Common Diseases and Control Methods of Peony
As a symbol of the fragrance of the nation, peonies hold an important place in courtyard planting. However, many flower enthusiasts often encounter disease problems during maintenance, which not only affects the health of the plant but also ruins the flowering effect. This article will systematically analyze the identification characteristics and control techniques of the four most common diseases of peonies, helping you create a healthy peony garden.
I. Leaf Spot Disease: The Killer of Peony Leaves
Symptom Identification and Pathogenesis
During the hot and humid season from June to August each year, needle-like brown spots first appear on the back of the leaves, and these spots develop into concentric ring-like lesions as the disease progresses. In severe cases, the lesions merge, causing the entire leaf to wither and the plant to shed leaves prematurely.
Comprehensive Control Plan
Prevention is the main strategy: immediately after flowering, spray a 1:1:100 Bordeaux mixture, and enhance ventilation by pruning dense branches. In the early stage of the disease, switch to a 70% methyl thiophanate solution diluted 800 times, focusing on spraying the back of the leaves.
II. Yellow Leaf Disease: A Warning of Nutritional Imbalance
Typical Symptoms
Yellowing first appears at the tips of old leaves and gradually spreads to new leaves, accompanied by slow growth and reduced flower bud differentiation. High soil pH values can cause iron absorption problems, leading to similar symptoms.
Accurate Fertilization Techniques
After flowering, apply phosphorus-potassium compound fertilizer and spray a mixture of 0.2% potassium dihydrogen phosphate and EDTA chelated iron on the leaves. It is recommended to conduct soil testing every two years to maintain a pH value between 6.5 and 7.0.
III. Sclerotinia Disease: The Crisis of Root and Stem Rot
Disease Development Process
In early spring, when the soil temperature rises, the pathogen invades the roots and stems through wounds, forming water-soaked rot spots. White mycelium can be seen in the affected area, and black sclerotia are produced later, which can survive in the soil for 3-5 years.
Soil Treatment Points
Disinfect the soil with pentachloronitrobenzene before planting, and sprinkle lime (2kg/㎡) before the rainy season. Immediately remove infected plants and pour a 50% thiram solution (500 times diluted) into the affected area.
IV. Purple Fuzz Disease: The Hidden Killer of Roots
Typical Identification Features
The root surface is covered with a layer of purple-red mycelium, and the fibrous roots become linearly dry. The above-ground part shows symptoms similar to water deficiency, but these cannot be alleviated by watering, ultimately causing the entire plant to wilt.
New Biological Control Method
In the early stage of the disease, apply Trichoderma harzianum to the roots, and enhance resistance by applying decomposed organic fertilizer. In severely affected areas, practice crop rotation for more than 5 years to avoid consecutive planting, which can exacerbate the disease.
Caring for peonies should follow the principle of 'three parts planting, seven parts maintenance'. By regularly observing, scientifically fertilizing, properly pruning, and precisely using medications, disease occurrence can be effectively prevented. It is recommended to establish a maintenance log to record the time and control measures for each pest and disease occurrence, gradually forming an individualized peony care system. Mastering these techniques will ensure that your peonies bloom beautifully every year.