species evenness that did not recover over time and had the most dissimilar β-diversity at the end of the incubation compared with all other treatments. This study demonstrated that CP fumigation had the greatest and most persistent impact on bacterial diversity, whereas MS fumigation and biofumigation led to transient decreases in bacterial diversity. [ABSTRACT FROM AUTHOR]

Fumigation is a widely applied approach to mitigate the soil-borne diseases. However, the potential effects of currently applied fumigants on ammonification remain unclear. An 84-day incubation experiment was conducted based on non-fumigated soil (CK) and fumigated soil using three common fumigants, i.e., chloropicrin (CP), 1,3-dichloropropene (1,3-D), and metam sodium (MS). The results showed that, the three fumigants all decreased the microbial C, and the largest reduction (84.7%) occurred with the application of CP. After fumigation, the microbial diversity in the CP treatment rapidly recovered, but that in the 1,3-D treatment decreased and did not recover by the end of the experiment. The application of MS showed no impact on the microbial diversity during the assay, indicating that significantly different microbial diversity can be achieved by choosing different fumigants. Furthermore, the three fumigants showed divergent effects on the enzymes involved in ammonification. The analysis showed that the enzyme variation with CP application was mainly associated with the changed microbial C and N (P

Clover cyst nematode, Heterodera trifolii, is one of the most important plant-parasitic nematode on Kimchicabbage in highland in Korea. Recently, a demand of soil disinfection machine for fumigants is increasing. This study was conducted to assess the control effects of a newly developed prototype soil disinfection machine to the cyst nematode. Two fumigants, dimethyl disulfide (DMDS) and metam sodium (MNa), were treated using the machine in a field, which was infected with the cyst nematode. After 4 weeks, control effects of fumigants were assessed as eggs hatching rates inside of cysts extracted from the soil, and as a number of females reproduced in roots of Kimchi-cabbage. DMDS (39 l/10 a) suppressed over 99.0% of the eggs hatching rate and the number of females reproduced. On the other hand, MNa (29 l/10 a) controlled the egg hatching rates from minimum 78.3% to maximum 99.4%, and the number of females from 34.7% to 49.3%. The control effects of two fumigants to clover cyst nematode by treated depth were no significant differences statistically. These results showed that DMDS treatment using the soil disinfection machine was expected to have the control effects for the clover cyst nematode.

In North America, potato early dying is often controlled using soil fumigants. Fumigants confer benefits on plant health but also impact soil microbial activity, including nitrogen (N) cycling. The purpose of this study was to evaluate the effects of two soil fumigants, chloropicrin and metam sodium, on potato crop yield, N uptake, and N use efficiency (NUE), as well as soilborne pathogens, soil microbial respiration rates and soil concentrations of NH4+-N and NO3−-N. We established a field study with a split-plot randomized complete block design in 2016 and 2017, with whole plots divided among three fumigation treatments (no fumigant, chloropicrin, or metam sodium) and split into five subplots, each receiving a different total application rate of N (45, 135, 202, 269, or 336 kg·ha−1 N). Both fumigants suppressed Verticillium dahliae propagule concentrations and foliar symptoms of potato early dying while increasing yield, final tuber set, N uptake, and NUE. Fumigation did not affect the agronomic optimum N rate, nor the response of marketable yield to N rate, but it did increase yield per unit N applied (partial factor productivity) by 16% and 35% over the non-fumigated controls in 2016 and 2017, respectively. Chloropicrin, but not metam sodium, reduced the prevalence of common scab symptoms in tubers. Both fumigants decreased microbial respiration rates before planting and at midseason. Fumigants reduced nitrification rates before planting and at midseason, with chloropicrin having a particularly strong effect before planting. While fumigation conferred benefits to yield and NUE, its effects on microbial community structure and function merit further study. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND Chloropicrin (PIC) mixtures of 1,3‐dichloropropene and chloropicrin (DD:PIC), dazomet, and metam sodium (MS) have been applied as chemical alternatives to methyl bromide (MB) in Spanish strawberry nurseries since MB was banned as a soil fumigant in 2005. These chemical alternatives were applied to soil in two Spanish strawberry nurseries between 2003 and 2017 to test their efficacy against the main crown and root disease and soil fungal populations in comparison with the use of MB and PIC (MB:PIC). These chemicals were applied at several doses with different application methods under plastic films. Crown and root disease incidence was calculated as the percentage of plants with symptoms caused by soil‐borne pathogens. Soil fungal populations were estimated as colony forming units per gram of dry soil. RESULTS: All chemicals significantly reduced soil‐borne fungal disease incidence and fungal population in both nurseries over the years. Phytophthora cactorum and Fusarium spp. were the main pathogens causing soil‐borne diseases, followed by Verticillium spp. MB:PIC remained the treatment that best controlled P. cactorum. MS and DD:PIC controlled Fusarium disease to a lesser extent than MB:PIC and dazomet in both nurseries. MB:PIC and PIC were the two treatments that most reduced Verticillium spp. The population of Verticillium spp. declined and the presence of other species such as Colletotrichum spp. and Rhizoctonia spp. was minimal during the study. CONCLUSION: Chemicals are necessary to obtain healthy strawberry plants. The use of chemical alternatives to MB has resulted in changes in the incidence of soil‐borne diseases and soil fungal populations in strawberry nurseries. Dazomet was an effective alternative to MB as a soil‐borne disease control, except against Verticillium spp. MB alternatives in strawberry nursery soils have caused Fusarium spp. to displace Verticillium spp. [ABSTRACT FROM AUTHOR]

Sustainable agriculture requires soil management practices that increase productivity while minimizing detrimental impacts on soil health. Soil fumigation is a common practice which controls soil-borne diseases and promotes yield, but can potentially influence soil health by suppressing soil microorganisms. Considering the wide use of fumigation, we still lack a complete understanding of its effects on soil health, which prevents us from understanding the resilience of agricultural ecosystems and prescribing management activities accordingly. Moreover, soils are highly variable, and so both the agronomic benefits and any negative impacts of fumigation on soil health may vary across soil types. In this study, we investigated the impact of metam sodium fumigation on a variety of soil health indicators using the potato fields of Wisconsin, USA. We collected soil and potatoes from 7 commercial potato fields subjected to fumigation and non-fumigation treatments, representing two distinct growing regions. We measured the effect of fumigation on tuber yield and soil-borne diseases, soil chemistry, microbial activities and community structure. Fumigated plots showed higher potato yield as well as bacterial diversity and microbial-mediated carbon retention than unfumigated plots in central sandy soils; the opposite trend was observed in northern loamy soils. We also found that soil bacterial community diversity was closely associated with yield responses to fumigation. We concluded that fumigation has varying effects on selected soil health indicators depending on the soil conditions. Sustainability of soil health is largely dependent on the soil microbiome, as negative feedback may be more likely to happen where microbial diversity is sensitive to fungicide application. • Metam sodium fumigation influenced soil health indicators. • Fumigation effect varied depending on the soil type. • Soil bacterial diversity is related to potato yield responses to fumigation. [ABSTRACT FROM AUTHOR]

Methyl bromide is highly effective in reducing soil pathogens. Although its use was to be phased out completely in the United States by Jan. 1, 2005, due to environmental concerns, a 1-year critical-use exemption will allow tree fruit growers to use the fumigant through the end of the year. To explore possible replacements for methyl bromide, we compared the effects of pre- and postplant treatments and amendments on soil microbial communities and tree vigor in a replanted peach orchard. Both soil sterilization treatments and organic carbon amendments changed the composition of microbial communities in the soil. High microbial biomass is generally considered beneficial to agricultural soils; we found that it was usually highest in soils that received the organic carbon amendment and lowest in those with soil sterilization. However, tree vigor was highest with the sterilization treatments. The effects of a microbial inoculants/organic carbon combination on microbial communities and plant vigor were no different from simply adding organic carbon.

Organic farmers and limited-resource growers in the San Joaquin Valley and other agricultural areas in California — many of whom are ethnic minorities — encounter limited options and environmental constraints when seeking economically viable pest management methods. Over the past 8 years, we have conducted weed research and implementation projects on soil solarization at the UC Kearney Research and Extension Center and on farms in the surrounding San Joaquin Valley. In the Kearney studies, small-scale solarization in parsley reduced weed biomass 94% to 99% over the untreated control. Furthermore, in an on-farm study, solarization provided effective weed control for strawberries at a much lower cost than methyl bromide, with comparable yields. This research has provided guidelines and technical support for growers wishing to implement solarization and related techniques for nonchemical soil disinfestation in a wide variety of specialty crops.

Graphical abstract Highlights • Ammonium bicarbonate/metam sodium fumigation plus heat alleviated Fusarium wilt. • Ammonium bicarbonate/metam sodium fumigation plus heat improved fruit quality. • Ammonium bicarbonate/metam sodium fumigation plus heat balanced soil micro-ecology. • Ammonium bicarbonate/metam sodium fumigation plus heat improved soil properties. Abstract The induction of Fusarium wilt by continuous cropping has become a severe problem for watermelon cultivation around the world. Here, the feasibility and underlying mechanism of soil fumigation with ammonium bicarbonate (AB) or metam sodium (MS) under high temperature (HT) were investigated for the control of Fusarium wilt during watermelon growth on continuously cropped soils. Both AB + HT and MS + HT decreased the density of Fusarium oxysporum f. sp. niveum (FON) in soil, improved the soil properties (i.e. increased the pH, reduced salinity, improved soil nutrients, balanced soil micro-ecology, and increased soil enzyme activities), and consequently decreased the Fusarium wilt incidence and improved the watermelon fruit quality. In vitro , MS treatment stopped the growth of FON on medium, while AB mixed with lime (but not AB) alone inhibited FON growth. AB or MS fumigated soils under HT also decreased Fusarium wilt incidence of watermelon seedlings after artificial FON infection. Consequently, AB + HT and MS + HT can control continuous cropping-induced Fusarium wilt by both inhibiting FON growth and improving the soil environment. [ABSTRACT FROM AUTHOR]

Abstract A decline in red raspberry (Rubus idaeus) crop longevity has been partially attributed to parasitism by the plant-parasitic nematode Pratylenchus penetrans. Soil fumigation with 1,3-dichloropropene (1,3-D) and chloropicrin is the most common management practice for P. penetrans in this production system, but the effects are variable and there are strict regulations regarding application; alternatives are needed. A three-year study was conducted in a replanted commercial red raspberry field with a history of P. penetrans to evaluate brassicaceous seed meal (BSM) soil amendment combined with root inoculum removal (RR) as preplant alternatives to traditional soil fumigation with 1,3-D and chloropicrin. Additionally, the fumigant metam sodium at full and half rates with root removal was evaluated. Treatments were applied once prior to planting and included: BSM at 3.4 t ha−1 with RR, full rate metam sodium (692 L ha−1; Max Fum) with RR, half rate metam sodium with RR (Min Fum), and full rate metam sodium without RR (Max Fum–RR; control). Data collected included: P. penetrans population dynamics in soil and raspberry roots, microbial (bacterial and fungal) communities in soil, raspberry vegetative growth, estimated yield, and fruit total soluble solids (TSS) concentration. Population densities of P. penetrans in soil and roots were significantly higher in BSM (983–4801 P. penetrans g−1 of root) than in Max Fum and Max Fum–RR (32–802 and 40–1509 P. penetrans g−1 of root, respectively) during the first two years of the study. By the end of the study there were no differences in P. penetrans population densities among the treatments. Root removal did not affect P. penetrans densities as there were no significant differences between Max Fum and Max Fum–RR. Min Fum was more effective than BSM at reducing P. penetrans population densities, but not as effective as Max Fum or Max Fum-RR. The only difference among treatments regarding the soil microbial community was observed in the first spring after treatment application, when BSM had a soil bacterial community that differed from the other treatments; this difference did not persist into the next sampling date. The most noticeable differences in bacterial and fungal soil communities were due to season, not treatment. There were no significant differences in raspberry vegetative growth the first summer after planting. Yield or TSS did not differ in the second and third summer after planting. The current data show that Min Fum, BSM amended to soil at this experimental rate, and root removal are not effective in reducing P. penetrans population densities, but yield and fruit quality are not compromised under the conditions of the experiment. [ABSTRACT FROM AUTHOR]

Metam sodium is a widely used soil fumigant for Verticillium wilt management in most potato production regions of the United States. Environmental concerns regarding volatilization losses have led to restrictions on the use of metam sodium. The potato industry adapted to these restrictions by replacing metam sodium applications through sprinkler irrigation with shank injection applications of the fumigant. Previous research established parameters for effective shank application of metam sodium based on soil temperature, injection depth and rate of fumigation. However, these recommendations were based on research conducted under coarse-textured soil conditions with a low organic matter (OM) content (<1.3%). However, many potato production soils in North Dakota and Minnesota have a finer silt loam texture and OM contents of >2.5%. Therefore, it is important to know whether metam sodium fumigation recommendations for coarse-textured soils can be adapted to fine-textured soils. Two field trials were conducted using a split strip-block design for studying metam sodium efficacy in managing wilt. In both years, metam sodium injection depth and soil temperature at the time of injection did not result in significant differences in any study variable evaluated. All metam sodium fumigation rates significantly (P < 0.05), lowered Verticillium microsclerotia, reduced wilt severity, and improved tuber yield compared to non-treated plots. However, significant differences among fumigation rates were not observed across any variable evaluated. A relatively low rate of 373 l/ha is as effective as higher metam sodium rates for effective control of Verticillium wilt. Results presented here suggest that current metam sodium recommendations for shank injection applications in coarse-textured soils can be implemented in field soils with a fine texture and higher OM content. [ABSTRACT FROM AUTHOR]

Metam sodium is a fumigant used as a crop pretreatment in agriculture to control a wide array of pests, and soil borne diseases that may adversely affect plant quantity and quality. This present study utilized control and treated field plots to examine the effects of metam sodium on indigenous soil microbes in terms of numbers, activity, and diversity. Following metam sodium application, culturable heterotrophic counts in all soils increased significantly for 24 h, but quickly returned back to original levels. Application resulted in decreased microbial activity, detected by ATP-based assays, that was significantly lower in treated soils than control plots, but recovered quickly. High-throughput sequencing of the 16S rRNA gene showed that treated plots contained significantly lower numbers of observed OTUs, particularly 14, 21, and 28 days after treatment. Soil bacterial communities were significantly altered by MS-treatment due to increased relative abundances of Actinomycetales, Bacilli, and Chloroflexi, as well as decreased Acidobacteria. These dominant taxa observed in MS-treated plots are major contributors to biological activity in various healthy soils and rhizospheres. Therefore, the increase in relative abundance of these biologically productive phyla coupled with abundant ATP production suggests that soil health recovered following MS-treatment and remained functionally intact. [ABSTRACT FROM AUTHOR]

Cognitive integrity is a critical aspect of neurological function, and a decline in cognitive function is a hallmark of neurotoxicity. Oxidative stress is a significant pathological feature contributing to cognitive deficits that can arise from exposure to environmental pollutants such as pesticides. Among these, Metam sodium-based pesticides (MS-BP) are an emergent type of pesticide widely used in the agriculture and public health sectors for controlling pests and diseases. Our prior research has shown that animals exposed to MS-BP during the early stages of brain development caused cognitive impairments. In the present study, we tested whether exposure to this compound in a fully matured brain would affect cognitive performance and induce oxidative damage to the central nervous system. In this context, adult mice received chronic treatment with increasing doses of MS-BP and subjected to a set of behavioral paradigms. Following behavioral assessment, oxidative stress and glial activation were evaluated. Our main findings showed that MS-BP chronic exposure impaired recognition and short- and long-term memory. These alterations were accompanied by increased superoxide dismutase activity and malondialdehyde level and a marked decrease in catalase activity in specific brain areas. Moreover, exposure to MS-BP is associated with a significant rise in the density of astrocytic and microglial markers, indicating a possible glial cell response within the prefrontal cortex and hippocampus. The present work demonstrated that MS-BP altered cognitive performance likely through oxidative damage to the brain. • Exposure to MS-BP impaired recognition memory in treated animals. • Exposure to MS-BP affected short- and long-term memory in treated animals. • It affected antioxidant enzymes and lipid peroxidation indicating oxidative stress. • It raised astrocytic and microglial activation-related neuroinflammatory markers. [ABSTRACT FROM AUTHOR]

Chemical fumigation is used to reduce soil-borne diseases in agricultural production systems; however, non-targeted soil microorganisms may also be affected. This study investigated the effects of chemical fumigation and substrate carbon (C) availability on the soil bacterial and fungal community diversity under controlled conditions over 128 days. This study consisted of a 3 × 3 factorial arrangement of three fumigant treatments (fumigation with chloropicrin [CP], metam sodium [MS], or no fumigation) and three soil amendment treatments (amendment with young barley, mature barley, or no amendment). MS fumigation transiently decreased bacterial species evenness when combined with young barley residues; however, it did not affect fungal diversity indices. CP fumigation, regardless of soil amendment or substrate C availability, decreased bacterial species evenness and richness that did not recover over time. However, CP fumigation only decreased fungal species evenness and richness when combined with young or mature barley residues. Although all treatments resulted in a bacterial and fungal community that was significantly dissimilar to the non-fumigated unamended soil, CP fumigated soils had the most dissimilar bacterial and fungal β-diversity after 128 days. This study demonstrated that the addition of young or mature barley residues to chemically fumigated soil did not recover microbial diversity. Instead, the addition of plant residues to chemically fumigated soil had a greater impact on microbial diversity and community composition compared to chemical fumigation used alone, subsequently promoting a less diverse and selective community for both fumigation and organic C additions. • MS only decreased bacterial species evenness when combined with young barley. • MS did not affect fungal species evenness or richness. • CP decreased bacterial and fungal species evenness and richness. • CP greatly altered the soil bacterial and fungal community composition overtime. • CP applied alone or with barley plant residues greatly impacted the soil microbiome. [ABSTRACT FROM AUTHOR]

1,3-Dichloropropene (1,3-D), metam sodium (MS), and dazomet (DZ) are widely used as preplant soil fumigants to solve soilborne problems. To provide a more scientific and accurate evaluation of 1,3-D, MS, and DZ toxicity to the earthworm Eisenia fetida, modified artificial soil test and natural soil test were studied. The suitable soil moisture to maintain over 90% survival of the earthworms after 4 weeks of treatment in an enclosed system for modified artificial soil test and natural soil test were 26.9 to 86.4% of water-holding capacity (WHC) and 66.2 to 84.3% of WHC, respectively. The optimal soil moisture levels for modified artificial soil test and natural soil test (75 and 55% of WHC, respectively) were finally used to evaluate the toxicity of 1,3-D, MS, and DZ on earthworms. Each desiccator with 10 earthworms and natural or artificial soil was stored at 20 ± 1 °C under constant light of 400 to 800 lx for 2 weeks. The modified artificial soil test showed LC values for 1,3-D, MS, and DZ of 3.60, 1.69, and 5.41 mg a.i. kg soil, respectively. The modified natural soil test of the fumigants showed similar LC values of 2.77 and 0.65 mg a.i. kg soil, except for DZ at 0.98 mg a.i. kg soil. The present study confirms that both modified artificial soil test and modified natural soil test offer standard methods for acute toxicity test of 1,3-D, MS, and DZ on the earthworms and scientific evidences for assessing the effects of soil fumigants on non-target organisms in the soils. [ABSTRACT FROM AUTHOR]

The following work was initiated to determine the scope of application methodology and fumigant combinations for increasing efficacy of 1,3-dichloropropene (1,3-D) and metam sodium for management of root-knot nematodes (Meloidogyne spp.) in Florida. A series of five experiments were set up during spring and fall seasons to evaluate the potential of different fumigants, alone or in combination, in polyethylene film tomato production. The most promising chemical alternatives to methyl bromide, in terms of root-knot nematode management, were the combinations 1,3-D-chloropicrin, chloropicrin-proprietary solvent, and 1,3-D-metam sodium. Sprayed or injected metam sodium generally provided only short-term nematode management and by harvest nematode infection was not different from the nontreated control. Drip-applied metam sodium gave good nematode management under high nematode pressure, but needs further verification to establish (i) the importance of soil moisture and temperature on treatment efficacy and (ii) whether similar management can be obtained with fewer than three drip tubes. Broadcast applications of 1,3-D showed better efficacy as compared to applications on a preformed raised bed. Fumigation did not increase tomato yields in spring when root-knot nematode pressure was low, but during fall all chemical treatments increased yields three to five-fold, as root-knot nematode was a major yield-limiting factor. [ABSTRACT FROM AUTHOR]

Soil solarization is a non-chemical soil disinfestation method proven effective against soil-borne pathogens and weeds. However, it should be assessed under local cropping conditions before it can be implemented in commercial crops, since the process is highly dependent on climate conditions, among other factors. Soil biosolarization combines biofumigation with solarization to improve its effectiveness but knowledge about its use on tomato crops is still rather scarce and limited to nematode control. We have tested the effectiveness of soil solarization, biosolarization and fumigation with metam sodium over three tomato cropping seasons, to control corky root caused by Pyrenochaeta lycopersici and weeds under screen-house conditions in the Canary Islands (Spain). During the three seasons, maximum soil temperatures at 10 cm depth in solarized and biosolarized plots were about 10 °C higher than in controls, rising up to 41.4–43.3 °C in solarization and 43.0–44.7 °C in biosolarization, with an accumulated number of hours exceeding 40 °C of 48.8–138.2 and 92.3–204.7 h in solarized and biosolarized plots, respectively. The most effective treatment was biosolarization, which significantly increased tomato yield by 12.4% in 2001–02; 22.8% in 2002–03 and 22.2% in 2003–04, and reduced corky root severity in the last two seasons. Corky root was also significantly reduced by solarization in 2003–04, whereas there was no difference between metam sodium and control plots in any season. Weed infestation was evaluated in 2002–03 and 2003–04, in which weed density in biosolarized plots was significantly lower than in controls (88.8% and 50.6% reduction at 45 and 165 days after tomato transplanting in 2002–03; and 69.6% after 120 days in 2003–04). In contrast, weeds were not controlled by solarization, and inconsistent results were obtained with metam sodium. Here we show that soil biosolarization is clearly a way to improve the effectiveness of soil solarization under less favorable environmental conditions, like those prevailing in tomato screen-houses in the Canaries, and a feasible alternative to chemical fumigation for the control of corky root and weeds. [ABSTRACT FROM AUTHOR]

Temperature is a major environmental factor influencing land surface volatilization at the time of agricultural field fumigation. Cooler fumigation soil temperatures relevant to Pacific Northwest (PNW) application practices with metam sodium/potassium should result in appreciably reduced methyl isothiocyanate (MITC) emission rates, thus minimizing off target movement and bystander inhalation exposure. Herein, a series of laboratory controlled flow-through soil column assessments were performed evaluating MITC emissions over the range of cooler temperatures (2-13°C). Assessments were also conducted at the maximum allowed label application temperature of 32°C. All assessments were conducted at registration label-specified field moisture capacity, and no more than 50% cumulative MITC loss was observed over the 2-day post-fumigation timeframe. Three-fold reductions in MITC peak fluxes at cooler PNW application temperatures were observed compared to the label maximum temperature. This study supports current EPA metam sodium/potassium label language that indicates surface fumigations during warmer soil conditions should be discouraged. [ABSTRACT FROM AUTHOR]

Epidemiological studies suggest neurological disorders have been associated with the co-exposure to certain pesticides and transition metals. The present study aims to investigate whether co-exposure to the widely-used pesticide metam sodium and copper (Cu2+) or zinc ion (Zn2+) is able to cause synergistic neurotoxicity in neural PC12 cells and its possible mechanism(s). We found that both metam/Cu2+ and metam/Zn2+ synergistically induced apoptosis, intracellular Cu2+/Zn2+ uptake, reactive oxygen species (ROS) accumulation, double-strand DNA breakage, mitochondrial membrane potential decrease, and nerve function disorder. In addition, metam/Cu2+ was shown to release cytochrome c and apoptosis-inducing factor (AIF) from mitochondria to cytoplasm and nucleus, respectively, and activate the caspase 9, 8, 3, 7. However, metam/Zn2+ induced caspase 7 activation and AIF translocation and mildly activated cytochrome c /caspase 9/caspase 3 pathway. Furthermore, metam/Cu2+ activated caspase 3/7 by the p38 pathway, whereas metam/Zn2+ did so via both the p38 and JNK pathways. These results demonstrated that metam/Cu2+ or metam/Zn2+ co-exposure cause synergistic neurotoxicity via different mechanisms, indicating a potential risk to human health when they environmentally co-exist. [Display omitted] • Metam sodium and copper or zinc cause synergistic neurotoxicity in PC12 cells. • Metam sodium and copper or zinc induce subcellular damage and nerve function disorder. • Metam sodium and copper or zinc induce apoptosis via different mechanisms. [ABSTRACT FROM AUTHOR]

Metam sodium-based pesticide (MS-BP) is widely used in agriculture and public health. We have previously demonstrated that maternal exposure to MS-BP resulted in sensorimotor alterations in mice offspring with long-lasting deficits including anxiety- and depression-like behaviors. Here, we project to verify whether these two neurobehavioral effects occur during adulthood following direct exposure to MS-BP and whether it results in changes in the serotoninergic system and gut microbiota. Our findings showed that chronic exposure to MS-BP increased anxiety- and depression-like behaviors, accompanied by a depletion of serotonin-like neurons within the dorsal raphe nucleus and a reduction in serotoninergic terminals in the infralimbic cortex and the basolateral amygdala. In addition, all MS-BP-exposed animals exhibited a reduced total bacterial number and diversity of gut microbiota. Taken together, our data demonstrated that MS-BP-induced behavioral changes could be related to the impairment of the serotoninergic system and gut microbiota dysbiosis. • Chronic exposure to MS elevated anxiety-like behavior in treated animals. • Chronic exposure to MS increased depression-like behavior in exposed groups. • MS reduced 5-HT neurons in the dorsal raphe nucleus in treated groups. • MS reduced 5-HT terminals within the infralimbic cortex and basolateral amygdala. • MS reduced abundance and diversity of gut microbiota resulting in gut dysbiosis. [ABSTRACT FROM AUTHOR]

The impact of methyl bromide (MB) phase-out on important fruit and nursery industries in the EU (2005/2008) has been significant. Under EU Regulation 1107/2009, MB fumigant alternatives 1,3-dichloropropene and chloropicrin were also phased out (in 2010 and 2013, respectively) while dazomet, metam sodium, and potassium were re-approved with crucial restrictions of rates and years of application. However, currently an EU Member State may authorize use of these phased-out fumigants for 120 days/year. This exemption has been used for strawberry (fruit and nursery production) and other crops in Spain, Italy, Belgium, France, UK, Cyprus, Malta, and Greece in recent years. To provide an update of the current situation, a comprehensive survey of 41 European and other industries has been completed. Most of them use crop rotation as the main pest management solution. Non-chemical solutions, in particular soilless cultivation, are important in the UK, Ireland, France, the Netherlands, and Belgium. Chemical fumigation is still important in Spain, Italy, Morocco, Turkey, France, and Belgium. [ABSTRACT FROM PUBLISHER]

We evaluated the effectiveness of alternative fumigants on weed control and plant productivity in two nurseries located at high elevation and low latitude (Ciudad Guzman, Jalisco), during 2013 and 2014 at Driscoll’s and Lassen Canyon South nurseries. Treatments were: MB:chloropicrin (MB:CP); 1,3-dichloropropene:CP; CP alone; metam sodium (MS) alone; dimethyl disulphide (DMDS):CP; and sequentially applied CP and MS. A rotary spading machine was used for MS and CP followed by MS. All treatments produced similar pest suppression and runner-plant yields during 2013 and 2014. However, CP alone showed very poor control of the most abundant weed (barnyardgrass,Echinochloa crus-galli). Two years of work on MB alternatives were not sufficient to provide reliable recommendations on this critical need, therefore, the Methyl Bromide Technical Options Committee recommended critical use nomination for MB in 2015. [ABSTRACT FROM PUBLISHER]

Preplant soil fumigation is commonly used to control soilborne pathogens and weeds in forest seedling nurseries of Oregon and Washington. However, lower chemical inputs are desired to meet state and federal application regulations, to minimize buffer zone size requirements, and to help protect the environment. Therefore, the objectives of this research were to evaluate the efficacy of three reduced rate soil fumigants under totally impermeable film (TIF) in managing soilborne diseases and weeds, and to determine if combined applications of up to four biocontrol agents improved soilborne disease control. Reduced rates of methyl bromide, metam sodium, and 1,3-dichloropropene, all applied in combination with chloropicrin, were effective in decreasing soil populations of Pythium and Fusarium as well as the presence of Pythium in root debris from the previous crop. The roots of Douglas-fir ( Pseudotsuga menziesii ) seedlings transplanted into each fumigant treatment were also colonized less by Pythium and Fusarium than those transplanted into nonfumigated control plots. However, biocontrol treatments were not effective against either pathogen. Weed biomass and weeding times were also significantly reduced by fumigation. Application costs were similar for all three fumigant treatments, but seedling size was largest from the methyl bromide and metam sodium treatments followed by the 1,3-dichloropropene treatment. Based on the results of this study, reduced rates of methyl bromide, metam sodium, and 1,3-dichloropropene show promise in managing soilborne diseases and weeds in forest nurseries. [ABSTRACT FROM AUTHOR]