Diseases and insect pests of Codonopsis pilosula and its control

I. Diseases

(1) Root rot.

The pathogen is a semi-known fungus, divided into chronic and acute disease two types. Chronic type: onset in mid-to late May. At the beginning of the disease, dark purple spots appeared on the lower fibrous roots or lateral roots, and then turned black and rotted. After the disease spread to the taproot, it gradually rotted from bottom to top. The rest of the rotten parts are mostly "half ginseng", close to the rotten parts are black-brown, and the stems and leaves on the ground gradually turn yellow, so that they die. Acute type, mostly in the middle and late June began to attack, ginseng roots once infected, almost at the same time disease, water-stained, soft texture, vascular bundles become light brown, a few days later, the whole ginseng soft rot. A small amount of gray mold can be seen in the decomposed parts.

Prevention measures: crop rotation and avoid continuous cropping; Before sowing, carefully select seeds, eliminate diseases, disinfect seeds, and use healthy Dangshen plants without diseases and insect pests as transplanted seedlings; do well drainage and waterlogging prevention work in rainy seasons; set up frames in the field to avoid vines spreading densely on the ground, which is conducive to ventilation and light transmission on the ground; check frequently in peak season, and immediately irrigate diseased plants and surrounding plants with 500 times solution of 25% carbendazim or 1500 times solution of 50% thiophane methyl to control disease spread.

(2) Purple feather disease

Main symptoms: purple streak disease can occur in the whole growing season of Dangshen. At the beginning of the disease, purplish red (or reddish brown) silk thread entwined on the epidermis of Dangshen root, accompanied by flannelette hyphal membrane. With the development of the disease, the fungiform cords and hyphae spread gradually, wrapping part or even the whole root system, and extending from the epidermis to the root. After the root of Codonopsis pilosula was destroyed, the symptoms of disease began to appear in the middle of June. First, the growth of plants gradually stagnated, and then the leaves of the aboveground parts began to wither and die from bottom to top. August is the peak of the disease, and the disease can last until October. Serious disease plot, Dangshen ground part often showed flaky death, the disease center is very obvious, the diseased plant is easy to pull up. When Dangshen was dug in autumn, the surface of the root strip of Dangshen was partially or completely wrapped with flannelette "red rust", and the quality decreased obviously. In serious victims, the fleshy part is almost destroyed, and the whole root strip is dry or wet rotted, completely losing its use value. Pathogenesis rule: The fungus overwinters in the soil with mycelium, root-like fungus cord or sclerotia, and can survive for many years in the soil. The disease spread mainly through soil, seedlings and undecomposed fertilizer, and the disease was most serious in continuous cropping land, followed by cultivated land, and the disease was lightest in newly reclaimed land. In addition, the disease is more serious in years with heavy rainfall and high humidity, and lighter in years with heavy rainfall and high humidity. On the contrary, the disease is lighter: the disease is heavier after planting in seedlings cultivated in continuous cropping land or rehmannia, and the disease is lighter after planting in seedlings cultivated in uncultivated land. Control measures: ① insist on rotation. The interval between the first crop and the next crop should be more than 3~4 years when codonopsitis was planted again in the cultivated land where codonopsitis had been planted. ② Select seeds and seedlings from disease-free fields. It is best to collect seeds on biennial, healthy and disease-free Codonopsis pilosula plants planted in uncultivated land, and select newly reclaimed uncultivated land or prepared seedlings planted with gramineous crops for many years. Nursery land is generally only applied chemical fertilizer, not farm manure, to prevent purple feather disease bacteria into nursery land. 3. Do a good job in seed and seedling disinfection. Before sowing or transplanting, seed soaking and root spraying with carbendazim, thiophanate-methyl or other fungicides can reduce the damage of purple feather to some extent.④ Deep ploughing before winter, soil treatment before planting. Before winter, the plot prepared for planting Codonopsis pilosula in the next year will be deeply ploughed, and some pathogens will be eliminated alternately by freezing and thawing in winter. The occurrence and spread of purple streak disease can be reduced by combining soil preparation and fertilization before transplanting, spraying 100 kg quicklime per mu to change the physical and chemical properties of soil, or spraying pentachloronitrobenzene mixed with fine soil to disinfect the soil. II. Pests Dangshen harm underground pests are mainly grub, ground tiger, mole cricket; ground pests have red spider. Control methods: ①, underground pest control methods: poison soil and poison bait trap. Poison soil preparation: 0.5 - 1.5 kg of 35% endosulfan and 15 kg of soil are used per mu, mixed and scattered in the roots of seedlings; poison bait preparation: 1 kg of fried cake powder is used per mu, 35 g of trichlorfon is added, mixed with water, and scattered on the edge of the ridge, furrow or ridge platform. 2, ground pest control methods: Dangshen ground pests are red spiders, generally occur in July, can be used 40% dimethoate emulsion 1000 - 1500 times liquid spray kill.

grubs