tree Peony leaf spot is a common fungal disease in rockii tree peony cultivation, mainly caused by high temperature and humid weather leading to bacterial infection. The following is a comprehensive prevention and control guide for the disease:
I. Symptom identification
- Initial symptoms:
Small brown or dark brown round or oval spots appear on the leaves, and the edges may be purple-red or dark brown.
-The spots gradually expand (2~10mm in diameter), the central color becomes lighter, and may break and perforate in the later stage. - Late symptoms:
The spots are connected, causing the leaves to turn yellow and fall early. In severe cases, the entire plant leaves fall off, weakening the growth of the plant and affecting flowering.
In a humid environment, a gray-black mold layer (conidia of the pathogen) can be seen on the back of the spots.
II. Disease conditions
High-incidence season: late spring to autumn (warm and rainy, humidity>80% prone to outbreak).
Transmission route: wind and rain, irrigation water splashing, and diseased leaves remaining in the soil overwintering.
Causes: overcrowding, poor ventilation, excessive nitrogen fertilizer, and poor soil drainage.
III. Prevention and control measures
- Agricultural prevention and control
Clean up the source of disease:
Remove diseased leaves and destroy them in time, and completely remove fallen leaves in autumn to reduce the source of overwintering fungi.
Improve the environment:
-Avoid dense planting, ensure ventilation and light transmission; avoid long-term water exposure of leaves (drip irrigation or morning watering is recommended). - Chemical control
Preventive medication:
Spray 1:1:100 Bordeaux mixture or 70% mancozeb 600 times solution in the spring budding period, once every 10-15 days.
Therapeutic medication:
In the early stage of the disease, use **50% carbendazim 800 times solution, 25% azoxystrobin 1500 times solution or 10% difenoconazole 2000 times solution, alternately, 7-10 days apart, and spray 2-3 times in a row.
IV. Precautions
When spraying, cover the front and back of the leaves, and prevent in advance before the rainy season.
Leaf spot disease can be effectively controlled through comprehensive management. If the disease is severe, it needs to be cured by combining pruning (to improve ventilation) and soil disinfection (such as sun exposure or root irrigation with fungicides).
