Symptoms: white powdery mildew layer appears on the back of the leaves, and gradually turns into light yellow spots under the leaves. After that, the leaves shrink, the diseased leaves wither and fall off, which will affect the flowering seriously. When the sun is insufficient, the air humidity is high and the drainage is poor, the disease is serious.
Prevention and control: apply fertilizer reasonably, pay attention to watering and drainage to avoid excessive humidity and drought, cut off the diseased branches and leaves, burn them in time, and create clean growth conditions for the plants.
Symptoms: the lesion appears on both sides of the front and back of the leaf, nearly round, brown to dark brown or dark grayish brown in the middle of the lesion, dark brown or near black thin line circle around the edge, light brown on the back of the leaf, and light olive mildew on both sides of the lesion. After the disease spots fused, the leaves turned brown and yellow or the plants died.
Prevention and control: the basin should be changed every spring and the diseased leaves should be removed in time. Spray prevention and treatment at the early stage of the disease.
Symptoms: there are a lot of small orange spots on the front of the leaves, then yellow spots on the back of the leaves, and then white spots on the front of the leaves. It is easy to get sick in rainy season, causing serious damage.
Prevention and control: eliminate the diseased branches and leaves and burn them intensively. After the plant sprouts, 800 times of mancozeb WP or 800 times of 15% Triadimefon WP can be used for spraying.
Symptoms: when serious, the leaves are eaten up, leaving only veins and petioles, which seriously affect the growth of plants and even cause death.
Prevention and control: from July to August, cocoons were collected on the affected branches and burned intensively. Chemical control usually occurs before the 3 instar larvae, when the lower epidermis and mesophyll of the leaves are eaten up, forming transparent spots, and when small patches are connected into blocks, spray 90% crystals of 1000 fold liquid of DTaP.
Symptoms: generally, the damage is rampant when the temperature is high and dry in July and August, and the leaves are perforated or only veins are left.
Control: use black light to trap adult worms, and spray 80% dichlorvos EC 1000 times at the initial stage of larvae. Spray should be sprayed to the top of the crown.
