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Lotus root is one of the most economically valuable aquatic crops in China, playing a crucial role in rural economies. Over the past few years, the growing demand for lotus root has led to a steady expansion in its cultivation area, making it a key industry in many regions. However, the increasing occurrence of pests and diseases has become a major challenge, threatening the sustainable development of lotus root farming. This article outlines effective strategies for preventing and managing some of the most common pests and diseases affecting lotus root.
First, **lotus root rot disease** (also known as "Scorpion") is a serious issue. The symptoms start with pale green leaves that gradually dry from the edges, followed by leaf curling and wilting. The stem tips may also become curved and dry, leading to widespread yellowing of the field. To prevent this, farmers should implement a 2-3 year crop rotation in heavily affected areas. Applying 70% thiophanate-methyl at 1000 times dilution or 75% chlorothalonil at 800 times, and covering the field with agricultural film for 24 hours before planting can help reduce the risk. Before planting, deep plowing combined with 100 kg of lime per acre is recommended. When the disease occurs, mixing 0.5 kg of 75% chlorothalonil with 30 kg of dry soil and applying it to shallow water can be effective. Since the pathogen resides in the underground stem, it’s essential to spray the lower part of the plant and maintain only 3–5 cm of water depth.
Second, **black spot disease** (also called brown leaf disease or leaf spot) begins with small yellow-brown spots on the leaves, which later develop into ring-like lesions, causing the leaves to dry out. To manage this, farmers should increase phosphorus and potassium fertilizers while avoiding excessive nitrogen. Infected leaves should be removed and burned during winter. In early stages, spraying 70% carbendazim at 1000 times or 65% mancozeb at 600 times is effective. Alternatively, a Bordeaux mixture at 1:1:166–200 times can be used, applied every 10 days for 2–3 treatments.
Third, **lotus root virus disease** causes irregular brown spots on the leaves and dark brown streaks on the rhizome. Prevention involves selecting resistant varieties and controlling aphids, which are the main vectors of the virus. Early application of 1.5% diseased plant disease emulsion diluted to 1000 times can help manage the infection.
Fourth, **leaf yellowing and wilting** is often caused by environmental stressors such as polluted water, oil spills, or soapy water. Lotus roots are highly sensitive to herbicides, so it's important to keep the fields clean and avoid chemical contamination. Proper water management is crucial to prevent this condition.
Finally, common pests like **roundworms**, **Spodoptera litura** (cutworms), and **moths** damage the leaves and buds. These can be controlled using 90% trichlorfon at 800–1000 times dilution or 40% dimethoate at 2000 times. For root-feeding insects, applying lime at 10–15 kg per mu can effectively eliminate them.
By implementing these preventive and control measures, farmers can significantly improve the health and yield of their lotus root crops, ensuring long-term profitability and sustainability in the industry.