Occurrence and Control of main Diseases of Atractylodes macrocephala Koidz

Ningguo City, Anhui Province is the traditional main producing area of Atractylodes macrocephala Koidz, which has been planted for more than 40 years. It is deeply loved by customers all over the world because of its large, thick and good quality products. The average annual planting area of Atractylodes macrocephala Koidz is about 90 hectares and the output value is about 2 million yuan, which is one of the main sources of income for pharmaceutical farmers in our city. In recent years, with the continuous expansion of the planting area of Atractylodes macrocephala Koidz, the diseases of Atractylodes macrocephala Koidz showed a tendency to occur year by year, especially in the seedling stage, root rot and white silk disease of roots and stems in the adult stage, and the leaf spot blight had a high incidence and the most serious harm, which brought great economic losses to drug farmers.

I. occurrence regularity and harm characteristics

1. Blight: also known as stem rot blast, is the main disease of Atractylodes macrocephala at seedling stage. The pathogen is Rhizoctonia solanacearum, which overwinters with mycelium or sclerotia in the soil or host residue, and can saprophyte in the soil for 2-3 years. The hyphae can also be produced in the disease department, which quickly spread and harm the neighboring plants. The disease is a disease of low temperature and high humidity. In case of low temperature, overcast and rainy weather after sowing in early spring, the growth of seedlings is slow, the tissue is not corked, the disease resistance is weak, and it is easy to be infected. Ununearthed buds, seedlings and transplanted seedlings can be damaged, rotten buds and rotten seeds appear. After the seedlings were unearthed, water-stained dark brown disease spots appeared at the base of the young stem near the surface, and soon extended around the stem, and the stem necrosed and contracted into a linear "wire stem". The diseased part often adhered to the small soil granular brown sclerotia, the aboveground wilted, and the seedlings lodged and died. It often causes the death of the seedlings and leads to the destruction of the seeds. Wet leaves close to the ground can also be damaged, and the edges produce water-stained dark brown spots, which soon spread to the whole leaf.

2. Root rot: also known as dry rot, is one of the important diseases of Atractylodes macrocephala Koidz. Soil and seed-borne bacteria are the sources of infection of the disease. The decrease of disease resistance of seedlings caused by heat during storage is the main cause of the disease. When the soil is flooded, the soil is heavy, or the application of immature organic fertilizer, nematodes and underground pests cause poor root system development or wounds, it is very easy to be infected by bacteria. The pathogen requires high temperature, and the disease occurs suddenly when the temperature rises and turns sunny after continuous rain in the middle and later stages of plant growth. The disease generally begins in late April and is prevalent from June to August. The rate of diseased plants is about 20%, and the seriously diseased field can reach more than 60%. It gradually alleviated and stabilized in the late August. The symptom of the disease is that the fine roots of the rhizome turn brown and rot. Then spread to the upper fleshy rhizome and stem, showing dark brown sunken rotten spots, and the aboveground began to wilt. The vascular bundles showed obvious discoloration circle in the rhizome and stem cross-section. in the later stage, the rhizomes all turned into spongy black dry rot, and the plants died and were easy to be pulled out from the soil. The occurrence of dry rot, stem rot and wet rot is common in both new and old producing areas, which seriously affects the yield and quality.

3. White silk disease: commonly known as "rotten sugar", which harms the rhizome. Bacteria-carrying soil, fertilizer and planting are the sources of infection of the disease. In the early stage of the disease, re-infection was carried out by mycelium spread or sclerotia spread with water flow. The first diseased plants in the field were in late April, and the disease was at its peak from June to August. High temperature and heavy rain easily caused the epidemic. The incidence rate of general fields is about 15%, and that of seriously diseased fields is more than 20%. After August, the incidence decreased gradually, and the condition tended to be stable. The symptom is that the fibrous root and rhizome on the rhizome turn brown, the surface of the rhizome is covered with white hyphae, and milky white or light brown sclerotia can be seen inside the hyphae. Sometimes white hyphae and sclerotia can be seen on the surface of the soil around the base of the stem of diseased plants. With the development of the disease, the stems and leaves of the aboveground part of the diseased plant gradually withered, the underground rhizome began to rot, and the rotten rhizome was in the shape of "rotten potato".

4. Spot blight: the drug farmer called "iron leaf disease", which is an important leaf disease commonly occurred in Atractylodes macrocephala producing areas. The pathogen overwintered mainly by conidia and mycelium on the diseased remains and seeds, and became the source of primary infection in the following year. In the next spring, the conidia were released after meeting water droplets, and the primary infection was caused by stomatal invasion; new conidia were produced on the disease spot, which constantly caused re-infection and spread. Seed-borne bacteria cause long-distance transmission, and Rain Water splash is the main way of short-range transmission, insects and agricultural operations can also cause transmission. The disease occurred for a long time, and the epidemic needed high humidity. Most of the disease began in late April and flourished from June to August. Rain Water became more serious when the temperature rose and dropped greatly. The symptoms of the disease are primary yellow-green spots on the leaves, and then irregular shapes formed by polygonal veins, dark brown to black, gray-white in the center, and small upper black spots. In severe cases, the disease spots converge with each other and cover the whole leaves, showing iron black, and the stems and bracts also produce similar brown spots.

Second, prevention and control measures. Soil, planting, fertilizer and carrying bacteria in diseased body are the root causes of disease of Atractylodes macrocephala Koidz. Therefore, the prevention and control of diseases of Atractylodes macrocephala Koidz must adhere to the policy of "giving priority to prevention, prevention is more important than treatment, and comprehensive control". On the premise of soil disinfection and seed planting treatment, we should strengthen field cultivation management and improve plant disease resistance. it can restrain the occurrence of the disease; once the disease occurs, chemicals can be used to block the disease area, control the spread and spread of bacteria, and reduce the loss caused by the disease.

The main results are as follows: 1. Land selection and preparation: it is appropriate to choose the mountain area of raw wasteland or stopped planting Atractylodes macrocephala for more than 4 years, deep soil layer, south facing north, and well drained sandy loam soil as seedling and cultivation fields of Atractylodes macrocephala. The selected land is preferably sloping land with a slight slope to facilitate water permeability and drainage. The seedling land with a slope of 10-15 degrees is better than the barren shady slope wasteland or abandoned land, and the young leaves of Atractylodes macrocephala seedlings are too tender and weak in disease resistance. Winter ploughing should be carried out in time after the previous harvest, which is not only beneficial to soil ripening, but also reduce the harm of weeds, diseases and insect pests. Ploughing again with sufficient basic fertilizer before planting, fine crushing and leveling to make a bed according to the requirements of seedling raising or transplanting.

2. Soil disinfection: in order to effectively prevent the occurrence of diseases such as standing blight, before soil preparation, 50 kg of raw lime powder per mu is applied to seedling and cultivation land, and then ploughed and fine; before sowing and transplanting, 50% carbendazim or 50% carbendazim granules are used to treat the soil with 1-2 kg per mu; to avoid raising seedlings or planting in diseased soil.

3. Seed treatment: before sowing, select fresh, full and consistent disease-free seeds and soak them in 25-30 ℃ warm water for 24 hours, then mix them with 50% dimethazone or 0.5% carbendazim, which can not only make the seeds absorb water, but also play a bactericidal effect and reduce the occurrence of diseases during the growth period.

4. Raise seedlings in a narrow bed and sow seeds at the right time: first, the nursery ground is opened into a ditch and waist ditch with a depth of 60 cm and a width of 40 cm at the bottom of the ditch; then a seedbed with a width of 80 cm is made, and a drainage ditch with a depth of 30 cm and a width of 25 cm between the two adjacent seedbeds is communicated with the waist groove and the perimeter groove, and the bed surface is shaped into a tortoise back to facilitate drainage. It is better to sow in late March and early April, and it is easy to be harmed by late frost too early; too late, due to high temperature, short early growth period, poor seedling growth, easy to be damaged by diseases, pests and weeds, and low planting yield. The use of narrow bed seedling raising and short-term sowing can reduce the occurrence and spread of bacterial blight and other diseases and reduce the number of bacteria-carrying planting.