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What are the control methods for tea plant purple root rot?

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Distribution and symptoms: It is found in all tea-producing areas, but occurs fairly commonly in North China and East China. This disease mainly occurs at the seedling stage and the mature plant stage, damaging the roots or the root collar. First the fibrous roots rot, turning brown or dark brown, then it spreads to the lateral roots, which after rotting turn purplish brown. The surface of the lesions is covered with purplish brown thread-like matter, and on the surface of the diseased roots there are hemispherical granular sclerotia. The base of the small stem plus cm is often surrounded by purplish red mycelium, soft in texture; it peels off easily, and the root cortex also peels off easily. In severe cases the aboveground part wilts, new shoot sprouting decreases, and the diseased plant dies. Occurrence pattern

Distribution and symptoms: It is found in all tea-producing areas, but occurs fairly commonly in North China and East China. This disease mainly occurs at the seedling stage and the mature plant stage, damaging the roots or the root collar. First the fibrous roots rot, turning brown or dark brown, then it spreads to the lateral roots, which after rotting turn purplish brown. The surface of the lesions is covered with purplish brown thread-like matter, and on the surface of the diseased roots there are hemispherical granular sclerotia. The base of the small stem plus cm is often surrounded by purplish red mycelium, soft in texture; it peels off easily, and the root cortex also peels off easily. In severe cases the aboveground part wilts, new shoot sprouting decreases, and the diseased plant dies.

Occurrence pattern: Generally, the disease is more severe at the turn of spring and summer or the turn of summer and autumn when it is hot and rainy. Tea gardens with a high groundwater table, poor drainage, or excessively dry soil are prone to the disease. This pathogen can survive in the soil for many years and spreads with farming operations, rain, soil-dwelling pests and root contact, and can also be spread over long distances when infected seedlings and soil are transported. Continuous cropping and a previous crop susceptible to the disease also make the disease more likely.

Control methods:

Select sterile, healthy seedlings. When diseased seedlings are found, dig them out promptly and burn them, wash the tools after use, then soak the remaining healthy seedlings in a 20% lime emulsion for 1 hour, or soak the roots in a 50% carbendazim 1000-fold dilution for half an hour before planting. Tea gardens with poor drainage and a high water table should pay attention to drainage, and drainage ditches should be dug before flooding. Land where sweet potato, potato and fruit trees were previously grown and where this disease has occurred should be disinfected with 70% quintozene, using 2.5 kg per mu mixed with fine soil for soil disinfection, or the soil should be drenched with a 30-fold dilution of formalin. In the early stage of the disease, drench the root collar with a 1000-fold dilution of potassium permanganate or carbendazim.

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