Identification and Control of several Common fungal Diseases in Rhododendron

Among the common rhododendron diseases, the main fungal diseases are rhododendron powdery mildew, rust, gray spot, blight, cake leaf disease and so on.

(1) the main differences of the following diseases are: 1. Rhododendron powdery mildew: it usually occurs in the middle and later stage of growth, which at first fades to green spot, then grows white mycelium layer, produces a large number of white powdery conidium layer, and later becomes grayish brown. Rhododendron rust: transparent golden or light brown spores occurred on the back of the leaves in the early stage, and yellowish brown or red leaf spots appeared in the middle and later stages. 3. Cuckoo gray spot (anthracnose): large leaf spot, silver gray on the front, dark brown on the edge, light brown on the back, small black on the upper side. Most of them occur in the parts of sunburn and frost injury. 4. Rhododendron blight: in general, the base of the main root turns brown and rotten, the apical buds and leaves turn brown, bend and droop; twigs ulcer and wrinkle, often "dead top". After a circle of fester at the base of the stem, the upper branches and leaves withered. 5. Azalea cake leaf disease (leaf swelling disease): injured young leaves, new shoots, flower buds, such as hypertrophy and swelling, often cause gall tumor (cross-cut 10Mel 20mm) light white, heavy leaf deformity, new shoots clump, bud into a ball, flowers into waxy gall tumor, disease surface gray-white or pink.

(2) Prevention and control of rhododendron fungal diseases: the occurrence conditions of rhododendron fungal diseases are high humidity, canopy, lack of light, frostbite, sunburn and so on. The second is the accumulation of continuous cultivation bacteria year by year, and partial application of nitrogen fertilizer, watering too frequently. The main control methods in cultivation are ① to improve the ecological environment of rhododendron, strengthen ventilation and light transmission, reduce trauma and change basin soil. Apply compound fertilizer. Cut off the diseased and residual branches in time. ② chemical control: for rhododendron powdery mildew and rust, use 1500 times solution of 25% powder, or 1000 times solution of topiramine wettable powder. Control of cuckoo gray spot: 1000-fold solution of 70% methyl topiramate, or 600-fold solution of 75% chlorothalonil. Prevention and control of rhododendron blight: use 1% Bordeaux solution, or spray 0.1% murine 0.2% copper sulfate solution. You can also use 600-fold solution of Trichoderma. Control with 600-fold solution of chlorothalonil. Prevention and treatment of rhododendron cake leaf disease: spray with 150 times equal volume Bordeaux solution or 0.5 degree stone sulfur mixture.