Control Methods for Common Pests and Diseases of Panax notoginseng

Panax notoginseng belongs to the genus Panax in the family Araliaceae. It is a perennial herbaceous plant and ranks second only to ginseng in the production of Chinese medicinal materials. Common pests and diseases include damping-off, anthracnose, root rot, phytophthora blight, aphids, red spider mites, and scale insects.

1. Damping-off: It occurs mostly in the high-humidity, low-temperature seasons of April to May, damaging the base of seedlings. In severe cases, seedlings die in patches. Infected seeds and seed buds turn blackish-brown and rot. After seedlings are affected, water-soaked yellowish-brown streaks appear at the base of the pseudostem (leaf petiole). As the disease progresses, these turn dark brown, and the diseased area then constricts, causing the seedlings to collapse and die. Control method: Drench the roots or spray with a 500-800 times dilution of 70% Dexon wettable powder.

2. Anthracnose: It damages leaves, petioles, stems, flowers, and fruits. When seedlings are affected, spindle-shaped reddish-brown spots or elongated, sunken, constricted bands encircling the base of the pseudostem (leaf petiole) appear, causing the seedlings to break and fall over. If necrotic spots occur at the top, the seedling tip dies back. Leaf lesions are grayish-green with concentric rings, later turning brown, with pink or black spore masses forming on the surface, and in the later stage rupturing and perforating. When stems and petioles are affected, spindle-shaped yellowish-brown canker spots form, causing the petioles to curl and the stems to twist and break, resulting in dried flowers and seeds. Lesions at the stem base not only cause mature plants to lodge but also induce rot of the "sheep intestine head" (rhizome bud). Affected fruits develop circular or irregular pale yellow sunken spots, and the fruit rind rots. Control method: Use fungicides such as a 800-1000 times dilution of 50% carbendazim wettable powder or a 1000 times dilution of 75% thiophanate-methyl wettable powder.

3. Root rot: It occurs mostly during the rainy seasons of June, July, and August. The longer the planting period, the more severe the disease. Diseased plants often first rot from the lateral roots, spreading to the main root, or yellowish-brown lesions appear at the rhizome head and stem base, continuously expanding and spreading, causing the entire root to rot. The leaves of diseased plants become abnormal in color, followed by wilting of the aboveground parts, drooping, and eventually the death of the whole plant. Control method: Drench the roots with a 300-500 times dilution of 58% Ridomil wettable powder or 50% carbendazim wettable powder.

4. Phytophthora blight: Panax notoginseng phytophthora blight often occurs in rainy seasons. It is prone to causing damage when the shade shed in the Panax notoginseng garden is too dense and humidity is too high, and the disease is mild after dry, rain-sparse weather turns cool. In the early stage of the disease, dark green irregular lesions appear on leaves or petioles, resembling scalding by boiling water, then turning brown, soft-rotting, wilting and drooping, and even adhering to the stems. When the rhizome is affected, yellowish-brown rot occurs. Control methods include strengthening field management, reducing temperature and humidity; promptly removing residues and burning them in a centralized manner; and spraying with a 500 times dilution of 65% zineb wettable powder.

5. Aphids: They damage stems and leaves, causing leaves to curl and plants to become stunted, affecting growth. Control method: Spray the leaf surface with a 1500 times dilution of Mospilan or a 2000 times dilution of 50% pirimicarb.

6. Red spider mites: They gather on the undersides of leaves to suck sap, causing them to turn yellow, wither, and fall off. Damage is severe from June to October. After the flower discs and fruits are affected, they become shrunken and shriveled. Control methods: 1) Clean the Panax notoginseng garden; 2) After late March, spray 0.2-0.3 degree Baume lime-sulfur mixture, once every 7 days, for 2-3 consecutive sprays; 3) During the peak disease period from June to July, spray a 2000-4000 times dilution of 5% hexythiazox.

7. Scale insects: They generally begin to occur in June each year, climbing up from the ground onto stems to cause damage after heavy rain; after July they damage flower axes and small petioles; damage is severe from August to October. The insect bodies attach to stems, flower axes, and pedicels to suck sap. After being affected, plants grow poorly, and florets become yellow and withered. In severe cases, dried flowers and small fruits dry up and fall off. Control methods: 1) During the pest outbreak period, strengthen inspection, and when insect bodies are found on plants, promptly crush them to death by hand; 2) After scale insects occur in the Panax notoginseng garden, spray a 1000-2000 times dilution of 40% methidathion or a 1000-2000 times dilution of 25% buprofezin during the nymph stage.