Understanding Occurrence Regularity and Preventive Measure for Panax notoginseng Leaf Spot Disease in Forest Environments

Panax notoginseng (Burk.) F. H. Chen, a valuable Chinese herb in Yunnan Province, is susceptible to leaf spot caused by Boeremia linicola. Nonetheless, effective control methods against leaf spot in P. notoginseng are lacking. We surveyed understorey P. notoginseng bases in Lincang, Lancang, and Xundian, with incidence rate reaching 80% and an average disease index of 25 in severe cases. We found that pathogenic bacteria overwinter in infected leaves and soil, with conidia and conidiophores serving as the primary infection source. The strain B. linicola LYB-2 showed the best growth at 20°C and pH 5.0. We also screened control agents using the plate and face-off culture methods. Tetramycin exhibited 38.56–74.67% inhibition with an EC50 of 0.60 mg/L. Copper abietate showed 3.10–34.76% inhibition with an EC50 of 3,120.05 mg/L. Trichoderma atroviride and T. harzianum exhibited inhibition rates of 52.48% and 44.19%, respectively, while Bacillus subtilis reached 78.45%. Field tests demonstrated significant control effects with 20% copper abresinate, B. subtilis, T. virenceae BH-10 preparation, and 0.3% tetramycin, achieving 82.57%, 72.56%, 71.3%, and 70.2% inhibition, respectively. These findings support their eco-friendly use for preventing and controlling leaf spot disease in P. notoginseng forests; we provide vital scientific evidence for disease prediction and green control strategies.