Common diseases of cannabis include brown spot, Sclerotinia and white star disease. Today, let's talk about the first three common diseases. The occurrence of cannabis disease seriously affects the yield of cannabis, which needs to be paid great attention to by growers.
1. Hemp brown spot (hemp spot). Most of them occur on the old leaves, and dark brown spots appear on the surface of the first leaves. Later, the spots expand into a circle or near circle, the central part becomes light brown, the surrounding is pale yellow, and gray molds are dense on the back. The disease mostly occurs in July, and early defoliation is formed when the damage is serious.
Control methods: the combination of nitrogen, phosphorus and potassium fertilizer can enhance the disease resistance of hemp plants; Spray Bordeaux liquid 2-3 times when onset.
2. Cannabis Sclerotinia. It can occur in the whole growth period, and it occurs quickly under the condition of high temperature and humidity. Generally, when the seedling height is 30cm, gray black irregular disease spots occur at 10cm away from the ground, gradually expand and densely grow black gray molds, and the seedlings break and die here. When the hemp plant grows to more than 1m, irregular yellowish white spots appear on the leaves, on which there are many black mouse excrement like sclerotia.
Control methods: uprooting diseased plants and burning grass; Spray Bordeaux liquid 2-3 times in the early stage of onset.
3. Cannabis white spot disease. The disease occurs in leaves. There are small yellowish white or yellowish brown spots on the surface of the first diseased leaf along the vein, oval or triangular, about 1mm long. After that, the lesion expanded and connected with the adjacent lesion to form a score of 4-8 × 3-5mm lesion. The center of the lesion becomes black or grayish white powder, and the surrounding part is grayish brown or yellowish brown. Generally, the planting land with more fertilization and cloudy and wet is seriously affected. When the damage is serious, the leaves fall early, the growth is blocked, and the yield is affected.
Control method: remove the diseased leaves and burn them; Pay attention to drainage; Spray Bordeaux liquid 2-3 times in the early stage of serious illness.