How to prevent and control lotus root rot? Prevention is key
Rot is a relatively common disease on lotus root, occurring to varying degrees every year. Wuhan has a large lotus root planting area, and local lotus root rot occurs severely. Lotus root seeds in most regions are introduced from Wuhan, so in recent years lotus root rot has occurred severely in lotus fields in some areas. After the disease occurs, the plant's vascular bundles turn brown...
Rot is a relatively common disease on lotus root, occurring to varying degrees every year. Wuhan has a large lotus root planting area, and local lotus root rot occurs severely. Lotus root seeds in most regions are introduced from Wuhan, so in recent years lotus root rot has occurred severely in lotus fields in some areas. After the disease occurs, the plant's vascular bundles turn brown and rot, so strip-shaped rot appears on the lotus root segments. In fields with many years of continuous cropping, pathogens accumulate in the field, and the disease is severe. This disease mainly damages the underground parts of lotus root, and after pesticide application the chemicals are difficult to reach the diseased parts directly, making control relatively difficult. Adopting crop rotation and carefully selecting lotus root seeds before planting are the most effective measures to control this disease. After the disease occurs, diseased plants should be pulled out, and the holes should be sealed with quicklime to prevent the pathogens from spreading outward. Spraying carbendazim, thiophanate-methyl and other chemicals does not have a very good therapeutic effect on diseased plants, but it can protect healthy plants.
It is understood that rot mainly damages the underground stems of lotus root, causing brown rot, and the disease leads to withering of the aboveground parts. At the beginning of the disease, the leaf color becomes lighter, the leaf margins dry up and turn brown, and curl downward, and finally the entire leaf dries up and turns brown. The leaf stalks also shrink and die from top to bottom, and after the old leaves are affected, the disease gradually spreads to new leaves. When the underground stems are damaged, the early symptoms are not obvious. When the diseased stems are cut open, the internal vascular bundles first turn light brown to brown, and afterward brown or purple-black lesions appear on the outside. Finally the entire stem rots, causing the aboveground parts to die, and in severe cases the whole field turns yellow and withered.
This disease is caused by infection by multiple pathogens. The pathogens overwinter in seed lotus roots and lotus field soil, spread through seed seedlings and soil, and can also enter lotus fields through irrigation water and spread to surrounding lotus fields. The disease begins in early June, with peak occurrence from mid-July to early August. The pathogens infect quickly at 23-30°C and under conditions of continuous rain, insufficient sunlight or frequent storms. The disease is severe in lotus fields with high acidity, water temperature above 35°C, severe damage by the lotus root grub, or application of undecomposed organic fertilizer or excessive nitrogen fertilizer.
To prevent and control lotus root rot, first, select healthy disease-free seed lotus roots, spray with 800 times solution of 70% thiophanate-methyl wettable powder or 75% chlorothalonil wettable powder or 50% carbendazim wettable powder, cover with film and keep sealed for 24 hours, then dry and plant. Second, carry out reasonable crop rotation, preferably in the form of lotus root, rice and winter flooding rotation or lotus root and Alisma plantago-aquatica rotation. Third, before planting, deeply plow the lotus field, dry it appropriately, and broadcast 200-250 kg of quicklime per mu. Fourth, strengthen fertilizer and water management, apply sufficient decomposed organic fertilizer, apply nitrogen, phosphorus and potassium fertilizers in combination, apply fertilizer at the right time and in the right amount during the growing period, and do not apply excessive nitrogen fertilizer; manage water scientifically, keep the depth moderate, and use water to regulate temperature and fertilizer, preventing increased disease incidence caused by excessively high water temperature or long-term deep irrigation. Fifth, chemical control: spray with 600 times solution of 50% carbendazim wettable powder or 700 times solution of 70% thiophanate-methyl wettable powder. At the same time, mix 500 g of 50% carbendazim wettable powder plus 75% chlorothalonil wettable powder per mu with 30 kg of fine soil, pile and cover for 3-4 hours, then broadcast, and keep a shallow water layer in the field. The two methods can be carried out at the same time, once every 7 days, for 2-3 consecutive treatments.