The use of slope dry land, foothills, and cultivation of Shatian pomelo in front of houses are a good way for farmers to get rich. However, in the cultivation process of Sha Tin, it is prone to ulcer disease and care should be taken to prevent it. Shatian pomelo canker is a bacterial disease. The vectors are mainly wind and rain and insects. Germs often overwinter on diseased spots. They begin to breed in April and are infested by grapefruit trees from May to September, especially in the high-temperature and rainy season of July to September. The diseases are most serious. The main damage is the leaves, shoots, and fruits. The damaged leaves initially appear as oil-impregnated yellow or dark-yellow dots of the size of the needle, and later the dots gradually expand into round spots. The lesion penetrated the leaves on both sides of the surface, and the surface was corked, rough, gray-brown, water-stained or oil-immersed at the edges, surrounded by yellow haloes, and the central depression became crater-like at the later stage of the lesion. The shape of the lesion on the fruit is similar to that on the leaf, but the degree of corkification on the surface is not high, and the lesion on the new shoot is often more prominent than on the leaf. Control methods: 1. Select disease-free seedlings for planting. If the seedlings are sick, cut the diseased part before planting, and then use 1:1:100 times Bordeaux liquid to dip the leaves and plant them. 2. In orchards and nurseries, it is necessary to thoroughly clean the garden in the winter, collect fallen leaves, eradicate weeds, cut sick leaves, and burn them together. 3. Avoid partial application of nitrogen fertilizer, nitrogen, phosphorus and potassium should be reasonable with the application. In April-September, more phosphorus and potassium fertilizers are needed to make the pomelo tree grow robustly and enhance its disease resistance. 4. Do a good job of preventing disease and protecting the tip during the shoot growth period, such as controlling the tip and controlling the leafminer. 5. In the spring, summer and autumn shoots, when the leaves are not expanded, each spray once, after flowering and after each wind and rain, each spray once, the agent can be 1:1:100 times more Bordeaux or copper soap , Or 50% dexamethasone 800 times or farmland streptomycin. If these drugs are used alternately, the effect will be better.
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