Improved Management of Verticillium Wilt in Smoke Trees Through the Use of a Combination of Fungicide and Bioagent Treatments

Smoke tree (Cotinus coggygria) is an important component of the urban landscape and represents red-leaf scenery in Beijing; however, Verticillium wilt, caused by Verticillium dahliae, has caused high mortality of smoke trees. Traditional control methods, such as chemical root irrigation and trunk injection, are problematic due to environmental pollution and potential plant damage. This study aimed to explore effective prevention and control methods for Verticillium wilt of smoke tree across different regions of red-leaf scenery in Beijing. In 2023, 240 smoke trees from the Pofengling Park of Beijing were selected for the study. Four different fungicides, a plant growth regulator and a biocontrol agent were tested. Three application methods (root irrigation, trunk spraying, and a combination of both) were used in the different trials. Based on the results of the 2023 trial, control trials were conducted under the disease classification in 2024 at key red-leaf scenery regions, such as Xiangshan Park, Xishan Park, and Pofengling Park. The bioagents of Bacillus subtilis root irrigation combined with the trunk spraying treatment group showed the best disease control effects. Calculated by the change in disease index in the treatment and blank groups, the corrective control effect in the treatment group reached 104.55%, and 60% of the plants remained healthy, indicating that this method of disease control was the most effective. Propiconazole root irrigation also had a significant effect on diseased smoke trees. Furthermore, validation experiments conducted in 2024 confirmed that various combinations of root irrigation and trunk spraying provided strong preventive and therapeutic effects on Verticillium wilt. In conclusion, the graded control measures demonstrated effective control of wilt at different disease index grades. This study offers an effective and practical solution for controlling Verticillium wilt, benefiting both environmental sustainability and landscape health.