Lentinan protects Caenorhabditis elegans against fluopyram-induced toxicity through DAF-16 and SKN-1 pathways.

Fluopyram, a SDH inhibitor fungicide, is widely used in agriculture to control fungi and nematodes. However, fluopyram has been proved toxic that caused damage to organs through oxidative stress. The development of natural extracts that can reduce oxidative damage is a promising method. Lentinan is isolated from Lentinus edodes and has been verified its antioxidant activity. In this study, Caenorhabditis elegans was used to evaluate the protective effects of lentinan against fluopyram-induced toxicity and the possible mechanisms. Results showed that lentinan pretreatment notably increased the survival rate of N2 nematodes by 15.0 % and extended the lifespan by 91.5 %, compared with the fluopyram treatment. Lentinan pretreatment reverted the inhibition of the locomotion and reproduction of C. elegans under the fluopyram stress. In addition, lentinan pretreatment significantly decreased the contents of ROS and MDA in N2 nematodes. Moreover, pretreated with lentinan significantly recovered the decreased activities of CAT, SOD, GST and SDH induced by fluopyram. Lentinan pretreatment enhanced the mRNA levels of daf-16 and skn-1 and their downstream genes in the nematodes compared with the fluopyram group. In daf-16 and skn-1 mutants, the lifespan, ROS and related genes expression were not significantly changed in lentinan pretreatment. Pretreated with lentinan significantly enhanced the fluorescence intensity of SOD-3::GFP and GST-4::GFP, and promoted the nuclear translocation of DAF-16 and SKN-1 under the fluopyram stress. In summary, these findings indicated that lentinan protected C. elegans from fluopyram-induced toxicity via DAF-16 and SKN-1.

Oxidative stress and mitochondrial damage induced by a novel pesticide fluopimomide in Caenorhabditis elegans.

Fluopimomide is a novel pesticide intensively used in agricultural pest control; however, its excessive use may have toxicological effects on non-target organisms. In this study, Caenorhabditis elegans was used to evaluate the toxic effects of fluopimomide and its possible mechanisms. The effects of fluopimomide on the growth, pharyngeal pumping, and antioxidant systems of C. elegans were determined. Furthermore, the gene expression levels associated with mitochondria in the nematodes were also investigated. Results indicated that fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.001) decreased body length, pharyngeal pumping, and body bends in the nematodes compared to the untreated control. Additionally, fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.05) increased the content of malondialdehyde by 3.30-, 21.24-, and 33.57-fold, respectively, while fluopimomide at 1.0 and 5.0 mg/L significantly (p < 0.001) increased the levels of reactive oxygen species (ROS) by 49.14% and 77.06% compared to the untreated control. In contrast, fluopimomide at 1.0 and 5.0 mg/L notably reduced the activities of target enzyme succinate dehydrogenase and at 5.0 mg/L reduced the activities of antioxidant enzyme superoxide dismutase. Further evidence revealed that fluopimomide at 1.0 and 5.0 mg/L significantly inhibited oxygen consumption and at 0.2, 1.0, and 5.0 mg/L significantly inhibited ATP level in comparison to the untreated control. The expression of genes related to the mitochondrial electron transport chain mev-1 and isp-1 was significantly downregulated. ROS levels in the mev-1 and isp-1 mutants after fluopimomide treatments did not change significantly compared with the untreated mutants, suggesting that mev-1 and isp-1 may play critical roles in the toxicity induced by fluopimomide. Overall, the results demonstrate that oxidative stress and mitochondrial damage may be involved in toxicity of fluopimomide in C. elegans.

Biocontrol Efficacy of Bacillus methylotrophicus TA-1 Against Meloidogyne incognita in Tomato.

Root-knot nematodes (RKNs) are harmful plant-parasitic nematodes of tomatoes which can cause significant yield losses. Therefore, there is increasing interest in exploring the application of bacterial nematicides. The bacterium Bacillus methylotrophicus TA-1 is a broad-spectrum biological control agent; however, its effect on RKNs control remains largely unclear. In this study, the toxicity of B. methylotrophicus TA-1 against Meloidogyne incognita was investigated in vitro, and the potential of B. methylotrophicus TA-1 to decrease infection of RKNs in tomato were evaluated in pot and field trials. Results showed that B. methylotrophicus TA-1 exhibited high nematicidal activity against second-stage juveniles (J2s) and eggs of M. incognita with 50% lethal concentration (LC50) values of 5.80 and 7.00 × 108 colony forming units (CFU)/ml, respectively. In the pot experiments and field trials conducted in 2020 and 2021, tomato plants treated with B. methylotrophicus TA-1 soil drench applied once at 3, 6, and 9 × 108 CFU/plant had significantly higher plant height and greater yield compared with the untreated control. Tomato yields of the treated plots with B. methylotrophicus TA-1 in 2 consecutive years' field trials were between 53.4 to 66.1 and 52.8 to 61.5 t/ha, while they were 49.7 and 48.2 t/ha in the untreated control for each year, respectively. The lowest population densities of M. incognita at 30 and 60 days after treatment were 119 and 135 J2s per 100 g soil in 2020 and 43 and 118 J2s in 2021 in TA-1-treated plots. The lowest gall index of 4.7 and 3.3 in 2020 and 2021, respectively, and the highest yield were all observed in the TA-1 at 9 × 108 CFU/plant treated plants, with no significant differences with the commercial control abamectin. These results provided a basis for further studies of B. methylotrophicus TA-1 formulations, application doses, frequencies, and mechanisms of action, which are necessary before it could be used as a component of integrated management programs to manage RKNs in tomato production.

Long-term antibacterial, antioxidative, and bioadhesive hydrogel wound dressing for infected wound healing applications.

Bacterial infection and oxidative stress hinder clinical wound healing. Therefore, wound dressings with antibacterial and antioxidative properties are urgently needed. In this study, a type of quaternized lignin (QL) functionalized poly(hexamethylene biguanide) hydrochloride (PHMB) complex incorporated polyacrylamide (QL-PHMB-PAM) hydrogel was developed as a multifunctional dressing material for the promotion of infected wound repair. Owing to the abundant catechol groups of quaternized lignin, the QL-PHMB-PAM hydrogel exhibited robust repeatable adhesiveness to various substrates with antioxidative properties. Additionally, the antibacterial components of PHMB in the QL-PHMB-PAM composite hydrogel showed high efficiency and long-term antibacterial activity against Staphylococcus aureus (S.aureus), Escherichia coli (E.coli), and methicillin-resistant S. aureus (MRSA; up to 100%). Furthermore, in vivo experiments indicated that this multifunctional hydrogel accelerated the healing of S. aureus-infected wounds by promoting the reconstruction of blood vessels and hair follicles. These results demonstrate that this antioxidative, antibacterial, and bioadhesive hydrogel is a promising alternative wound dressing material for the prevention of bacterial infections and the acceleration of infected wound regeneration.

Zwitterionic betaines over HEPES as the new generation biocompatible pH buffers for cell culture.

Good's buffers have been widely applied in cell/organ culture over the past half a century as biocompatible pH stabilizers. However, the emergence of severe adverse effects, such as cellular uptake, lysosomal autophagic activation, and visible light-induced cytotoxicity, raises serious questions over its biocompatibility while underlying mechanism was unclear. Here we report that riboflavin (RF, component of cell culture medium) generates 1O2, ·OH, and O2 •- under visible light exposure during regular cell manipulation. These short half-life reactive oxygen species (ROS) react with tertiary amine groups of HEPES, producing 106.6 µM of H2O2. Orders of magnitude elevated half-life of ROS in the medium caused severe cytotoxicity and systematic disorder of normal cell functions. We have further designed and validated zwitterionic betaines as the new generation biocompatible organic pH buffers, which is able to completely avoid the adverse effects that found on HEPES and derivate Good's buffers. These findings may also open a new avenue for zwitterionic betaine based materials for biomedical applications.

Photonics millimeter wave bidirectional full-duplex communication based on polarization multiplexing.

We have proposed and experimentally implemented a photonics-aided large-capacity long-distance mm-wave bidirectional full-duplex communication system at the W-band based on polarization multiplexing. The same radio frequency (RF) carrier source is shared by both the uplink and the downlink, and a pair of orthomode transducers (OMTs) are used to separate the dual orthogonally polarized channels. To achieve the maximum spectrum efficiency and throughput, 10-Gbaud probabilistically shaped 256-level quadrature-amplitude-modulation (PS-256QAM) signals with 7.07 bit/symbol/Hz are transmitted in Ch. H and Ch. V. The system can support the bidirectional transmission with 103-Gbps data rate over 4600-m RF wireless distance. To the best of our knowledge, based on a photonics-aided bidirectional full-duplex system, this is the first time to realize a record-breaking bit rate-distance product at the W-band, i.e., 103 Gbps × 4.6 km = 473.8 Gbps•km.

Layer-by-layer construction of zwitterionic/biguanide polymers on silicone rubber as an antifouling and bactericidal coating.

Biofilm formation on biomedical devices is a major cause of device-associated infection. Traditional antibiotic treatment for biofilm-associated infection increases the risk of multidrug resistance. Thus, there is an urgent need to develop antibiotic-free strategies to prevent biofilm formation on biomedical devices. Herein, we report a layer-by-layer strategy to construct an antifouling and bactericidal dual-functional coating for silicone rubber (SR)-based substrates. Five zwitterionic active ester copolymers, p(SBMA-co-NHSMA), with varied zwitterionic pSBMA components that ranged from 50 to 90% (molar ratio) were precisely prepared. Based on -NH2/NHS chemistry, a zwitterionic pSBMA antifouling coating was successfully constructed on an -NH2-activated SR surface, while a biguanide polymer (PHMB) bactericidal coating was consequently tethered. The relationship between the composition of the polymeric coating and the overall antibacterial property (antifouling and bactericidal) that was endowed to the SR surface was established. The in vitro and in vivo results consistently showed that the optimal p(SBMA-co-NHSMA) copolymer (SBMA/NHSMA with molar percentage of 70/30) synergistically utilized antifouling and bactericidal abilities to endow a highly efficient overall antibacterial property (near 100% antibacterial ratios) to SR70-PHMB substrates without compromising cellular viability. This strategy may be applied to the many SR-based biomedical implants and devices where an antibacterial surface is required.

Exposure to fluopimomide at sublethal doses causes oxidative stress in Caenorhabditis elegans regulated by insulin/insulin-like growth factor 1-like signaling pathway.

Fluopimomide is an innovative pesticide, widely used for agricultural pest management; however, little is known about its effect on non-target organisms. This study was designed to assess the potential risk of fluopimomide and the molecular mechanisms using Caenorhabditis elegans, a common model animal. The oxidative stress-related indicators were analyzed in C. elegans after exposure to fluopimomide for 24 h at three sublethal doses (0.2, 1.0, and 5.0 mg/L). The results demonstrated that sublethal exposure to fluopimomide adversely affected the nematodes growth, locomotive behaviors, reproduction, and lifespan, accompanying with enhanced of reactive oxygen species (ROS) generation, lipid and lipofuscin accumulation, and malondialdehyde content. In addition, exposure to fluopimomide significantly inhibited antioxidant systems including superoxide dismutase, catalase, glutathione S-transferase, and glutathione in the nematodes. Moreover, the expression of oxidative stress-related genes of sod-3, hsp-16.1, gst-4, ctl-2, daf-16, and daf-2 were significantly down-regulated, while the expression of skn-1 was significantly up-regulated. Further evidence revealed that daf-16 and skn-1 mutant strains of C. elegans significantly decreased ROS production upon fluopimomide exposure compared with the wild-type nematodes. Overall, our findings indicated that exposure to fluopimomide at sublethal doses caused oxidative damage, mainly associated with insulin/IGF-1-like signaling pathway in C. elegans. This is the first report of potential toxic effects of fluopimomide even at low concentrations, providing a new insight into the mechanisms of toxicity to C. elegans by fluopimomide.

Lentinan extends lifespan and increases oxidative stress resistance through DAF-16 and SKN-1 pathways in Caenorhabditis elegans.

Lentinan, extracted from Lentinus edodes, exhibits bioactive properties in vitro; however, little is known about the antioxidant potential in vivo. In this study, the effects of lentinan at 0.05, 0.25 and 1.25 mg/mL on the lifespan, locomotion, reproductive capacity, and oxidative stress resistance in Caenorhabditis elegans were determined. Compared to the untreated control, lentinan at 0.05, 0.25 and 1.25 mg/mL significantly prolonged the lifespan by 17.6%, 35.3% and 25.3% (p < 0.001), respectively, and improved the brood size, locomotion and stress resistance of the nematodes. Furthermore, lentinan at 0.25 mg/mL significantly reduced accumulation of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) by 38.1% (p = 0.013) and 49.7% (p = 0.028), respectively. In addition, lentinan at all tested concentrations significantly increased the activities of superoxide dismutase (SOD) and catalase (CAT). The expression of skn-1 and daf-16 in the treatments with lentinan at 0.25 and 1.25 mg/mL was significantly (p < 0.005) up-regulated compared with the untreated control, whereas that of the daf-2 gene was significantly down-regulated. Further evidence revealed that ROS production in lentinan-treated daf-16 and skn-1 mutant strains was similar to the untreated control. Consistent with the aforementioned results, lentinan enhanced the nuclear translocation of DAF-16 and SKN-1. Our results demonstrated that lentinan could increase lifespan and protect the nematodes from oxidative stress through DAF-16 and SKN-1.

Management of Meloidogyne incognita on Cucumber with a New Nonfumigant Nematicide Fluopimomide.

Cucumber (Cucumis sativus L.) is an economically important vegetable crop in China. Southern root-knot nematode (Meloidogyne incognita) is a significant obstacle in cucumber production, causing severe root damage and yield losses. Moreover, resistance development to fosthiazate, and poor mobility of abamectin, have led to failure to control this nematode. It is of great interest to growers and the vegetable industry to explore novel nonfumigant nematicides that can provide adequate control in an environmentally friendly manner. Fluopimomide (FM), a new chemical having a similar structure to fluopyram, was shown to exhibit toxic effects on fungi and nematodes. The efficacy of FM to reduce infection of M. incognita in cucumber was evaluated under greenhouse and field conditions. In the greenhouse, FM at all test rates resulted in a 22.5 to 39.6% and 31.3 to 55.0% reduction in the population density of M. incognita in the soil at 30 and 60 days after treatment (DAT), respectively, compared with the nontreated control. FM at 500 and 750 g ha-1 reduced (P < 0.05) root galling, meanwhile increasing plant height compared with the nontreated control at 30 and 60 DAT. In the field trials, FM at 500 and 750 g ha-1 decreased the population density of M. incognita and root galling 57.2 to 69.9% compared with the untreated control, while enhancing cucumber yield in two consecutive years. Furthermore, FM at 500 g ha-1 combined with fosthiazate was the most effective treatment showing a synergistic effect on reducing population densities of M. incognita, which was significantly greater than either FM or fosthiazate by themselves. In summary, FM has considerable potential for managing M. incognita on cucumber.

Oxidative stress, intestinal damage, and cell apoptosis: Toxicity induced by fluopyram in Caenorhabditis elegans.

Fluopyram, a succinate dehydrogenase inhibitor fungicide and nematicide, has been used extensively for agricultural pest control and toxicologically affects non-target organisms. In the present study, Caenorhabditis elegans, a well-established model organism, was used to evaluate the toxic effect of fluopyram and the possible molecular mechanisms. C. elegans was exposed to fluopyram for 24 h at three sublethal concentrations (0.01, 0.05 and 0.25 mg/L) and the physiological, biochemical, and molecular indicators were examined. The results showed that sublethal exposure to fluopyram could cause damage to growth, locomotion behavior, feeding, lifespan and reproduction of the nematodes. Fluopyram exposure induced oxidative stress as indicated by increase of ROS production, lipofuscin and lipid accumulation, and MDA level in the nematodes. In contrast, exposure to fluopyram significantly decreased the activities of target enzyme SDH and antioxidant enzymes including SOD, CAT and GST. Moreover, the expression of genes associated with oxidative stress (e.g., gst-4, sod-3, fat-7, mev-1 and daf-16), intestinal damage (e.g., mtm-6, nhx-2, opt-2, pkc-3, par-6, act-5 and egl-8), and cell apoptosis (e.g., ced-13, ced-3, egl-38, efl-2, cep-1 and lgg-1) was significantly influenced after exposure to fluopyram. According to Pearson correlation analyses, significant correlation existed between 190 pairs of parameters, which indicated that fluopyram induced multiple toxic related effects in C. elegans. These findings suggest that oxidative stress, intestinal damage, and cell apoptosis may play major roles in toxicity of fluopyram in the nematodes.

Synergistic Effect of Combined Application of a New Fungicide Fluopimomide with a Biocontrol Agent Bacillus methylotrophicus TA-1 for Management of Gray Mold in Tomato.

Gray mold caused by Botrytis cinerea can be a severe disease of tomato infecting leaves and fruits of tomato plants. Chemical control is currently the most effective and reliable method; however, application of fungicides has many drawbacks. The combination of biological control agents with newly developed fungicides may be a practicable method to control B. cinerea. Fluopimomide is a newly developed fungicide with a novel mode of action. Bacillus methylotrophicus TA-1, isolated from rhizosphere soil of tomato, is a bacterial strain with a broad spectrum of antimicrobial activities. Little information is currently available about the effect of fluopimomide and its integrated effect on B. cinerea. Therefore, laboratory, pot, and field experiments were carried out to determine the effects of fluopimomide alone and in combination with B. methylotrophicus TA-1 against gray mold on tomato. The in vitro growth of B. methylotrophicus TA-1 was unaffected by 100 mg liter-1 fluopimomide. Inhibition of B. cinerea mycelial growth was significantly increased under combined treatment of fluopimomide and B. methylotrophicus TA-1. In greenhouse experiments, efficacy against gray mold was significantly greater by an integration of fluopimomide and B. methylotrophicus TA-1 than by either alone; control efficacy of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 at 108 colony-forming units (cfu) ml-1 reached 70.16 and 69.32%, respectively, compared with the untreated control. In both field trials during 2017 and 2018, control efficacy was significantly higher for the combination of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 than for either treatment alone. The results from this study indicated that integration of the new fungicide fluopimomide with the biocontrol agent B. methylotrophicus TA-1 synergistically increased control efficacy of the fungicide against gray mold of tomato.

Characterization of Antagonistic Bacillus methylotrophicus Isolated From Rhizosphere and Its Biocontrol Effects on Maize Stalk Rot.

Stalk rot is one of the most serious and widespread diseases in maize, and effective control measures are currently lacking. Therefore, this study aimed to develop a new biological agent to manage this disease. An antagonistic bacterial strain, TA-1, was isolated from rhizosphere soil and identified as Bacillus methylotrophicus based on morphological and biochemical characterization and 16S ribosomal RNA and gyrB gene sequence analyses. TA-1 exhibited a strong antifungal effect on the growth of Fusarium graminearum mycelium, with 86.3% inhibition at a concentration of 108 CFU per ml. Transmission electron microscopy showed that TA-1 could disrupt the cellular structure of the fungus, induce necrosis, and degrade the cell wall. Greenhouse and field trials were performed to evaluate the biocontrol efficacy of TA-1 on maize stalk rot, and the results of greenhouse experiment revealed that the bacterium significantly reduced disease incidence and disease index. Seeds treated with a 108 CFU ml-1 cell suspension had the highest disease suppression at 86.8%. Results of field trials show that seed bacterization with TA-1 could not only reduce maize stalk rot incidence but also increase maize height, stem diameter, and grain yield. The lipopeptide antibiotics were isolated from the culture supernatants of TA-1 and identified as surfactins and iturins. Consequently, B. methylotrophicus TA-1 is a potential biocontrol agent against maize stalk rot.

Effects of fumigation with 1,3-dichloropropene on soil enzyme activities and microbial communities in continuous-cropping soil.

The compound 1,3-D (1,3-dichloropropene) is a potential candidate soil fumigant due to the restrictions on methyl bromide (MB). To date, little is known about the soil microbial community changes induced by 1,3-D fumigation. Therefore, soil properties, related soil enzymes, genes encoding the key enzymes of ammonia oxidation in both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) and bacterial diversity were investigated to assess the effects of 1,3-D fumigation on the soil microbial community. The results exhibited that fumigation with 1,3-D caused accumulation of NH4+-N, but it led to decrease in the rate of NO3--N, and the concentration of NO3--N gradually recovered. At 12 weeks after transplant (WAT) of tomato seedlings, the concentration of NH4+-N and NO3--N were not statistically significant between the 1,3-D treatment groups and the untreated control group. A similar tendency was found for organic matter, soil pH, urease and protease activities. Moreover, quantitative real-time PCR (qPCR) showed that 1,3-D decreased total bacterial abundance, AOA-amoA and AOB-amoA genes. In addition, Illumina MiSeq sequencing analysis revealed that soil bacterial community diversities were significantly reduced at earlier sampling time points, and at later sampling time points, soil bacterial diversity gradually recovered, there was no significant difference compared to the control group. The present study provides useful information to evaluate the environmental safety of 1,3-D.

Single basal application of thiacloprid for the integrated management of Meloidogyne incognita and Bemisia tabaci in tomato crops.

Tomato growers commonly face heavy nematode (Meloidogyne incognita) and whitefly (B-biotype Bemisia tabaci) infestations, and previous studies demonstrated that thiacloprid could be used to control M. incognita and B. tabaci in cucumber. However, the efficacy of a single basal application of thiacloprid to control both pests and its effect on yield in tomato remains unknown. In this study, the potential of thiacloprid application to the soil for the integrated control of M. incognita and B. tabaci in tomato was evaluated in the laboratory and the field. Laboratory tests showed that thiacloprid was highly toxic to whitefly adults and eggs with an average lethal concentration 50 (LC50) of 14.7 and 62.2 mg ai L-1, respectively, and the LC50 of thiacloprid for nematode J2s and eggs averaged 36.2 and 70.4 mg ai L-1, respectively. In field trials, when thiacloprid was applied to the soil at 7.5, 15 and 30 kg ha-1 in two consecutive years, whitefly adults decreased by 37.8-75.4% within 60 days of treatment, and the root-galling index was reduced by 31.8-85.2%. Optimum tomato plant growth and maximum yields were observed in the 15 kg ha-1 treatment. The results indicated that a single basal application of thiacloprid could control M. incognita and B. tabaci and enhance tomato growth and yield.

Effect of Abamectin on the Cereal Cyst Nematode (CCN, Heterodera avenae) and Wheat Yield.

The cereal cyst nematode (CCN, Heterodera avenae) is a major pest in wheat and until now there is no pesticide registered to control this pest in China. Development of effective methods of controlling CCN is urgently needed. Abamectin is a biological pesticide that has a high nematicide activity. However, the efficacy of abamectin soil application to control CCN in wheat and its effect on yield in China remains unknown. Therefore, laboratory, greenhouse, and field tests were carried out to evaluate the potential of abamectin soil applications for CCN control and improvement of wheat yield. Laboratory tests showed that abamectin exhibited knockdown toxicity to CCN, with LC50 and LC90 values 9.8 and 59.4 mg liter-1. Greenhouse experiment and field trials showed that soil applications of abamectin provided significant CCN control and higher straw dry weights and wheat grain yields. There was an 8.5 to 19.3% yield increase from the various abamectin treatments compared with the control. The results of this study demonstrated that abamectin exhibited a high nematicidal activity to H. avenae and adequate performance to enhance wheat crop yields.

Effect of Emamectin Benzoate on Root-Knot Nematodes and Tomato Yield.

Southern root-knot nematode (Meloidogyne incognita) is an obligate, sedentary endoparasite of more than 3000 plant species, that causes heavy economic losses and limit the development of protected agriculture of China. As a biological pesticide, emamectin benzoate has effectively prevented lepidopteran pests; however, its efficacy to control M. incognita remains unknown. The purpose of the present study was to test soil application of emamectin benzoate for management of M. incognita in laboratory, greenhouse and field trials. Laboratory results showed that emamectin benzoate exhibited high toxicity to M. incognita, with LC50 and LC90 values 3.59 and 18.20 mg L(-1), respectively. In greenhouse tests, emamectin benzoate soil application offered good efficacy against M. incognita while maintaining excellent plant growth. In field trials, emamectin benzoate provided control efficacy against M. incognita and resulted in increased tomato yields. Compared with the untreated control, there was a 36.5% to 81.3% yield increase obtained from all treatments and the highest yield was received from the highest rate of emamectin benzoate. The results confirmed that emamectin benzoate has enormous potential for the control of M. incognita in tomato production in China.

Effect of abamectin on root-knot nematodes and tomato yield.

BACKGROUND: Tomato growers in Shandong Province, China, commonly face heavy root-knot nematode infestations. Current methods of control include cadusafos and methyl bromide (MeBr), but alternative methods are required because of the high toxicity of these pesticides and the ecological risk of their use. Therefore, abamectin soil applications were evaluated for their potential to control soil nematodes in a series of laboratory tests, greenhouse pot experiments and field trials. RESULTS: Laboratory tests showed that abamectin exhibited rapid knockdown of Meloidogyne incognita, with LC(50) and LC(90) values that were superior to those of cadusafos and averaged 7.06 and 21.81 mg L(-1). In the greenhouse pot experiment, soil applications of abamectin provided significant M. incognita control similar to that provided by cadusafos while maintaining excellent plant height and vigour. In the field trials, abamectin exhibited excellent control effects to nematodes while giving a higher tomato yield. There was a 19.3-39.0% yield increase from the various treatments compared with the control, and the best results were obtained from the highest dose of abamectin. CONCLUSION: The results of this study demonstrated that abamectin has the potential to be used as an effective alternative to MeBr and cadusafos for nematode control in tomato production in Shandong Province.

Managing root-knot nematodes and weeds with 1,3-dichloropropene as an alternative to methyl bromide in cucumber crops in China.

1,3-dichloropropene (1,3-D) was evaluated as a potential alternative for the widely used soil fumigant methyl bromide (MeBr) in cucumber (Cucumis sativus Linn.) crops in China. Six treatments were replicated five times in a randomized complete block design: fumigation with MeBr (400 kg·ha(-1)), three 1,3-D doses (90, 120, and 180 L·ha(-1)), an avermectin dose (7.5 L·ha(-1)), and a nontreated control. Results consistently indicated that MeBr was generally superior to the treatments involving all 1,3-D and avermectin, which in turn were superior to the control, for improving cucumber yield and to control nematode and weed. In two successive seasons, 1,3-D at a dose of 180 L·ha(-1) was as effective as MeBr in increasing plant height, vigor, and yield, as well as showed excellent nematode control efficiency, but it had relatively poor potency to control weeds. The present data support the conclusion that 1,3-D is a promising MeBr alternative for managing nematodes and weeds in cucumber crops and can be used in integrated pest management programs.

Evaluation of 1,3-dichloropropene as a methyl bromide alternative in tomato crops in China.

1,3-Dichloropropene (1,3-D, C3H4Cl2) is a potential candidate as a soil disinfectant because of the restriction of methyl bromide (MeBr) in soil fumigation due to its ecological risk. Field trials were conducted to ascertain the efficiency of 1,3-D as a MeBr alternative in tomato ( Solanum lycopersicum L.) and evaluate its application prospects in China. Five treatments were replicated five times in a randomized complete block design: fumigation with MeBr (400 kg ha(-1)), three 1,3-D doses (180, 120, and 90 L ha(-1)), an avermectin dose (7.5 L ha(-1)), and a nontreated control. Results consistently indicated that MeBr was generally superior to the treatments involving all 1,3-D levels and avermectin, which in turn were superior to the control, for improving tomato yield and inhibiting nematode, weed, and mortality caused by plant disease. In both seasons, 1,3-D at the dose of 180 L ha(-1) was as effective as MeBr in increasing plant height, vigor, and tomato yield and in reducing the incidence of soilborne disease, especially in maintaining excellent nematode control efficiency, but it provided relatively poor control over weeds. On the basis of these results, 1,3-D, in combination with other alternatives to MeBr, is recommended to achieve integrated pest management.