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The combination of dimethyl disulfide (DMDS) and dazomet (DZ) is a potential alternative to methyl bromide (MB) for soil disinfestation. The efficacy of DMDS plus DZ in controlling key soilborne pests was evaluated in a laboratory study and in two commercial cucumber greenhouses. Laboratory studies found that all of the combinations had positive synergistic effects on root-knot nematodes, two key soilborne fungi, and two major weed seeds. Greenhouse trials revealed that the combination of DMDS and DZ (30 + 25 g m(-2)) successfully suppressed Meloidogyne spp. root galling, sharply reduced the colony-forming units of Fusarium spp. and Phytophthora spp. on media, maintained high cucumber yields, and was not significantly different from MB or DMDS alone, but better than DZ alone. All of the chemical treatments provided significantly better results than the nontreated control. The results indicate that the combination of DMDS and DZ is an efficient MB alternative for cucumber production.

Development of effective alternative soil fumigants is essential to the phasing out of methyl bromide (MeBr) while keeping major soilborne pathogens under control. Here, we report on the laboratory studies and field trials evaluating methyl iodide (MeI) and chloropicrin (Pic) for control of major soilborne ginger (Zingiber officinale) pathogens Ralstonia solanacearum, Pythium spp., Fusarium oxysporum, and Meloidogyne incognita in Shandong province of China. Laboratory studies indicated that MeI at 24 mg/kg of soil was most effective, reducing four pathogens by >90%. Treatments with MeI+Pic at 12 mg/kg (1:3 and 1:5) also reduced these pathogens by >82%. In the field trials, MeI at 30 or 40 g/m2 and MeI+Pic (1:3) at 40 g/m2 yielded excellent long-term control of all target pathogens. These treatments allowed ginger plants to maintain vigorous growth and produce a greater number of tillers (>12 per plant), and increased ginger yields by >80% compared with the nontreated controls. MeI at a reduced rate of 20 g/m2 or Pic at 40 g/m2 provided levels of disease control similar to MeBr. These studies demonstrated that injection treatments with MeI at 30 and 40 g/m2, and MeI+Pic (1:3) at 40 g/m2, followed by covering with virtually impermeable film, are effective alternatives of soil fumigation for control of the major ginger pathogens in Shandong.

1 BACKGROUND Two soil fumigants, chloropicrin (CP) and dimethyl disulfide (DMDS), were used to control Fusarium wilt disease (FWD) which caused large economic losses in strawberries. The fumigants were evaluated alone and in combination in a laboratory study and in strawberry greenhouses. 2 RESULTS Laboratory tests found that combinations of CP and DMDS indicated a positive synergistic activity on Fusarium oxysporum. A newly developed quantitative assay for F. oxysporum involving real-time PCR was used successfully to evaluate F. oxysporum control by the fumigants; it provided similar results to the selective medium but was less time-consuming and less labor intensive. Greenhouse trials revealed that the combination of CP and DMDS successfully suppressed the incidence of FWD and sharply reduced the population density of F. oxysporum, which significantly increased fruit branch number and maintained a good strawberry yield, higher than methyl bromide (MB) treatment. All of the treatments provided significantly better results than the non-treated control. 3 CONCLUSION This study confirms that the newly developed real-time PCR quantitative assay for F. oxysporum was suitable for the control efficacy evaluation of soil fumigants and that the novel fumigant combination of CP and DMDS offers a promising effective alternative to MB for the control of F. oxysporum in strawberry greenhouses. © 2013 Society of Chemical Industry

Metam-sodium (MS) is widely used as a soil pre-plant fumigant as methyl bromide is phased out of agriculture. However, the information about how fumigation with MS affects the soil microbial community is still limited. In this study, a 66-day-long experiment was conducted to ascertain the effects of MS on soil substrate-induced respiration (SIR), microbial biomass nitrogen (MBN), NH4+-N and NO3--N concentrations, as well as the abundance of the total bacteria and fungi and the expression of genes involved in nitrogen cycling. In addition, 16S rRNA amplicon sequencing was used to investigate the effect of MS on the soil bacterial community. The half-lives of high and low doses of methyl isothiocyanate (MITC) are 10.51h and 9.93h, respectively. MS caused a short-term inhibition of SIR, MBN; had an accumulation effect on NH4+-N concentration in the short term; reduced the abundance of the total bacteria and fungi; and suppressed the expression of the nifH, AOA-amoA, anammox bacteria, nosZ, nirS, and narG. In addition, under the influence of MS, soil bacterial diversity decreased significantly in the long term, bacterial community structure was affected, and there was a shift in the predominant population; for example, some genera, such as Paenibacillus and Luteimonas, significantly increased in number. These changes in bacterial flora may be closely related to the growth of crops. Our study provides useful information for environmental safety assessments of MS in China.

Colletotrichum gloeosporioides is one of the most important pathogens in the world, capable of infecting at least 1,000 kinds of plants (Phoulivong et al. 2010). Mikania micrantha Kunth (Asteraceae), commonly known as mile-a-minute weed, is an extremely fast-growing, perennial creeping weed. Its native distribution is in Central and South America. It has been present in south China since the 1980s and has caused adverse impact on agricultural production in the established area (Li et al. 2013). In 2014, the incidence of anthracnose disease on M. micrantha reached 65 to 90% in Huizhou city, Guangdong, China, and plant mortality up to 45% was observed (Chen et al. 2006). The disease symptoms appeared as brown spots on the leaves and stems of M. micrantha; as the disease progressed, lesions turned dark brown. The location of the disease gradually expanded and even spread throughout the plant (Chen et al. 2006). Thirty symptomatic leaves were sampled from three regions: north of the city (Boluo, 114°28′ E, 23°18′ N), city center (Huidong, 114°72′ E, 22°98′ N), and south of the city (Huiyang, 114°43′ E, 22°80′ N) in Huizhou. Ten pieces from each leaf were surface sterilized with 70% ethanol for 30 s, and then they were rinsed in sterile distilled water and placed on potato dextrose agar (PDA) medium at 27°C in a dark chamber. Colonies grown on medium were round and carpetlike. Aerial hyphae grew more dense, and colonies became gray and black to dark green color. Conidia group showed visible pink and occasionally visible black dots scattered on the surface of the medium. Microscopic spores observed were cylindrical and colorless, 6 to 18 μm in length, and 3 to 5 μm wide. The identification of one representative isolate (H1) was determined by sequencing of the rDNA internal transcribed spacer regions 1 and 2 and the 5.8S using primers (White et al. 1990), and the sequence of each isolate was deposited in GenBank (accession no. KM501061). A BLAST search showed 100% identity with a C. gloeosporioides strain (accession no. KM357285.1). Isolate H1 was also confirmed as C. gloeosporioides with specific primers Colg 1 (5′-AACCCTTTGTGAACATACC-3′) and Colg 2 (5′-CCCTCCGGATCCCAG-3′) (Chen et al. 2006). The pathogenicity test of isolate H1 was carried out in a greenhouse. Ten plants were grown for 20 days in plastic pots (diameter 20 cm) in sandy soil (pH = 5.48) before inoculation. Isolate H1 was grown on PDA medium for 72 h, and the spores were harvested with sterile distilled water. Aqueous spore suspensions of isolate H1 were adjusted with deionized water to 1 × 10⁸ spores/ml and sprayed on the leaves of the plants. All the plants were then placed in the greenhouse at 25 ± 1°C and assessed for disease symptoms. The inoculated isolate caused symptoms identical to those observed in the field, and it was reisolated from the infected leaves and identified as previously described, and none of the untreated plants showed any signs of infection. To our knowledge, this is the first report of anthracnose caused by C. gloeosporioides on M. micrantha in China.

BACKGROUND Root-knot nematodes and soil-borne diseases constrain the rapid development of protected agriculture in China, especially while phasing out methyl bromide (MB). The fumigant sulfuryl fluoride (SF) is currently used as an alternative to MB for the disinfestation of buildings and post-harvest commodities. Our experiments aimed to evaluate a novel application of SF as a soil fumigant in greenhouses in China. RESULTS Dose–response experiments indicated that SF has good efficacy on root-knot nematodes (Meloidogyne spp.) and moderate activity against Fusarium spp. and weeds (Digitaria sanguinalis (L.) Scop. and Abutilon theophrasti Medicus). The field trials indicates that SF has good efficacy, between 80 and 94%, on Meloidogyne spp., and Fusarium spp. at the rates of 25–50 g m−2 in tomato and cucumber in Beijing and Shandong Province. Marketable yield and plant vigour was not significantly different in SF and MB treatments. SF has lower emissions than MB during the fumigation operation. It is simple to apply, can be used at low temperature, and has a short plant-back time. SF was found to be an economically feasible alternative to MB for nematode control in China. CONCLUSION SF can be used as a soil fumigant to control root-knot nematodes and to reduce the levels of key soil pathogens. © 2013 Society of Chemical Industry

A gelatin capsule (gel cap) formulation of the mixture of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) has been developed to reduce environmental emissions and potential human exposure from the use of 1,3-D/CP as a soil fumigant. The objective of the present study was to evaluate the biological efficacy of 1,3-D/CP gel cap formulations under greenhouse trial conditions. The current results indicate that a 1,3-D/CP gel cap formulation at 30 or 50 g a.i. m −2 can reduce the soil populations of Fusarium spp., Phytophthora spp., Pythium spp. and Meloidogyne spp.. In all tested crops, the 1,3-D/CP gel cap formulation provided marketable yields that were significantly higher than untreated controls and equal to the methyl bromide and 1,3-D/CP liquid injection treatments. Yields of tomato and a subsequent melon crop in plots treated with 1,3-D/CP gel cap were 93% and 87% greater, respectively, than the control. The yields of grafted cucumber and the subsequent balsam pear crop were increased by 16% and 201% respectively, compared to the control. The present study confirms that the tested 1,3-D/CP gel cap formulation provides a promising method for soil pest and disease control and reducing environmental emissions and potential human exposure in greenhouse vegetable cultivation.

Soil fumigation has significant effects on nitrification. Better quantification of soil nitrification after fumigation can benefit fertilizer recommendation.The effects of methyl bromide (MB), sulfuryl fluoride (SF), methyl iodide (MI), metham sodium (MS) and chloroform (CF) fumigation on soil nitrification dynamics were evaluated in laboratory incubation. After removal of the fumigant, the soils were incubated at 25°C in aerobic conditions for 20 weeks. An accumulation of soil ammonium-nitrogen ( -N) content was found after MB, MI, MS and CF fumigation compared to untreated control at 1 and 2 WAF (weeks after fumigation). Soil -N accumulation lasted up to 4 WAF in MI treatment. Fumigants also increased soil dissolved amino acids (DAA) significantly except for SF at 1 WAF. The levels of microbial biomass nitrogen (MBN) in all fumigated treatments were lower than the levels in the untreated control at 1 WAF and potential nitrification rates in all five fumigant treatments were significantly lower than in t...

Chloropicrin retards the conversion of ammonia to nitrite during the nitrification process in soil. In our study, the dynamic effect of chloropicrin fumigation on soil nitrification was evaluated in five different soil types to identify relationships between soil properties and the effect of fumigation on nitrification. Chloropicrin significantly inhibited nitrification in all soils; however, the recovery of nitrification varied greatly between the soils. Following chloropicrin fumigation, nitrification recovered to the control level in all soils, except in the acidic Guangxi soil. Nitrification recovered faster in fumigated sandy loam Beijing soil than in the other four fumigated soils. Soil texture and pH were two important factors that influenced chloropicrin's inhibitory effect on nitrification. An S-shaped function was fitted to soil NO3--N content to assess the nitrification recovery tendency in different soils. The time taken to reach maximum nitrification (tmax) ranged from 2.4 to 3.0 weeks in all unfumigated soils. Results demonstrated that tmax was greater in all fumigated soils than in untreated soils. Correlation calculations showed that tmax was strongly correlated to soil texture. The correlation analysis results indicated that the recovery rate of nitrification after chloropicrin fumigation is much faster in sandy loam soil than silty loam soil.

Oils extracted from the leaves of Eupatorium adenophorum were tested in vitro and in vivo against the soilborne pathogen Pythium myriotylum which causes soft rot, a devastating disease of commercial ginger production in China. Twelve compounds accounting for 99.15% of the total oil composition were identified by GC-MS. The major components were 10Hβ-9-oxo-agerophorone (37.03%), 10Hα-9-oxo-agerophorone (37.73%) and 9-oxo-10, 11-dehydro-agerophorone (23.41%). Antifungal activity was tested by the poisoned food technique against P. myriotylum, indicating minimum inhibitory concentrations of 100μg/ml after 7 days incubation. In addition, the oil extracts greatly inhibited the formation of both wet and dry mycelial biomass. The combination of E. adenophorum oil extracts and synthetic fungicides showed a strong synergistic effect, inhibiting the mycelial growth in in vitro assays. The synergistic effect of oil extracts with fungicides could allow fungicides to be used at reduced rates in the future which has environmental advantages. Oil extracts applied at 160 and 200μg/ml concentrations to ginger rhizomes before inoculation with P. myriotylum significantly reduced the infection rate in ginger. Examination by light and transmission electron microscopy revealed that oil extracts caused swelling of the hyphae, disruption of the cell wall, degradation of the cytoplasmic organelles and shortening of the cytoplasmic inclusion. These results suggested that the plasma membrane and endomembrane systems of P. myriotylum were severely damaged by the oil extracts of E. adenophorum which offer significant potential for use as a fungicide to control P. myriotylum.

Biochar can potentially reduce fumigant emissions in agriculture. Dimethyl disulfide (DMDS) is an effective soil fumigant for controlling soil-borne pests. However, it is important to reduce DMDS emissions because the compound has an unpleasant and easily perceived sulfur odor. This study therefore aimed to determine the effects of two types of biochar amendments on DMDS bioactivity and emission, using bioassay methods and soil columns. The efficacy of DMDS for controlling root-knot nematode and Fusarium spp. was not reduced when the biochar used in this study was applied at a rate less than 2 and 0.5 % (on a weight basis), respectively. The biochar with high specific surface area (SSA 113 m−2 g−1) reduced the efficacy of DMDS against soil-borne pests more than the low SSA biochar (14 m−2 g−1). Increased doses of DMDS were able to offset decreases in the efficacy of DMDS in soils amended with biochars, except for high SSA biochar applied at a rate of 2 %. Biochar amendments applied to the soil surface at shallow depth can significantly reduce DMDS emission to the atmosphere. The results of this study will support decision-making about the practical use of biochar to reduce DMDS emissions.

Gelatin capsules containing chloropicrin (Pic gel cap) were developed as a new formulation to reduce the potential human exposure risks associated with injection application methods. The objective of this study was to test the efficacy of a Pic gel cap formulation on soilborne pathogens and to determine the effects on strawberry plant growth and fruit yield. Three field experiments were conducted in strawberry greenhouses located in Mancheng County, China, in 2008-2010. The results demonstrated that effects of Pic gel cap on soilborne pathogens were similar to Pic injection; Pic gel cap effectively reduced key soilborne pathogens population, was partially effective against weeds, improved strawberry plant growth, and increased fruit yield significantly compared to the untreated control. Pic gel cap applied to preformed beds uses less fumigant than broadcast applications of Pic gel cap and can provide an equivalent level of disease control. The present study confirms that the Pic gel cap is a promising new formulation which provides field efficacy and marketable yields similar to Pic injection or methyl bromide in strawberry cultivation in China.

Background Root-knot nematode (Meloidogyne spp., RKN) causes a disease that significantly reduces the yield of greenhouse cucumber crops year after year. Chemical control based on a single pesticide is now unreliable mainly due to pest resistance. Fumigant and non-fumigant pesticide combinations can potentially result in effective and economic RKN control. Results Combining the insecticide abamectin (ABM) with fumigants dazomet (DZ) or chloropicrin (CP) significantly extended the half-life of ABM by an average of about 1.68 and 1.56 times respectively in laboratory trials, and by an average of about 2.02 and 1.69 times respectively in greenhouse trials. Laboratory experiments indicated that all the low rate ABM combination treatments controlled RKN through a synergistic effect. ABM diffused into the nematode epidermis more rapidly when ABM was combined with DZ and CP, giving effective nematode control and an increase cucumber total yield, compared to the use of these products alone. ABM combined with CP or DZ produced significantly higher total cucumber yield than when these products were used alone. Conclusions A low concentration of ABM combined with DZ in preference to CP would be an economic and practical way to control nematode and soilborne fungi in a greenhouse producing cucumbers.

The gelatin capsule (gel cap) formulation of 1,3-dichloropropene (1,3-D) was developed as a potential means of reducing 1,3-D emissions. The objective of this study was to determine the distribution, emission, and leaching of 1,3-D after applying the gel cap in soil columns. Comparable 1,3-D soil gas concentrations were obtained between a conventional liquid injection control and the gel cap application with film treatment. When the soil surface was irrigated with 39.6 mm water per day during the first 4 days, 1,3-D soil gas concentration was higher than the film treatments at depths below 20 cm, but lower concentrations were observed at 0-15 cm depth. The application of 1,3-D gel cap relatively reduced total 1,3-D emission by about 41% compared to liquid injection with film cover, and total 1,3-D emission was only 0.13% for 1,3-D gel cap application with 4 days of irrigation without a tarp. The results indicated that 1,3-D gel cap could be a promising new technology for reducing environmental emissions and potential human exposure.

The gelatin capsule (gel cap) formulation of 1,3-dichloropropene (1,3-D) is a new concept to reduce the environmental release, transport, and hazard potential of the use of 1,3-D to control soilborne diseases and nematodes. The objective of this study is to evaluate the biological efficacy of the 1,3-D gel cap formulation under laboratory and greenhouse trial conditions. Greenhouse experiments were carried out in suburbs of Beijing and Hebei Province of China in 2007 and 2008, focused mainly on tomato and Bellis perennis L. (daisy) crops. Results showed that 1,3-D gel cap application at a rate of 16.8 g of active ingredient m(-2) was as effective as 1,3-D liquid injection treatment. Crop yields in plots treated with 1,3-D gel cap and 1,3-D liquid were significantly higher than those in untreated control. The present study confirms that the 1,3-D gel cap formulation is a promising new formulation with good field efficacy.

Soil fumigation is an important treatment in the production chain of fruit and vegetable crops, but fumigant emissions contribute to air pollution. Biochar as a soil amendment has shown the potential to reduce organic pollutants, including pesticides, in soils through adsorption and other physicochemical reactions. A laboratory column study was performed to determine the effects of soil applications of biochar for reducing emissions of the fumigant 1,3-dichloropropene (1,3-D). The experimental treatments comprised of unamended and amended with biochar at doses of 0, 0.5, 1, 2, and 5% (w/w) in the top 5 cm soil layer. The unamended treatment resulted in the highest emission peak flux at 48 to 66 μg m s. Among the biochar amendment treatments, the highest peak flux (0.83 μg m s) was found in the biochar 0.5% treatment. The total emission loss was 35.7 to 40.2% of applied for the unamended treatment and0.1 to 2.9% for the biochar-amendment treatments. A germination bioassay with cucumber seeds showed that ≥7 d of aeration would be needed to avoid phytotoxicity before replanting in biochar-containing fumigated soil. The results indicate that treatments with 0.5% or more biochar amendment reduced emission peak flux by99.8% and showed total 1,3-D emission loss by92% compared with that without biochar. The amendment of surface soil with biochar shows a great potential for reducing fumigant emissions.

Eupatorium adenophorum Spreng., a major invasive weed in southwestern China, has caused great economic losses. In order to find a new herbicide to control E. adenophorum, experiments were conducted to study its physiological and biochemical responses to low and high doses of picloram herbicide (4-amino-3,5,6-trichloropyridine-2-carboxylic acid). Electrolyte leakage, malondialdehyde, and free proline were stimulated by picloram, showing a remarkably increase (p < 0.05) with high herbicide concentration (60, 120, and 240 g ai ha-1). The treated plants exhibited lower osmotic adjustment capacity, high dosage lipid peroxide levels and more free-proline accumulation. It was found that low doses (12 and 24 g ai ha-1) of picloram initially increased catalase, peroxidase, superoxide dismutases and protein, but these indicators decreased (p < 0.05) with the increase of treating time (after 3 d) and dose (120 and 240 g ai ha-1). In addition, the structures of chloroplasts and mitochondria were seriously deformed. These results indicated E. adenophorum can improve its herbicide-tolerance by increasing the antioxidative system activity at the initial period of low picloram stress. However, this protective function disappeared with increasing of treating time and picloram dosage. Eupatorium adenophorum responded differently to low and high concentrations of picloram and ultrastructural changes are an important cause of death in E. adenophorum.

Methyl bromide (MB) and other alternatives were evaluated for suppression of Fusarium spp., Phytophthora spp., and Meloidogyne spp. and their influence on soil microbial communities. Both Fusarium spp. and Phytophthora spp. were significantly reduced by the MB (30.74 mg kg-1), methyl iodide (MI: 45.58 mg kg-1), metham sodium (MS: 53.92 mg kg-1) treatments. MS exhibited comparable effectiveness to MB in controlling Meloidogyne spp. and total nematodes, followed by MI at the tested rate. By contrast, sulfuryl fluoride (SF: 33.04 mg kg-1) and chloroform (CF: 23.68 mg kg-1) showed low efficacy in controlling Fusarium spp., Phytophthora spp., and Meloidogyne spp. MB, MI and MS significantly lowered the abundance of different microbial populations and microbial biomass in soil, whereas SF and CF had limited influence on them compared with the control. Diversity indices in Biolog studies decreased in response to fumigation, but no significant difference was found among treatments in PLFA studies. Principal component and cluster analyses of Biolog and PLFA data sets revealed that MB and MI treatments greatly influenced the soil microbial community functional and structural diversity compared with SF treatment. These results suggest that fumigants with high effectiveness in suppressing soil-borne disease could significantly influence soil microbial community.

Background Chloropicrin (Pic) offers a potential alternative to methyl bromide (MB) against Ralstonia solanacarum in ginger (Zingiber officinale Rosc.) production. MB is scheduled to be withdrawn from routine use by 2015 in developing countries. Methods Pic treatments were evaluated in a laboratory study and in three commercial ginger fields. Results Laboratory studies showed that the EC50 value and EC80 value of Pic were 2.7 and 3.7 mg a.i. kg−1 soil, respectively. Field trials in highly infested soil revealed that treatments of Pic at the dose of 50 g m−2 covered with totally impermeable film (TIF) or polyethylene film (PE) sharply reduced Ralstonia solanacarum and maintained high ginger yields. Both of the Pic treatments provided results similar to, or in some cases slightly lower than, MB with respect to Ralstonia solanacarum control, plant survival, plant growth and yield. All of the fumigant treatments were significantly better than the non-treated control. Conclusions The present study confirms that the Pic is a promising alternative with good efficacy against Ralstonia solanacarum for ginger production and could be used in integrated pest management programs in China.