How to control root rot of American ginseng?

Root rot is also one of the main diseases of American ginseng. People often see American ginseng plants growing normally in ginseng fields wither rapidly due to water loss. When the ginseng was dug up, almost all the ginseng roots rotted, leaving only a ginseng root connected with the ginseng stem and a black hollow root skin. Root rot often occurs in pieces, resulting in the death of ginseng seedlings in pieces and serious losses to production.

(1) symptoms

At the beginning of the disease, light brown spots appeared on the reed head of ginseng root, and then spread to the base of stem, which withered the aboveground part and then spread down to the whole root. If the disease begins below the taproot, and the epidermis of the root surface is brown spots, then brown wet rot appears, it can quickly develop to the upper part of the root and penetrate into the internal tissue of the ginseng root, so that the ginseng root rot as a whole, showing black wet rot, leaving only empty shells. In the early stage of impregnation, there were no obvious symptoms in the aboveground parts, and the leaves faded and turned yellow in the later stage, wilting and turning yellow. Especially in July and August, when the temperature is still warm and the local humidity is high, the onset will be quick.

Infected plants can survive the winter in the late growth stage, but they can't emerge in the next year, or die soon after emergence. There are two differences between root rot and rust rot: ① There are obvious protruding edges at the junction of healthy and susceptible parts of rust rot, but root rot does not. ② The roots of ginseng rot quickly and wet rot after infection, while the rust rot is only dry on the surface and will not wet rot (Figure 37).

Fig. 37 Symptoms of root rot

(2) the cause of the disease

The pathogenic bacteria are Fusarium and Fusarium, which are abundant in soil, with developed hyphae, clustered conidia, colorless, single branch and terminal conidia. Fusarium is widely distributed in various types of soil, is a rhizobacteria, can cause many plant diseases, and is parasitic saprophytic with strong saprophytic ability. Fusarium can produce chlamydospores with strong resistance and can survive in soil for a long time. Root rot mainly occurs in the high temperature and rainy season from July to August, and it is easy to spread when the soil moisture is high. Rotten ginseng roots and the surrounding soil become the center of disease transmission.

(3) Prevention and control methods

① Apply fully decomposed organic fertilizer, increase phosphorus and potassium fertilizer, and decrease nitrogen fertilizer. Prevent excessive moisture in the soil of ginseng bed. ② Soil treatment: The field experiment proves that the soil fumigation effect is good, but the operation is complicated, the time is not well controlled or the fumigant is not fully released, which will cause harm to seeds and ginseng seedlings. In addition, 50% carbendazim wettable powder 15 ~ 20g per square meter can be used for soil disinfection, which can play a certain control effect. (3) Prevention and control of diseases in the growing period, that is, the diseased plants should be pulled out immediately when found, and the soil around the disease area should be watered with limewater, carbendazim and other liquid medicines to control the infection of germs to a minimum. Luheng 1 has a strong killing effect on soil fungi, especially Fusarium, Pythium, Fusarium oxysporum and Rhizoctonia. It can be used before planting and during the growth period of ginseng. The dosage per square meter is 1 g. Dissolve the pesticide in 3000 grams of water and pour it on the soil of 1 m2. When you make a cup, you can stir it evenly with a rake. The application of Ji 'an Ginseng Research Institute in the old ginseng field showed that the emergence rate of American ginseng was increased by 18% ~ 20%, and the survival rate of seedlings was increased by 14% ~ 15%. The experimental results of Jilin Agricultural University and Fusong Ginseng Research Institute are the same, and the control effect on root rot of American ginseng is obvious. Luheng 1 is a new soil fungicide with high efficiency, low toxicity and broad spectrum, which is worth popularizing.