Pyria yellow leaf disease is caused by iron deficiency, which is mainly due to insufficient supply of divalent iron in the soil. The disease of the leaves occurs frequently in Xindiaowang. The symptoms begin with the tender leaves at the tip of the shoot. In the early stage, the leaf chlorosis became yellow, the veins on the veins and veins remained green on both sides, and the leaves showed a green reticular pattern, and the diseased leaves became smaller. As the disease progresses, the degree of chlorosis gradually increases, resulting in yellow-white leaves. In the late stage, the brown spots began to appear on the edge of the leaves. When the leaves were severe, the whole leaves scorch off and the top buds died. On specific shoots, with the increase in the degree of damage, the leaves gradually dipped and fell off from the top, and the new shoots gradually turned brown from top to bottom. When it is serious, the yellow leaves of the upper part of the new garden are seen from afar, and there are many bare shoots on the top of the tree. Heavy saline soil, low-lying land, high groundwater level, soil viscosity, poor drainage, and regular irrigation can all induce and aggravate the disease.
Control methods: (1) Increase organic fertilizers, intercropping green manure crops, improving soils, increasing soil organic matter content, and promoting conversion of trivalent iron to divalent iron in soil. (2) Saline-alkali pear orchard is washed with water in a timely manner in spring to remove salt water and control salt levels. (3) buried iron fertilizer. Severe yellow leaf disease orchards can be combined with fertilization and application of divalent iron salts in autumn. According to the age of the tree, it is generally 0.5-2 kilograms per ferrous sulfate or chelated iron. It is best to mix the iron fertilizer and organic fertilizer in the ratio of 1:5. The application of iron fertilizer buried for a period of up to 2 years. (4) Spray iron fertilizer. Before the pears germinate, apply 0.3-0.5% ferrous sulfate solution to the branches, or spray the ferrous sulfate, copper sulfate, quicklime, and water in a ratio of 1:1:2.5:300. There is a significant role in controlling disease occurrence, but the effective period is shorter. After the yellow leaf disease is found during the growth period, it can be treated with iron fertilizer in time, usually once every 7-10 days until the leaves turn green. Applicable agents are 200-300 times of available iron, 500-600 times of yellow leaf spirit, 200-300 times of ferrous sulfate, etc., and about 1% of urea can be properly added into the liquid during spraying.
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