Background: Sclerotium rolfsii, the causal agent of peanut southern blight, has become increasingly prevalent and harmful in China, causing serious economic losses to the peanut industry. To effectively manage peanut southern blight, this study evaluated the bioactivity of the new-generation sterol demethylation inhibitor (DMI) fungicide mefentrifluconazole against peanut S. rolfsii.Results: In this study, the DMI fungicide mefentrifluconazole exhibited excellent inhibitory activity against the mycelial growth of S. rolfsii, with a mean EC 50 value of 0.21 ± 0.11 mg L −1 and a range of 0.02 to 0.55 mg L −1 for 261 isolates collected from Hebei, Henan and Shandong provinces. Mefentrifluconazole significantly reduced the biomass of mycelia and affected the morphology of hyphae. Although sclerotia were more tolerant to mefentrifluconazole than mycelial growth, mefentrifluconazole greatly inhibited the formation and germination of sclerotia. In addition, sclerotia produced by mefentrifluconazole-treated mycelia were deficient in nutrients (e.g., protein, carbohydrate and lipid). These results indicated that mefentrifluconazole may reduce the population of S. rolfsii in the following year. In greenhouse experiments, mefentrifluconazole showed control efficacy and good persistence against peanut S. rolfsii. The preventative and curative activities of mefentrifluconazole at 200 mg L −1 against southern blight still reached 95.36% and 60.94%, respectively, after 9 days of application. No correlation was observed for the sensitivity of S. rolfsii to mefentrifluconazole and the tested DMI, quinone outside inhibitor and succinate dehydrogenase inhibitor fungicides. Conclusion: All data indicated that mefentrifluconazole could provide favorable control efficacy against S. rolfsii from peanuts and reduce the infection and population of S. rolfsii in the following year.

BackgroundBenzothiazole is a potential grain fumigant for Tribolium castaneum. However, its safety profile and suitable fumigation conditions remain unknown. We therefore investigated the insecticidal efficacy, accumulation and dissipation of benzothiazole in grains (wheat, corn and rice) under different temperatures.ResultsWe established a universal detection method (modified QuEChERS coupled with GC–MS/MS) of benzothiazole residues in three grains, which provided high linearity (R2 > 0.999), sensitivity (limits of detection = 0.001 mg/kg, limits of quantification = 0.002–0.005 mg/kg), accuracy (recoveries = 88.18–118.75%) and precision (relative standard deviations < 4.78%). The insecticidal efficacy order of benzothiazole was 30 ≥ 10 > 20 °C and corn > wheat > rice. Temperature positively affected the accumulation/dissipation rate of benzothiazole. Rice was the most easily accumulated and dissipated grain for benzothiazole residues, while corn accumulated benzothiazole more than wheat but less than rice, with dissipation slower than wheat and rice.ConclusionOur results provide important references for the application of benzothiazole and other fumigants. © 2023 Society of Chemical Industry.

Athelia rolfsii is a devastating soil-borne pathogen that causes stem rot of peanut and severely constrains the peanut production. The new generation of succinate dehydrogenase inhibitor (SDHI) fungicide benzovindiflupyr has been registered in United States and Brazil for managing multiple plant diseases. However, it is not registered in China to control peanut stem rot. In this study, 246 isolates obtained from major peanut production areas in Shandong, Henan and Hebei Province of China were used to determine the baseline sensitivity of A. rolfsii to benzovindiflupyr. The frequency of EC50 values of benzovindiflupyr was unimodally distributed with an average EC50 of 0.12 mg/L and a range of 0.01-0.57 mg/L. Benzovindiflupyr can also strongly inhibit the germination of sclerotia, with an average EC50 of 2.38 mg/L (N= 23). In addition, benzovindiflupyr exhibited great in vivo efficacy against A. rolfsii, that the protective or curative efficacy (89.87%, 20.39%) of benzovindiflupyr at a concentration of 50 mg/L was equivalent to that of the control fungicide thifluzamide at 100 mg/L (86.39%, 16.21%). At the same concentration (e.g., 100 mg/L), the protective efficacy (93.99%) of benzovindiflupyr was more than twice as high as the curative efficacy (45.07%). A positive correlation was existed between benzovindiflupyr and isopyrazam or mefentrifluconazole, which was possibly resulted from similar chemical structures or the damage of cell membrane. Our findings provided valuable information for the application of benzovindiflupyr, and the established baseline sensitivity could facilitate the monitoring and assessment of benzovindiflupyr resistance risk.