Four-season Osmanthus Leaf Blight and Its Control
The health of the leaves of four-season osmanthus, as an aromatic garden plant, directly affects its ornamental value and economic returns. Leaf blight, as a typical fungal disease, has strong concealment and fast transmission. This article will systematically analyze the development pattern of the disease and provide professional control solutions.
Evolution Process of Four-season Osmanthus Leaf Blight
Incubation Period Characteristics (5-15 days)
Initial lesions appear as a yellow-green halo with a diameter of about 1mm, often starting from the leaf tip with strong transpiration. At this stage, the leaf flesh cells begin to dehydrate, and local necrosis occurs in the palisade tissue.
Obvious Symptom Characteristics (15-30 days)
The lesions expand to 3-5mm, forming red-brown concentric rings. A grayish-white mycelial layer appears on the back of the leaves, and the chlorophyll degradation rate can reach 60%, with a significant decrease in photosynthetic efficiency.
Outbreak Period Characteristics (30 days+)
The lesions connect to form V-shaped necrotic areas, conidiomata break through the cuticle, and the spore production per leaf can reach 10^4/cm². At this time, the defoliation rate can reach 70%, and the growth of new shoots stops.
Comprehensive Control Technology System
Three Principles of Pathogen Control
1. Implement the "Three Clean" measures in autumn and winter: remove diseased leaves, prune dense branches, and clear weeds in the planting area. 2. Spray lime sulfur (3-5 degrees Baume) in early spring to seal the overwintering pathogen sources. 3. Transplanted seedlings must be treated with a 50% carbendazim 500x solution for root dipping.
Four-season Osmanthus Leaf Blight and Its Control
Five Elements of Cultivation Management
• Establish a slightly acidic soil environment with a pH of 6.0-6.5. • Maintain a ventilation spacing of 1.5-2m between plants. • Implement drip irrigation technology to control air humidity below 75%. • Apply phosphorus and potassium fertilizers (N:P:K=1:1.5:2). • Loosen the soil to a depth of 15-20cm monthly.
Chemical Control Precision Plan
In the early stage of the disease, alternate the use of: • 25% azoxystrobin suspension concentrate 1500x solution (systemic therapy) • 80% mancozeb wettable powder 600x solution (protectant). In the peak period, use compound preparations: benomyl + propiconazole (1:1) 2000x solution, spray every 10 days, for 3 consecutive times.
By adopting a strategy of "prevention-oriented, comprehensive control" and implementing precise prevention and control measures according to the phenological period, the incidence of leaf blight can be controlled below 5%. It is recommended to establish a disease monitoring record, recording the time of each application, the type of pesticide used, and meteorological data, providing a scientific basis for sustainable management.