feng shui
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Cactus canker in a large area is probably caused by a large number of bacteria invasion caused by improper watering and fertilization. Cactus requires a dry environment and is afraid of water accumulation in the basin. Usually, the potted soil should be kept "dry and wet" and watered every five to ten days. When watering, don't pour it directly on the pulp. When the temperature is low, water should be poured every 10- 15 days to keep the soil dry. It is best to water it with dry water. Watering time should be carried out in sunny morning. Don't spray water on the surface of the sphere on cloudy days or sunny days, but don't see direct light before the water on the sphere evaporates, so as to avoid the condensation of water droplets burning the sphere and causing diseases. Fertilize once every one or two months. When the soil in the basin is dry, it must be fertilized. Pay more attention, the fertilizer solution can't touch the ball. If you accidentally touch it, you should immediately spray it with clear water, otherwise it will easily lead to infection.
In high temperature and poor ventilation environment, pests and diseases are prone to occur.
1 The pathogen Fusarium oxysporum Schlecht, also known as Fusarium oxysporum, belongs to Hemiptera subfamily. Conidiophore is clustered in broom-like branches, with round bottle-shaped petioles at the top of the branches and conidia on them. There are two types of conidia: the megaspore is sickle-shaped and colorless, with 3-5 septa, and most of them have 3 septa, with the size of 19-50× 2.5-5 (micron); Microspores are ovoid to kidney-shaped, unicellular or bicellular, colorless, with a size of 5-26× 2-4.5 (micron). The pathogen can produce thick-walled spores, which are terminal or symbiotic, spherical and thick-walled, with a diameter of 5-15 μ m.
The main symptom is stem injury. At the beginning, pale yellow to yellowish brown water-stained amorphous chlorosis spots appeared in the stem nodes, and the boundary of the diseased part was not obvious. The lesion became reddish brown after enlargement, and the affected part gradually softened and rotted, leaving only a layer of dry skin or stem pith. Finally, the whole plant rotted and withered, and some stem nodes near the soil rotted rapidly. When the humidity is high, powdery mildew can appear in the affected part, that is, conidia cluster and conidia.
Transmission route and pathogenic conditions: hyphae and chlamydospores overwinter on diseased tissues or diseased residues in fallen soil, and conidia are produced in the second year, which are splashed by rain and spread from the wound to cause disease, and conidia are continuously produced at the diseased site for reinfection. Continuous rainfall in early spring and early summer, warm days and cool nights are conducive to the onset. Low-lying water in the planting area, closed and high humidity in the field, wounds caused by slugs on the stems, or incomplete application of soil and miscellaneous fertilizers will aggravate the disease.
4 Control method (1) Increase the application amount of phosphorus and potassium fertilizer to avoid the application of incomplete decomposed soil miscellaneous fertilizer. (2) Dig out the diseased stems in time, thoroughly remove the sick and disabled objects and burn them. (3) Mildly diseased stems can be cut off with a knife, and the incision can be coated with 50% carbendazim or 65,438+000 times of 25% benadryl wettable powder or 65,438+000 times of 40% polysulfide suspension. (4) At the early stage of the disease, 300 times of 10% water solution of shuangxiaoling or 800 times of 65% Dixon wettable powder and 600 times of 50% carbendazim wettable powder were sprayed at the disease site. 1 time and * * * 2-3 times as the case may be.