Synergistic Control of Tobacco Fusarium Root Rot by Trichoderma asperellum and 30% Propamocarb·Azoxystrobin

The screening of the high-efficient and safe mixtures is of great importance for the prevention and control of tobacco Fusarium root rot. In this study, the mycelial growth rate method was used to determine the toxicity and compatibility and the toxicity coefficient of biocontrol agent Trichoderma asperellum Tr-0111 and chemical fungicide 30% propamocarb·azoxystrobin against F. oxysporum. In addition, their control effect on tobacco Fusarium root rot was evaluated through pot experiments. The results indicated that both 30% propamocarb·azoxystrobin and Trichoderma asperellum Tr-0111 had strong virulence against F. oxysporum, with EC₅₀ values of 0.0643 mL/L and 2.36×10² cfu/mL, and showed good compatibility. The combination of 30% propamocarb·azoxystrobin and Trichoderma asperellum Tr-0111 with different ratio showed synergistic effect, except for V_{30% propamocarb·azoxystrobin}∶V _Tr-0111=4∶6. The highest synergistic effect was obtained when 30% propamocarb·azoxystrobin and Trichoderma asperellum Tr-0111 was mixed at the ratio of 7∶3, with the synergistic ratio 1.16 and antibacterial rate 68.37%. The pot experiment showed that, the best control effect (78.18%) against tobacco Fusarium root rot was obtained when V_{30% propamocarb·azoxystrobin}∶V _Tr-0111=5∶5, followed by 7∶3 and 1∶9, with control effects of 77.27% and 72.73%, respectively. These control effects were all significantly higher than the single use of 30% propamocarb·azoxystrobin and Trichoderma asperellum Tr-0111. Therefore, to reduce the use of chemical pesticides, the mixture of 0.0643 mL/L of 30% propamocarb·azoxystrobin and 2.36×10² cfu/mL Trichoderma asperellum Tr-0111 at the ratio of 5∶5 is recommended for the control of tobacco Fusarium root rot.