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BACKGROUND: Double‐cropping is a common practice in vegetable plasticulture whereby a second crop is planted on the same plastic bed as the first crop. Root‐knot nematodes (Meloidogyne spp.) are one of the major soilborne constraints in double‐cropped vegetables due to nematode population build‐up on the first crop. We evaluated the effect of fumigant and non‐fumigant nematicides applied on the first crop, on nematode infection and yield of the second crop in 10 field trials between 2017 and 2020. Fumigants were chloropicrin (Pic100), chloropicrin +1,3‐D (PicClor60), and non‐fumigant nematicides were oxamyl (Vydate), fluensulfone (Nimitz), fluopyram (Velum) and fluazaindolizine (Salibro). The first crop was tomato and double crops were cucumber, squash, zucchini, and cantaloupe. RESULTS: Fumigation with chloropicrin on the first crop increased root‐knot nematode damage on the double‐crop at the end of the season in seven trials, while the opposite was noted in one trial, and no difference was noted in two trials. Fumigation with chloropicrin+1,3‐D resulted in root‐knot nematode damage less than chloropicrin but more than non‐fumigated plots. Cucurbit yield was greater in non‐fumigated beds in four trials, and in chloropicrin‐treated beds in two trials. Fluensulfone reduced root‐knot nematode damage on the second crop in five out of 10 trials. CONCLUSION: Our results indicate that chloropicrin applied on the tomato crop may lead to increased root‐knot nematode damage on the double crop. More research is needed to understand the processes behind this, but it is possibly related to a reduction in natural nematode soil suppressiveness due to the broad‐spectrum fungicidal activity of chloropicrin. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND Fluazaindolizine is a novel sulfonamide nematicide that is currently under commercialization in various countries. Four trials (two in tomato, two in zucchini) were carried out over two growing seasons in a root‐knot nematode (RKN; Meloidogyne incognita)‐infested plastic house to test the effects of a single application of fluazaindolizine at 1000 and 2000 g ha–1, on RKN, the resident nematode community and to estimate any side effects on the soil food web and soil ecological functions. The composition of the nematode community was evaluated at three sampling times, pre‐treatment (before soil preparation), at planting (after nematicide application) and at harvest. Nematode abundance and nematode‐based ecological indices, such as maturity indices, soil food web indices (Structure, Basal, Enrichment index) and metabolic footprints were calculated and compared between the untreated and nematicide treatments at various sampling times. RESULTS: In both crops the test rates of fluazaindolizine significantly reduced both the soil numbers of RKN as well as the observed root galling at harvest. Fluazaindolizine treatments showed a low impact on the numbers of other plant‐parasitic nematodes, and at harvest the numbers of some ectoparasites as Telotylenchus even showed higher values within the nematicide‐treated plots than in the untreated control. Overall, fluazaindolizine treatments neither decreased the bacterivorous, fungivorous or omnivorous nematode densities, nor reduced the maturity and soil food web indices. However, we observed some slight reductions in the structure index as well as increases in the basal index that might indicate some adverse impact on soil functions resulting from the nematicide application. Still those impacts were considered small compared to the impact of the soil preparation. CONCLUSIONS: Overall, fluazaindolizine showed a good level of selectivity towards RKN and therefore could become a useful tool within integrated nematode management approaches that also complements soil health and maintaining diversity in soil. [ABSTRACT FROM AUTHOR]

Background: Root‐knot nematodes are plant‐parasitic nematodes that cause immense damage to a broad range of cultivated crops by forming root galls, resulting in yield losses in crops. To facilitate the development of faster‐acting selective nematicides, we cloned three cDNAs encoding UNC‐49B proteins from the southern root‐knot nematode Meloidogyne incognita and examined their functional and pharmacological properties by two‐electrode voltage clamp electrophysiology using a Xenopus oocyte expression system. Results: The three cloned cDNAs encoded Min‐UNC‐49B, Min‐UNC‐49B‐L and Min‐UNC‐49B‐XL; the last two proteins have longer N‑terminal regions than the first protein. When expressed in Xenopus oocytes, these proteins responded to γ‐aminobutyric acid (GABA) to activate currents with high‐micromolar or low‐millimolar half‐maximal effective concentration (EC50) values, indicating the formation of functional homo‐pentameric GABA receptors. Fipronil and picrotoxinin inhibited GABA‐induced currents with high‐nanomolar and low‐micromolar half‐maximal inhibitory concentration (IC50) values, respectively, in oocytes expressing Min‐UNC‐49B. The G2′A and T6′M mutations in the second transmembrane domain of Min‐UNC‐49B enhanced and reduced the sensitivity of Min‐UNC‐49B to these two antagonists, respectively. Samaderine B and SF‐14 inhibited GABA responses in oocytes expressing Min‐UNC‐49B with low‐micromolar and high‐nanomolar IC50 values, respectively. Ivermectin, α‐terpineol, thymol and methyl eugenol exerted dual effects on Min‐UNC‐49B by potentiating currents induced by low concentrations of GABA and inhibiting currents induced by high concentrations of GABA. Conclusion: We have shown that structurally diverse compounds act at Min‐UNC‐49B GABA receptors. Our results may serve as a starting point to decipher the molecular function of native GABA receptors of plant‐parasitic nematodes, which could aid in the structure‐based design of novel nematicides. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND: Emamectin benzoate (EB) has recently been successfully applied as a trunk injection for preventative control of the pine wilt disease (PWD) caused by Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle. Here, a whole‐organism transcriptomic analysis provides comprehensive insights into the adverse effects of EB on B. xylophilus. RESULTS: A large set of differentially expressed genes (DEGs) were found, demonstrating the antagonistic effects of EB on B. xylophilus embryonic and larval development, reproduction, nervous and motor systems, and pathogenesis. In toxicity assays with EB, the number of eggs laid, hatching rate, thrashing frequency, and developmental rate of B. xylophilus were significantly suppressed at low concentrations (0.1 μg mL−1). Moreover, the transcriptional changes validated by real‐time quantitative PCR showed downregulated transcript levels of the genes encoding pectate lyases, β‐1,4‐endoglucanases, and upregulated the genes encoding glutamate‐gated chloride channel, γ‐aminobutyric acid type β receptor, uridine 5′‐diphospho‐glucuronosyl transferase, ATP‐binding cassette transporter. The potential responses of B. xylophilus to EB included the upregulation of several genes putatively contributing to oocyte protection, stem cell renewal, and xenobiotic degradation, implying the potential for drug resistance to develop. CONCLUSION: Our findings further our understanding of the effects of EB for managing the PWD and may help to improve the pesticide‐use strategies for controlling B. xylophilus. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND: The application of biochar to soil is supposed to alter its adsorption/desorption potential toward pesticides, thereby affecting their bioavailability and efficacy. This is particularly relevant in the case of nematicides because these pesticides are directly applied to soil. RESULTS: Biochar was produced from date palm (PB) and eucalyptus (EB) waste at 450 °C and added at a rate of 1% to a sandy soil. The half‐life (t½) of fenamiphos was increased from 2.7 to 18.3 and 18.6 days in PB‐ and EB‐amended soils, respectively. By contrast, the half‐life of cadusafos was unaffected. Freundlich Kf values increased from 1.22 and 0.39 (μg1–Nf g−1 mLNf) to 4.49 and 6.84 in 1% PB‐amended soil, and to 3.49 and 4.62 in 1% EB‐amended soil for cadusafos and fenamiphos, respectively. Plant uptake of both nematicides in tomato seedlings was reduced by approximately 97% (cadusafos) and 85% (fenamiphos). Although nematicide efficacy against Meloidogyne incognita was not altered at the recommended dosage, it was negatively affected at a half‐dose rate. Under these conditions, it decreased from 43.1% in unamended sandy soil to only 18.3% in 1% PB‐amended soil. CONCLUSIONS: Biochar addition increased the sorption capacity of soil. This resulted in a decrease of nematicide bioavailability, together with a reduction of both the dissipation rate and uptake by tomato plants. © 2018 Society of Chemical Industry Biochar addition to soil alters nematicides sorption isotherms, thus affecting their bioavailability and dissipation rate. On the other hand, consumer risk was reduced by the decrease in plant uptake. [ABSTRACT FROM AUTHOR]

BACKGROUND Fluensulfone is a fluoroalkenyl chemical with activity against multiple genera of plant-parasitic nematodes. The adsorption, desorption, and mobility of fluensulfone were evaluated on multiple soils from the USA in laboratory and column experiments. RESULTS Adsorption data regressed to the logarithmic Freundlich equation resulted in isotherm values of 1.24 to 3.28. Soil adsorption of fluensulfone correlated positively with organic matter (0.67) and clay (0.34), but negatively with sand (-0.54). Fluensulfone soil desorption correlated to pH (0.38) and cation exchange capacity (0.44). Fluensulfone desorption from Arredondo sand soil was 26%, and from other soils ranged from 43 to 70%. In mobility experiments, fluensulfone in the leachate peaked at 3 h, gradually declining and becoming undetectable after 9 h. Recovery from leachate was 45% of the initial fluensulfone applied to the soil surface. In separate experiments, 30-cm-long soil columns were saturated with 1 L of water, and then segregated into three 10-cm sections. Fluensulfone recovery was 41, 34, 29, and 13% in Chualar sandy loam, Arredondo sand, Greenville sandy clay loam, and Tifton loamy sand, respectively, in the top 10-cm section. CONCLUSION Data indicated that soil organic matter and clay contents will affect sorption, mobility, and dissipation of fluensulfone. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Macrocyclic lactones are arguably the most successful chemical class with efficacy against parasitic nematodes. Here we investigated the effect of the macrocyclic lactone ivermectin on lipid homeostasis in the plant parasitic nematode Globodera pallida and provide new insight into its mode of action. RESULTS A non-invasive, non-destructive, label-free and chemically selective technique called Coherent anti-Stokes Raman scattering (CARS) spectroscopy was used to study lipid stores in G. pallida. We optimised the protocol using the free-living nematode Caenorhabditis elegans and then used CARS to quantify lipid stores in the pre-parasitic, non-feeding J2 stage of G. pallida. This revealed a concentration of lipid stores in the posterior region of J2 s within 24 h of hatching which decreased to undetectable levels over the course of 28 days. We tested the effect of ivermectin on J2 viability and lipid stores. Within 24 h, ivermectin paralysed J2 s. Counterintuitively, over the same time-course ivermectin increased the rate of depletion of J2 lipid, suggesting that in ivermectin-treated J2 s there is a disconnection between the energy requirements for motility and metabolic rate. This decrease in lipid stores would be predicted to negatively impact on J2 infective potential. CONCLUSION These data suggest that the benefit of macrocyclic lactones as seed treatments may be underpinned by a multilevel effect involving both neuromuscular inhibition and acceleration of lipid metabolism. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND Three field experiments evaluated the performance of the nematicide fluensulfone against the potato cyst nematode Globodera pallida in Shropshire, England. RESULTS Experiments 1 and 2 showed reduced root infection and lowered multiplication of G. pallida following fluensulfone (Nimitz 15G®) soil treatments at five rates (1.95, 3.00, 4.05 (full rate), 5.05 and 6.00 kg AI ha−1) and Nimitz 480EC® at the full rate. Experiment 3 demonstrated a positive interaction between the full rate of Nimitz 15G and the potato variety Santé in the reduction of G. pallida. The fluensulfone treatments at the full rate had more consistent effects than the lower rates, and there were no greater effects for the treatments higher than this full rate. Generally, fluensulfone was less efficacious than oxamyl or fosthiazate, which suggests that the treatment may not be reliably integrated within shorter potato rotations. CONCLUSION The data suggest that fluensulfone soil application could make a useful addition to the few available nematicide treatments for the control of G. pallida rather than be a substitute for these treatments.© 2016 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND:With theultimategoalof identifying newcompoundsactive against root-knotnematodes, a set of 14 substituted chalcones were synthesised, starting from acetophenones. These chalcones and various acetophenones were tested in vitro against Meloidogyne incognita. RESULTS: The most potent acetophenones were 4-nitroacetophenone and 4-iodoacetophenone, with EC50/24 h values of 12 ± 5 and 15 ± 4 mg L-1 respectively, somewhat weaker than that of the chemical control fosthiazate in our previous experiments (EC50/24 h 0.4 ± 0.3 mg L-1). When we converted the acetophenones to chalcones, the nematicidal activity differed, based on their substitution pattern. The condensation of 4-nitroacetophenone with 2, 4, 6-trihydroxybenzaldehyde to give the corresponding chalcone (E)-1-(4-nitrophenyl)-3-(2, 4, 6-trihydroxyphenyl)prop-2-en-1-one led to a slight reduction in activity (EC50/24 h value 25 ± 17 mg L-1). Moreover, (E)-3-(2-hydroxy-5-iodophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one showed better activity (EC50/24 h value 26 ± 15 mg L-1) than 4-methoxyacetophenone (EC50/24 h value 43 ± 10 mg L-1). CONCLUSIONS: Acetophenones and chalcones may represent good leads in the discovery of new nematicidal compounds and may have potential use in cropmanagement as active ingredients. [ABSTRACT FROM AUTHOR]

BACKGROUND: Restrictions on soil fumigants are prompting the development of new compounds for controlling nematodes, other soilborne pathogens and weeds. We evaluated the nematicidal activity of five bromine compounds against Meloidogyne javanica in vitro, and tested the two most effective ones against Pratylenchus penetrans and Xiphinema index in vitro and in soil. RESULTS: Only allyl bromide and dibromo(nitro)methane showed nematicidal activity against M. javanica juveniles in vitro at <320 mgL-1. Allyl bromide killed M. javanica and P. penetrans at 20mg L-1, and X. index at 10mg L-1, whereas 320 mg dibromo(nitro)methane L-1 was required to kill P. penetrans. Allyl bromide also showed higher nematicidal activity than dibromo(nitro)methane against M. javanica and P. penetrans in soil. Allyl bromide at 40 and 20 mg L-1 soil eliminated root galls and nematode eggs on tomato roots grown in M. javanica-inoculated loess and sandy soils respectively, showing higher nematicidal activity than 1,3-dichloropropene. No P. penetrans were recovered from soil treated with 80 mg allyl bromide L-1 soil or 320 mg dibromo(nitro)methane L-1 soil. CONCLUSION: Allyl bromide showed high nematicidal activity against all three nematode species, and nematicidal activity of dibromo(nitro)methane was discovered. These compounds could serve as new fumigation nematicides, pending further experiments. [ABSTRACT FROM AUTHOR]

BACKGROUND The fluoroalkenyl fluensulfone, known to have strong nematicidal activity against Meloidogyne spp. (root-knot nematodes), was evaluated in vitro and in soil against the migratory nematodes Bursaphelenchus xylophilus, Aphelenchoides besseyi, Aphelenchoides fragariae, Ditylenchus dipsaci, Pratylenchus penetrans, Pratylenchus thornei and Xiphinema index. RESULTS B. xylophilus and D. dipsaci were not immobilised by 48 h in vitro exposure to up to 16 mg L−1 of fluensulfone. A. besseyi and A. fragariae were affected by 8 mg L−1, the highest concentration used for these nematodes. More than 60% of P. penetrans and P. thornei were immobilised by 4 mg L−1 of fluensulfone; however, exposure of P. penetrans to the compound prior to inoculation did not affect their root penetration ability. The immobilisation rate of X. index was increased by 48 h exposure to even 1.0 mg L−1 of fluensulfone. Incorporation of over 2 mg L−1 of fluensulfone into the soil reduced populations of P. penetrans and P. thornei before and after planting lettuce and chickpea respectively. The efficacy of fluensulfone against the tested nematodes was the same or higher than that of fenamiphos in most cases. CONCLUSION A. besseyi, A. fragariae, B. xylophilus and D. dipsaci were tolerant to fluensulfone and fenamiphos. P. penetrans, P. thornei and X. index were affected by fluensulfone, but nematicidal activity was much lower than that reported for root-knot nematodes. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background Species of Cephalotaxus (the plum yews) produce nematotoxic compounds of unknown identity. Consequently, bioassay-guided fractionation was employed to identify the compound(s) in Cephalotaxus fortunei twigs and leaves with activity against plant-parasitic nematodes. Results A crude alkaloid extract, particularly drupacine, was responsible for much of the nematotoxicity. The ED50 of drupacine for Bursaphelenchus xylophilus was 27.1 µg mL−1, and for Meloidogyne incognita it was 76.3 µg mL−1. Immersion of M. incognita eggs in 1.0 mg mL−1 crude alkaloid extract (the highest tested concentration) reduced hatch by 36%; immersion of second-stage juveniles ( J2) resulted in 72-98% immobility. Crude alkaloid extract and drupacine suppressed protease activity in extracts of the microbivorous nematode Panagrellus redivivus by 50% and 80%, respectively. Application of 0.02-0.5 mg mL−1 crude alkaloid extract to soil with M. incognita inoculum did not significantly reduce pepper plant shoot length or weight, compared with nematode-inoculated, water-treated controls, but the number of eggs and J2 per root system respectively decreased by 69% and 73% at 0.5 mg mL−1. Conclusion Drupacine and a crude alkaloid extract suppress nematode hatch, activity of mixed life stages, and population numbers on plant roots. This is the first demonstration of nematotoxicity of crude Cephalotaxus alkaloids and drupacine. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article presents a study which examines the efficacy of the nematicidal activity of MCW-2, a new nematicide belonging to the fluoroalkenyl group, against Meloidogyne javanica, a root-knot nematode. It compares the efficacy of MCW2 to fenamiphos or cadusafos nematicide in tomato plants during a pot experiment. Results demonstrate the great potential of MCW-2 as a nematicide due to its nematicidal efficacy similar or even greater than that of fenamiphos or cadusafos.

The article discusses a study on clove oil from Sygygium aromaticum and its response to root-knot nematode Meloidogyne incognita. After preparation in a soy lecithin or detergent formulation, clove oil was examined to determine concentrations active against Meloidogyne incognita. The results showed that 0.097% clove oil concentration can reduce egg hatch by 50% and the viability of hatched second-stage juvenile was 0.145%. Clove oil that reduced egg hatch in water by 30% was 5.0 clove oil with decreased viability of hatched second-stage juvenile by as much as 100%.

Several concentrations of DL-methionine were tested in the laboratory for their effects on Meloidogyne incognita (Kofoid & White) Chitwood egg hatching and juvenile activity in aqueous suspensions and infested soft. After 7 days in methionine solutions, the proportions of hatched eggs were reduced by 23.3% at 0.25 mg litre-1 methionine and by 76.4% at 25 g litre-1 when compared with controls in tap water. An effect of methionine solutions on juvenile activity was also apparent after 24 h in the 25 g litre-1 treatment, where the percentage of active M incognita juveniles was reduced by 16.3%. Further reductions in nematode mobility were observed as the time of exposure increased, and at lower methionine concentrations over longer exposure times. When methionine solutions were applied to soil infested with M incognita, reductions in egg hatching and juvenile activity were observed at 0.1 and 1 mg methionine g-1 soil in both sand and clay-loam soils. The percentage of hatched eggs one week after methionine application at rates of 1 mg g-1 was lower in sand (5.6%) and clay-loam soil (20.8%) than in controls where egg hatch was 52.0% and 48.0% in sand and soil, respectively. Non-active juveniles were found at 1 mg methionine g-1 soil one week after its application to soil. [ABSTRACT FROM AUTHOR]

Background: The application of biochar to soil is supposed to alter its adsorption/desorption potential toward pesticides, thereby affecting their bioavailability and efficacy. This is particularly relevant in the case of nematicides because these pesticides are directly applied to soil., Results: Biochar was produced from date palm (PB) and eucalyptus (EB) waste at 450 °C and added at a rate of 1% to a sandy soil. The half-life (t ½ ) of fenamiphos was increased from 2.7 to 18.3 and 18.6 days in PB- and EB-amended soils, respectively. By contrast, the half-life of cadusafos was unaffected. Freundlich K f values increased from 1.22 and 0.39 (μg 1-Nf g -1 mL Nf ) to 4.49 and 6.84 in 1% PB-amended soil, and to 3.49 and 4.62 in 1% EB-amended soil for cadusafos and fenamiphos, respectively. Plant uptake of both nematicides in tomato seedlings was reduced by approximately 97% (cadusafos) and 85% (fenamiphos). Although nematicide efficacy against Meloidogyne incognita was not altered at the recommended dosage, it was negatively affected at a half-dose rate. Under these conditions, it decreased from 43.1% in unamended sandy soil to only 18.3% in 1% PB-amended soil., Conclusions: Biochar addition increased the sorption capacity of soil. This resulted in a decrease of nematicide bioavailability, together with a reduction of both the dissipation rate and uptake by tomato plants. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

Atmospheric emission of the soil fumigant 1,3-dichloropropene (1,3-D) is of environmental concern because of its toxicity and carcinogenicity. Thiosulfate fertilizers have been found to rapidly transform 1,3-D in soil to non-volatile ions which are less toxic. We investigated the use of surface application of ammonium thiosulfate (ATS) for reducing 1,3-D volatilization. In packed soil columns, emission of 1,3-D applied by sub-surface injection decreased with increasing ATS application rate and the amount of water used for delivering ATS. When ATS was applied in 9 mm water at 64 g m-2, total 1,3-D emission was reduced by 61%. The reduction was 89% when ATS was applied at193 g m-2. Bioassays showed that ATS application did not affect the effectiveness of 1,3-D for controlling citrus nematodes. In field plots where a 1,3-D emulsified formulation was applied via sub-surface drip, surface spray of ATS reduced 1,3-D emissions by 50%, and by 71% when the surface was also covered with polyethylene film. ATS application had no effect on the efficacy of root-knot nematode control or tomato yields. These results suggest that surface application of thiosulfate fertilizers may be a feasible and effective strategy for minimizing 1,3-D emissions. [ABSTRACT FROM AUTHOR]