Abstract:

To explore the field control efficacy of different dosages of antibacterial lipopeptides against black shank disease of flue-cured tobacco cultivar ‘Yunyan 100’ (the dominant flue-cured tobacco variety cultivated in Huize County, Yunnan Province), as well as its effects on tobacco leaf yield and quality, a field trial was conducted in a plot severely affected by tobacco black shank disease in Malu Village, Malu Township, Huize County in 2024. Three dosage gradients of antibacterial lipopeptides (0.75 kg/hm², 1.5 kg/hm², 2.25 kg/hm²) were set for the experiment. The commonly used 40% dimethomorph was set as the positive control, and clear water served as the blank control. The disease index and control efficacy of tobacco black shank disease were surveyed at 15, 30, 45 and 60 days after tobacco transplanting, respectively. The main agronomic traits of tobacco plants under each treatment were determined at the vigorous growth stage. After harvesting and curing, the yield and grade quality of tobacco leaves were statistically analyzed, and the conventional chemical components of middle tobacco leaves (C3F) were determined simultaneously. The results showed that: (1) all treatments could effectively control tobacco black shank disease, and the overall control efficacy was ranked as follows: antibacterial lipopeptides 2.25 kg/hm² > 1.5 kg/hm² > 0.75 kg/hm² > 40% dimethomorph (300 mL/hm²). At 60 days after tobacco transplanting, the control efficacies of the three dosages of antibacterial lipopeptides ranged from 70.39% to 83.21%, which were significantly higher than the 62.63% achieved by dimethomorph. (2) For the antibacterial lipopeptides treatment at 2.25 kg/hm², no significant differences were observed in maximum leaf length and leaf width compared with the 1.5 kg/hm² treatment; other agronomic trait indicators were significantly superior to the 1.5 kg/hm² antibacterial lipopeptides treatment. Furthermore, the main agronomic traits under the three dosages of antibacterial lipopeptides were significantly better than those of the positive control. (3) The treatment of 1.5 kg/hm² presented the best performance regarding tobacco leaf chemical components, yield and quality, with more harmonious chemical components. Therefore, under the ecological conditions in Huize County, the optimal application dosage of antibacterial lipopeptides for the control of black shank disease in ‘Yunyan 100’ is 1.5 kg/hm². Its control efficacy is superior to the traditional chemical pesticide dimethomorph. Meanwhile, it possesses multiple functions including disease prevention, growth promotion, quality improvement and optimization of internal chemical components of tobacco leaves, hence being suitable for popularization and application in the green production of local flue-cured tobacco.

Key words: antibacterial lipopeptide, dimethomorph, ‘Yunyan 100’, tobacco black shank, application rate