Home › Nursery Stock › Article

Symptom Identification and Control Methods for Azalea Leaf Spot Disease

Nursery Stock 0 views
Azalea leaf spot disease, also called brown spot disease, is a common and frequently occurring leaf spot disease of azaleas. After infection, black spots form on the leaves, which gradually dry up and fall off until the plant dies. The disease mainly harms azalea leaves and is caused by infection with the fungus Cercospora rhododendri. The pathogen first appears as several small brown dots, and as these dots continue to expand, the lesions connect with each other to form patches, producing grayish-brown mold hyphae. The affected leaves begin at the petiole, turn from green to brownish-yellow, and drop early. In severe cases, it affects the growth and development and ornamental value of azaleas. The pathogen overwinters on leaves or diseased plants,

Azalea leaf spot disease, also called brown spot disease, is a common and frequently occurring leaf spot disease of azaleas. After infection, black spots form on the leaves, which gradually dry up and fall off until the plant dies. The disease mainly harms azalea leaves and is caused by infection with the fungus Cercospora rhododendri. The pathogen first appears as several small brown dots, and as these dots continue to expand, the lesions connect with each other to form patches, producing grayish-brown mold hyphae. The affected leaves begin at the petiole, turn from green to brownish-yellow, and drop early. In severe cases, it affects the growth and development and ornamental value of azaleas. The pathogen overwinters on leaves or diseased plants, and spores are spread by wind.

The peak period of this disease is generally in hot and humid seasons, and it also occurs in greenhouses in winter. Generally, weakly growing plants, small seedlings, lower leaves, plants with poor ventilation, and Belgian azaleas (compared with Rhododendron mucronatum) are more severely affected. According to the patterns of occurrence, the following control measures can be taken:

(1) Strengthen cultivation management. For potted azaleas, use leaf mold soil as the potting medium, keep the pH of irrigation water between 4.5 and 6.5, water the substrate based on the principle of drying before wetting, and frequently apply some decomposed dilute organic liquid fertilizer to promote vigorous plant growth and thick leaves with improved resistance. Potted azaleas should be placed in a ventilated area, and in summer they should be shaded, protected from moisture, and protected from waterlogging. Diseased leaves should be promptly removed and burned, and attention should be paid to selecting disease-resistant varieties while strengthening plant pest and disease quarantine work.

(2) Chemical control: After flowering, promptly spray 70% thiophanate-methyl wettable powder at 800 times dilution or 50% carbendazim at 300 times dilution. In addition, sprays can be applied regularly for prevention. Protective fungicides and fungicides can be mixed and applied; for example, alternating Bailian plus M Daisan 45 with copper hydroxide can achieve good results, or use 1:1:150 Bordeaux mixture sprayed once a week for 2 consecutive applications; once the rainy season begins, spray 1:1:100 Bordeaux mixture once every 10 days for 3 to 4 consecutive applications.

Related Articles