The control of agricultural pests is key to maintain economically viable crops. Increasing environmental awareness, however, is leading to more restrictive European policies regulating the use of certain pesticides due to their impact on human health and the soil system. Given this context, we evaluated the efficacy of three alternatives to the soil fumigant 1,3-dichloropropene (1,3-D), which is currently banned in Europe: two non-fumigant nematicides [oxamyl (OX) and fenamiphos (FEN)] and the soil fumigant dimethyl disulfide (DMDS). We analysed the efficiency of these pesticides against root-knot nematodes and soil fungal pathogens (determined by qPCR) as well as the soil biological quality after treatments application (estimated by enzyme activities). Among treatments, 1,3-D and DMDS significantly reduced nematode populations. FEN was more effective in sandy soil, while OX had no effect in any soil. OX and FEN had no effect on fungal pathogens, whereas DMDS reduced the abundance of Rhizoctonia solani and Fusarium solani at the root level in clay-loam soil. Soil quality decreased after treatment application but then recovered throughout the experiment, indicating the possible dissipation of the pesticides. Our findings support DMDS as a potential sustainable alternative for controlling root-knot nematodes and fungal pathogens due to its effectiveness in both studied soils, although its negative impact on soil biological quality in sandier soils must be taken into account.Main finding of the work. DMDS is a reliable alternative to 1,3-D for controlling agricultural pest but its inhibitory effect on soil enzyme activities varied according to the soil characteristics.

Invasive plants readily invade metal-contaminated areas. The hyperaccumulation of toxic heavy metals is not an uncommon feature among plant species. Although several hypotheses were proposed to explain this phenomenon, it is currently unclear how hyperaccumulation may benefit plants. The invasive Crofton weed (Ageratina adenophora) is a known hyperaccumulator of chromium and lead. We previously found that the species can also hyperaccumulate cadmium. The role of phytoaccumulation in defense to pathogen attack is unclear. We inoculated A. adenophora plants with a common generalist pathogen (Rhizoctonia solani) to test its resistance under cadmium treatment. We found evidence that cadmium hyperaccumulation reduced pathogen infection in A. adenophora. Our findings indicate elemental defense is highly cost efficient for hyperaccumulators inhabiting metal-contaminated sites, where plants were only modestly affected by cadmium. The reduction in pathogen damage conferred by cadmium was relatively high, particularly under lower cadmium levels. However, the benefits at higher levels may be capped. Elemental defense may be a key mechanism for plant invasion into polluted sites, especially in regions with widespread industrial activity. Our study highlights the importance of testing different metal concentrations when testing plant resistance and the importance of considering enemy attack when selecting plants for phytoremediation.

Thifluzamide fungicide is widely used to protect rice (Oryza sativa) against the sheath blight fungus (Rhizoctonia solani). The continuous application of thifluzamide may lead to accumulation in soil and contaminate rice crop. To sustain the environment, it is necessary to assess its accumulation and degradation in field. The method limit of detection (LOD) was 0.022 ng. The limits of quantitation detection (LOQ) were 5.0 μg L⁻¹in water and 4.0 μg kg⁻¹in paddy soil and rice crop. In this study, a 2-year (2011–2012) field study was performed to monitor thifluzamide degradation in the rice production areas of Nanjing, Xiaoxian, and Changsha. The degradation dynamics of thifluzamide in paddy water, paddy soil, and rice crop were well described by the first-order kinetics equation. The 2-year average half-lives of thifluzamide in paddy water, paddy soil, and rice crop were 26.19, 17.92, 14.61 days (Nanjing), 15.63, 20.71, 9.10 days (Xiaoxian), and 9.47, 13.92, 10.08 days (Changsha), respectively. Thifluzamide degraded more rapidly in rice crop than in soil and paddy water. The variation in thifluzamide degradation was attributed to the difference in rainfall during the period of rice cultivation. The maximum residue of thifluzamide in brown rice was 0.0303 mg kg⁻¹in Nanjing and the residue of thifluzamide in brown rice was not detected in other two sites before thifluzamide was applied at pre-harvest. The experimental data demonstrated that thifluzamide recommended dosage of 72 g a.i.ha⁻¹can be used in rice fields with less than three times within a 30-day time interval.

The development of mixed microbial agents can reduce the use of pesticides and fertilizers in agriculture. However, most previous studies focused only on the overall effects of mixed microbial agents and ignored the interactions between bacteria in mixed systems. In this study, Bacillus subtilis SL-44 and Enterobacter cloacae Rs-2 were used to explore the interactions between two different functional plant growth-promoting rhizobacteria (PGPR). The plant growth-promotion properties and inhibition rate of Rhizoctonia solani were determined, and the mechanism of the interactions under single and co-culture conditions was elucidated via transcriptomics analysis under single and co-culture conditions. Results showed that the co-culture was not conducive to B. subtilis SL-44 growth. Furthermore, the differentially expressed genes related to B. subtilis SL-44 developmental process and cell differentiation were downregulated by 82.7% and 84.8% respectively. Moreover, among the properties, only siderophore production by the mixed culture was higher than that of single cultures because of the upregulation of the siderophore-related genes of B. subtilis SL-44. In addition, results revealed the altruistic relationship between the two strains, and the chemical and non-chemical signals of their interaction. This study provides unique insights into PGPR interactions and offers guidance for the development and application of mixed microbial agents.

Green synthesis of silver nano-particles (AgNPs) from silver nitrate was carried out using purple-colored rice leaves’ extracts containing higher phenols, anthocyanins, and flavonoids. The efficacy of synthesized AgNPs was tested against rice diseases and investigation was carried out to check negative effect of AgNPs on soil microbes. Substantial reduction of total anthocyanins, total phenols, and total flavonoids was observed in reaction mixture during AgNP formation indicating the role of secondary metabolites on AgNP formation and stabilization. Scanning electron microscopy coupled with energy-dispersive spectroscopic images and FTIR spectral analysis of AgNPs confirmed the presence of elemental silver encapped by biomolecules. The optimized reaction parameters for synthesis of AgNPs from silver nitrate were (a) 48 h of incubation, (b) 9:1 (v/v) 1 mM AgNO3:plant extract, and (c) room temperature at 20–30 °C. Zeta potential and hydrodynamic particle sizes of synthesized AgNPs were ranged between − 16.61 to − 29.45 mV and 36–107 nm, respectively, at different time of incubation. AgNPs could control effectively Rhizoctonia solani and Xanthomonas oryzae pv. Oryzae and Helminthosporium oryzae. AgNPs at higher concentration could cause negative effect on microbial biomass carbon and soil enzymes for distant future. But the negative effects of AgNP solution (10% of 1 mM AgNPs) were comparable to commercial fungicide, carbendazim. The synthesized AgNPs with desirable characters were effective against a number of disease-causing pathogens in rice, and it can be recommended as broad-spectrum pesticide.

Introduction Chlorimuron-ethyl has been widely used for the soybean production of China, but less information is available on the possible risk of long-term application of this herbicide. Materials and methods In this paper, soil samples were collected from the plots having been received 30 g active component of chlorimuron-ethyl/ha per year for 5 and 10 years in a continuously cropped soybean field of Northeast China, with their microbial community analyzed by plate counting, PCR-DGGE, and cloning library. Chlorimuron-ethyl had a higher accumulation in test soils, and the accumulation decreased the CFU of soil bacteria and increased the CFU of soil fungi significantly. The CFU of soil actinomycetes only had a significant decrease in the plot having been received chlorimuron-ethyl for 10 years. Results and discussion Under the long-term stress of chlorimuron-ethyl, the diversity and evenness of soil microbial community decreased, and more importantly, some bacterial and fungal species that possibly benefited soybean's growth, e.g., Acidobacteria, γ-proteobacteria, Cortinarius violaceu, Acarospora smaragdula, and Xerocomus chrysenteron decreased or demised, while some species that could induce the obstacle of soybean's continuous cropping, e.g., Fusarium oxysporum, Rhizoctonia solani, and Phytophthora sojae, increased or appeared. Some actinomycetes were inhibited having negative effects on the antagonism between soil microbes. It is considered that due to the longer half-life of chlorimuron-ethyl in soil and the resistance and resilience of soil microbes to short-term environmental stress, long-term in situ investigation rather than laboratory microcosm test or short-term field experiment would be more appropriate to the accurate assessment of the ecological risk of long-term chlorimuron-ethyl application. Further studies should be made on the application mode and duration of chlorimuron-ethyl to reduce the possible ecological risk of applying this herbicide on continuously cropped soybean field.

This study reports the potential of a soil bacterium, Bacillus subtilis strain SPB1, to produce lipopeptide biosurfactants. Firstly, the crude lipopeptide mixture was tested for its inhibitory activity against phytopathogenic fungi. A minimal inhibitory concentration (MIC), an inhibitory concentration at 50 % (IC50 %), and an inhibitory concentration at 90 % (IC90 %) values were determined to be 0.04, 0.012, and 0.02 mg/ml, respectively, for Rhizoctonia bataticola with a fungistatic mode of action. For Rhizoctonia solani, a MIC, an IC50 %, and IC90 % values were determined to be 4, 0.25, and 3.3 mg/ml, respectively, with a fungicidal mode of action. For both of the fungi, a loss of sclerotial integrity, granulation and fragmentation of hyphal mycelia, followed by hyphal shriveling and cell lysis were observed with the treatment with SPB1 biosurfactant fraction. After extraction, separation, and purification, different lipopeptide compounds were identified in the culture filtrate of strain SPB1. Mass spectroscopic analysis confirmed the presence of different lipopeptide compounds consisting of surfactin isoforms with molecular weights of 1007, 1021, and 1035 Da; iturin isoforms with molecular weights of 1028, 1042, and 1056 Da; and fengycin isoforms with molecular weights of 1432 and 1446 Da. Two new clusters of lipopeptide isoforms with molecular weights of 1410 and 1424 Da and 973 and 987 Da, respectively, were also detected. This study reported the ability of a B. subtilis strain to co-produce lipopeptide isoforms with potential use as antifungal compounds.