The phytopathogenic oomycete Phytophthora litchii is the culprit behind the devastating disease known as \"litchi downy blight\", which causes large losses in litchi production. Although fluopimomide exhibits strong inhibitory efficacy against P. litchii, the exact mechanism of resistance is still unknown. The sensitivity of 137 P. litchii isolates to fluopimomide was assessed, and it was discovered that the median effective concentration (EC50) of the fungicide had a unimodal frequency distribution with a mean value of 0.763 ± 0.922 μg/mL. Comparing the resistant mutants to the equivalent parental isolates, the resistance mutants\' survival fitness was much lower. While there was no cross-resistance between fluopimomide and other oomycete inhibitors, there is a notable positive cross-resistance between fluopimomide and fluopicolide. According to the thorough investigation, P. litchii had a moderate chance of developing fluopimomide resistance. The point mutations N771S and K847N in the VHA-a of P. litchii (PlVHA-a) were present in the fluopimomide-resistant mutants, and the two point mutations in PlVHA-a conferring fluopimomide resistance were verified by site-directed mutagenesis in the sensitive P. capsici isolate BYA5 and molecular docking.

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.

To evaluate the residue levels of fluopimomide, pyraclostrobin and its metabolite BF-500-3 in garlic ecosystems, supervised garlic field trials with a commercial formulation (pyraclostrobin·fluopimomide 30% suspension concentrate (SC)) were conducted in six regions of China according to the Good Agricultural Practices (GAP). The residues of fluopimomide, pyraclostrobin and BF-500-3 in field samples were determined using a QuEChERS method combined with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The average recoveries of all target compounds were 76-94% with relative standard deviations (RSDs) of 1.0-14.5% and limits of quantitation (LOQs) of 0.002 mg/kg. At the recommended pre-harvest interval (PHI, 10 days), the residues of fluopimomide, pyraclostrobin and BF-500-3 were below 0.16, 0.77 and 0.12 mg/kg in garlic chive; below 0.027, 0.22 and 0.002 mg/kg in garlic scape; and below 0.002, 0.002 and 0.002 mg/kg in garlic, respectively. Dietary intake risks were calculated using risk quotients (RQs) based on field residual data, toxicological data and dietary patterns. The chronic dietary risk quotients (RQc) of pyraclostrobin and fluopimomide were 48.42% and 0.36%, respectively. The acute dietary risk quotients (RQa) of pyraclostrobin in garlic were 0.06-0.15%. These results indicated a low dietary risk for consumers. This study could provide scientific guidance for the application of pyraclostrobin and fluopimomide in garlic.

Fluopimomide is a novel acid amide fungicide registered for the control of many plant pathogens. In the present study, the effects of soil-treated fluopimomide on soil micro biomass, disease incidence, plant growth, soil enzyme activity, and marketable yield of tomato (Solanum lycopersicum L.) were investigated via field trial. In addition, the application prospect in China was also evaluated. In the experiment, five treatments with three replications and a randomized complete block design were followed. The treatments were: furrow application of fluopimomide (25% suspension concentrate, SC) at the dosage of 375, 750, and 1,500 g ha-1, which was recommended, double recommended, and quadruple recommended dosages, respectively. Besides, common control fungicide fluopicolide (5% SC) furrow was applied at recommended application dosages of 750 mL ha-1, and a non-treated control was also undertaken. Results indicated that fluopimomide exhibited no effects on the amount of soil bacteria and actinomycetes, and its inhibition effect on fungi amount could be recovered at 60 days after treatment (DAT). With the recommended application dosage, fluopimomide could efficiently reduce the number of plant pathogens in soil by 79.56-85.80%, significantly reduce the disease incidences in tomato plants by 80.00-88.24%, and improve plant height by 13.25-24.05% and marketable yield by 16.88%. Furthermore, soil enzymes exhibited a complex response to fluopimomide, and AOB and nifH gene copy numbers were increased by the double and quadruple recommended dosage of fluopimomide. Based on the above results, fluopimomide could be recommended as an efficient fungicide for the tomato field.

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.

Cucumber 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, a new chemical having a similar structure to fluopyram, was shown to exhibit toxic effects on fungi and nematodes. The efficacy of fluopimomide to reduce infection of M. incognita in cucumber was evaluated under greenhouse and field conditions. In the greenhouse, fluopimomide at all test rates resulted in a 22.5-39.6% and 31.3%-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 non-treated control. Fluopimomide at 500 and 750 g ha-1 reduced (p < 0.05) root galling, meanwhile increasing plant height compared to the non-treated control at 30 and 60 DAT. In the field trials, fluopimomide at 500 and 750 g ha-1 decreased the population density of M. incognita and root galling 57.2-69.9% compared to the untreated control, while enhancing cucumber yield in two consecutive years. Furthermore, fluopimomide 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 fluopimomide or fosthiazate by themselves. In summary, fluopimomide has considerable potential for managing M. incognita on cucumber.

Dimethomorph is a morpholine broad-spectrum fungicide and effectively controls taro blight, cucumber downy mildew, rice blast disease, and others. Fluopimomide is a newly developed broad-spectrum fungicide to primarily control oomycetes and rhizoctonia diseases. Taro, one of the earliest cultivated crops, is a staple food in Africa, Oceania, and Asia. Recently, a commercial suspension concentrate formulation containing 15% fluopimomide and 25% dimethomorph has been registered in China, the second largest taro producer in the world. The objective of this study was to develop a high-performance liquid chromatography tandem mass spectrometry method to detect the residues of fluopimomide and dimethomorph concurrently in taro samples. The results showed that the average recoveries of fluopimomide and dimethomorph ranged from 83 to 108%, and relative standard deviations (RSD) ranged from 1 to 11%. The limit of quantitation (LOQ) was 0.01 mg kg-1 for the two compounds. The dissipation results demonstrated that both fluopimomide and dimethomorph in taro degraded rapidly in taro fields, and the residues of the two fungicides were below the LOQ within 14 days post-application. The final residue levels of fluopimomide and dimethomorph in taro were lower than 0.066 mg kg-1 28 days post-application. For dietary risk assessments, the dietary structure of different genders and age of people in China exposure risk assessment and whole diet exposure risk assessment shows that the risk quotient (RQ) values were substantially lower than 100%, suggesting that the long-term risks of fluopimomide/dimethomorph mixed formulation in taro at the recommended dosage were negligible. In summary, our combined results from the dissipation behaviors, terminal residues, and dietary risk assessments provide the critical empirical data for the establishment of the maximum residue levels (MRLs) of the two broad-spectrum fungicides in taro, a traditional food for African, Oceanic, and South Asian cultures.

Potato late blight is a severe and highly epidemic disease caused by Phytophthora infestans that can affect all parts of the plant. This study mainly screened antagonistic strains for good control of potato late blight and identified strain SDTB038 as Bacillus velezensis according to its morphological and chemical properties and the 16S rRNA, gyrA, and gyrB gene sequences. This antagonistic strain achieved good control of potato late blight in greenhouses and fields and promoted potato plant growth. Two-year field trials (2018 and 2019) showed that B. velezensis SDTB038 can be used to reduce food losses caused by late blight, achieving late blight reductions of 40.79% (2018) and 37.67% (2019). In two-year field trials, the control effects of the highest concentrations of fluopimomide and B. velezensis SDTB038 were better than those of the other treatments. The control effect of 85 g ha-1 fluopimomide and B. velezensis SDTB038 and that of 170 g ha-1 fluopimomide alone showed no significant differences. These field results indicate that a low concentration of fungicide and a high concentration of SDTB038 can be effective in controlling potato late blight. Foliar detection showed that lipopeptides have an inhibitory effect on P. infestans. The amplification of lipopeptide genes revealed surfactin (srfAB and srfAC) and fengycin (fenB) genes in SDTB038, but only surfactin production by B. velezensis SDTB038 was observed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry analysis. Therefore, the strain B. velezensis SDTB038 can produce secondary metabolites that help potato plants resist late blight development, can effectively inhibit the infection of potato leaves by P. infestans, and has potential value for development as a biological pesticide against potato late blight.