Comprehensive control measures for common diseases of rhododendron
The main diseases of rhododendron are root rot, brown spot, black spot, leaf blight, iron deficiency chlorosis and so on.
After the rhododendron suffered from root rot, the growth was weak, the leaves wilted and withered, the surface of the root system appeared water-stained brown fields, serious soft rot, gradually rotted and peeled, and the xylem blackened. The disease is most likely to occur in an environment with high temperature and high humidity.
The prevention and cure method is to strictly disinfect the cultivated soil before turning the basin, and keep the soil loose and moist, make it have good permeability and avoid stagnant water. If the plant is found to be sick, the diseased plant and basin soil should be dealt with in time. During treatment, the diseased plant can be eluted with 0.1% potassium permanganate aqueous solution or 2% ferrous sulfate, then rinsed with clean water and put on the basin again. Use 70% topazine wettable powder plus 1000. It can be cured by spraying the basin soil with a solution made of double water.
Brown spot is a major disease of rhododendron. At the beginning of the disease, small brown spots appeared on the leaf surface, which gradually developed into irregular spots, and many black or grayish brown spots were produced on the disease spots, which made the damaged leaves yellow and fall off, affecting the flowering of the current year and the development of flower buds in the coming year. This disease often occurs during the rainy season when the humidity is high.
The treatment method is to pay attention to make the plant ventilated and transparent, not to make the humidity too high, and to increase the application of organic fertilizer and nitrogen, phosphorus and potassium mixed fertilizer to enhance the plant resistance to infection and growth. If diseased leaves are found, they should be removed in time and burned centrally. At the initial stage of the disease, 0.5% Bordeaux solution or 0.4 Baume stone sulfur agent was sprayed, and 4% flour was added to increase the adhesion. Leaf spot and black spot can also be treated with the same method.
Iron deficiency chlorosis often occurs in alkaline soil areas, when the disease is mild, only the plant late green phenomenon; in severe cases, the leaf tissue can all turn yellow and the leaf edge scorched. When the disease occurs, it is most obvious in the leaves of the top tip of the plant, which is generally caused by internal iron deficiency.
The control method is to change the property of iron deficiency in soil and reduce soil alkalinity. Apply more organic fertilizer to transform clayey soil. 0.2%-0.3% ferrous sulfate liquid can be directly sprayed on iron-deficient plants. You can also poke several holes about 15 cm deep in the soil around the plant with chopsticks and slowly inject them with liquid ferrous sulfate solution at 1:30 to fill the holes to increase soil acidity and reduce alkalinity.
The incidence and environmental conditions of rhododendron black spot are similar to those of brown spot, and similar methods can be used for prevention and control.
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The crown net bug of rhododendron
Also known as pear net bug, pear net bug, flower belongs to Hemiptera, Pentatomidae. All over the country. With nymphs, adults harm rhododendron, rose, camellia, Michelia, jasmine, wax plum, wisteria and other potted flowers and trees. For the harmful adults and nymphs are clustered on the back of the leaves to suck juice, and the back of the injured leaves looks like a black sticky substance that has been splashed. This feature can be easily distinguished from other piercing pests. The whole injured leaf is yellowish yellow on the back, and many pale spots are formed on the front. When the damage is serious, the spots become patches, and even the whole leaf is chlorotic.
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Control measures of common diseases of rhododendron
The common diseases and control measures of rhododendron can be classified into the following categories: 1. Symptoms of Botrytis cinerea the disease occurs in the leaves and flowers of rhododendrons. Freezing injury is often the cause of leaf disease. In spring, cuckoos cultivated indoors and outdoors are often infected with Botrytis cinerea. In the early stage of the disease, necrotic spots appeared on the petals, expanded rapidly, and connected to each other to form large disease spots. Under the condition of high humidity, the disease produces a large number of gray conidium, hence the name Botrytis cinerea. Pathogenic Botrytis cinerea [Botrytisci]
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