Zhang Jianxin, Linyi City, Shandong Province, came to the telephone on August 4 to report that there are many local lotus roots in Shamian, where the petioles in the underwater part of the diseased plants are rotted, some underground stems are rotted, and decayed parts are striped. These ponds have been continuously cultivated for 6 years. After harvesting, they do not clean up the ponds. The low-lying ponds are seriously affected. According to Chen Fengren of Tuhe Township, Guanyun County, the telephone number of August 6 reported that there were more than 20 acres of shallow water scabs in the area. The scald spots were found in the upper petiole at the beginning of the disease. After the black rot, the leaves also had irregular brown spots. After enlargement, it was connected to a large spot, and finally the leaves died, and the diseased leaf rate reached 20%. They asked what kind of illness lotus had got and how to prevent it.
According to the preliminary diagnosis of Prof. Jiang Jiezeng of the Aquatic Vegetables Research Center of Yangzhou University, symptoms of underground stem rot and brown leaves withered in the lotus roots in these two regions are likely to be caused by corruption of lotus roots.
Jiang Jiezeng said that corruption is a relatively common disease on lotus roots and occurs every year to varying degrees. The planting area of ​​lotus root in Wuhan City is large, and the corruption of the local lotus root is serious. Most of the species in our province have been introduced from Wuhan. Therefore, in recent years, corruption in Putian has been serious in some areas of our province. After the onset of disease, the vascular bundle of the plant will turn brown and rot, resulting in strip rot on the septum. For many years, continuous cropping of field bacteria has accumulated and the disease has become severe. The disease is mainly harmful to the underground lotus root. It is difficult for the drug to reach the diseased part after application. The prevention and control are more difficult. Selecting the pods before rotation and before sowing is the most effective measure to prevent and treat the disease. After the onset of disease, the diseased plant should be removed and the hole should be sealed with quicklime to prevent the outbreak of germs. Spraying carbendazim, thiophanate-methyl and other drugs have no good treatment effect on the diseased plants, but they can protect the healthy plants.
It is understood that the corruption disease mainly damages the underground stems of lotus roots and causes brown rot. The disease causes the land to wilt. At the beginning of the disease, the leaf color became lighter, the leaf margin became brownish, and curled downwards. Finally, the whole leaf became brown and dry, and the petioles also shrank from top to bottom and gradually spread to the new leaf after old leaf lesions. The underground stem was damaged and the initial symptoms were not obvious. The vascular bundles in the cutaway stems first turned pale brown to brown, followed by brown or purple-black lesions on the outside. Finally, the whole stem rotted, causing the aerial parts to die. In severe cases, the whole field was yellow.
The disease is caused by a variety of bacterial infections. The pathogenic bacteria live in seed and earth fields in Putian and spread through seedlings and soil. They can also enter irrigation fields through irrigation water and spread to surrounding paddies. The onset began in early June, and it took place from mid-July to early August. The bacteria infested rapidly at 23-30°C with continuous rain, lack of sunlight, or frequent storms. Putian acidity is large, the water temperature is higher than 35°C, the weight of the rootworm is heavy, or the application of unfamiliar organic fertilizer and partial nitrogen fertilizer is heavy.
To prevent and treat spoilage of lotus root, one is to use a robust and disease-free seedling, spray with 70% thiophanate-methyl WP or 75% chlorothalonil wettable powder or 50% carbendazim WP 800 times. Closed for 24 hours, dried and planted. The second is a reasonable rotation, with lotus, rice, winter rotation or lotus, Alisma rotation in the best form. Third, before planting, deep-turning paddy field, appropriate drying, 200-250 kilograms of lime per acre. The fourth is to strengthen fertilizer and water management, apply sufficient organic fertilizer, combined application of nitrogen, phosphorus and potassium fertilizers, timely and appropriate fertilization in the growth phase, without partial nitrogen fertilizer application; scientific management of water, moderate depth, water thermoregulation, prevent excessive water temperature or long-term depth Irrigation worsens the incidence. The fifth is chemical control, sprayed with 50% carbendazim WP 600 times or 70% thiophanate WP 700 times. At the same time, use 50% carbendazim WP per acre plus 75% chlorothalonil WP 500 g mixed soil 30 kg, heap boring after 3-4 hours to spread, the field to maintain a shallow water layer. Both methods can be performed at the same time, once every 7 days, for 2-3 consecutive times.
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