Ginseng Disease Prevention and Control Methods and Key Technical Points
Ginseng is a plant of the genus Panax in the family Araliaceae, mainly produced in China's Jilin, Liaoning, Heilongjiang and other provinces. Its roots, stems, leaves and fruits are used as medicine, and it has the functions of greatly tonifying vital energy, strengthening the heart and rescuing from collapse, benefiting the heart and restoring the pulse, promoting fluid production and calming the mind. There are many types of ginseng diseases, more than 20 in China, and those that currently occur commonly and cause serious damage in production include...
Ginseng is a plant of the genus Panax in the family Araliaceae, mainly produced in China's Jilin, Liaoning, Heilongjiang and other provinces. Its roots, stems, leaves and fruits are used as medicine, and it has the functions of greatly tonifying vital energy, strengthening the heart and rescuing from collapse, benefiting the heart and restoring the pulse, promoting fluid production and calming the mind. There are many types of ginseng diseases, more than 20 in China, and those that currently occur commonly and cause serious damage in production include ginseng black spot, Phytophthora blight, sclerotinia rot and rust rot.
I. Ginseng black spot Symptom identification It mainly damages leaves, and can also damage stems, pedicels, fruits, seeds and other parts. Leaf lesions are nearly circular or irregular, yellow-brown, slightly zonate, with a pale yellow halo outside and a black mold layer on top. The lesions mostly cause leaves to wither and fall early. Stem lesions are oval, yellow-brown, expanding upward and downward, with the center sunken and blackened, bearing a black mold layer, causing the stems to lodge. Affected fruits produce brown spots on the surface, become shriveled and drop early. The black mold layer produced on the lesions is the pathogen's conidia. This disease occurs commonly and is one of the most serious diseases of ginseng.
Pathogen and disease occurrence pattern Ginseng black spot is caused by fungi of the genus Alternaria in the subphylum Deuteromycotina. Conidiophores are born in bundles of 2-16, brown, with lighter tips; conidia are borne singly or in chains of 2-3, obclavate, yellow-brown, with a short beak. The pathogen overwinters as mycelium and conidia on diseased residues, in soil and on the seed surface, becoming the primary infection source for the disease the following year. Conidia spread by wind and rain, and germ tubes penetrate directly through host stomata or epidermis. When environmental conditions are suitable, large numbers of conidia are produced on the lesions, and after spread they cause multiple secondary infections. The optimum temperature for conidial germination is 15°C-25°C, with relative humidity above 98%. In Northeast China, the disease begins in mid-May, and July-August is the peak period. High humidity and frequent rain are key factors for disease epidemics.
Prevention and control measures
① Select and keep disease-free seeds, and carry out seed disinfection. Soak with polyoxin at 200 mg/kg or 50% mancozeb 1000-fold solution for 24 hours, or treat seeds at 0.2%-0.5% of seed weight.
② Remove diseased residues. In early spring, use 100 mg/kg polyoxin or 1% copper sulfate for comprehensive disinfection of ginseng bed paths and ginseng sheds.
③ Choose plots with high terrain and good drainage and aeration for planting ginseng. The bed surface of double-transparent sheds must be covered with fallen leaves, and reasonable light exposure should be achieved. During the hot, rainy, high-temperature season in the dog days, measures should be taken to prevent rain and avoid strong light.
④ Begin spraying for control at the early leaf-unfolding stage of ginseng seedlings. Use 50% mancozeb 800-fold solution, 80% Daconil 600-fold solution, polyoxin 100-200 mg/kg, imazalil 400-fold solution, 1:1:120 Bordeaux mixture, etc. for spraying, once every 7-10 days, spraying 3-5 times depending on disease progression.
II. Ginseng Phytophthora blight symptom identification
It damages stems, leaves and roots. Leaf lesions are water-soaked, irregular, dark green, with no obvious margin; the lesions expand rapidly and rot, and the entire compound leaf wilts and droops. Dark elongated spots appear on stems, which rot quickly, causing the stems to soften and lodge. The roots show water-soaked yellow-brown soft rot, the internal tissue has a yellow-brown pattern, the root bark is easily peeled off, entangled with clumps of soil adhered to by white mycelium, and it has a special fishy odor.
Pathogen and disease occurrence pattern
Ginseng Phytophthora blight is caused by fungi of the genus Phytophthora in the subphylum Mastigomycotina. Mycelium is cottony, colorless, non-septate and branched. Sporangia are oval, zoospores are round, and oospores are spherical and yellow-brown. The pathogen overwinters as mycelium and oospores in diseased residues and soil. When conditions are suitable the following year, it directly infects ginseng roots with mycelium, or forms large numbers of sporangia that spread to aboveground parts and infect stems and leaves to cause disease. Wind, rain and agricultural operations are the main ways the disease spreads. During the ginseng growth period, multiple secondary infections can occur. In Northeast China, the disease begins in June, and mid-July to mid-August is the peak period. When the temperature is above 20°C and soil moisture is above 50%, Phytophthora blight will break out severely. Poor ventilation and light transmission in ginseng beds, soil compaction, excessive nitrogen fertilizer and excessive density all favor the occurrence and epidemic of Phytophthora blight.
Prevention and control measures
① Strictly prevent rain leakage in ginseng sheds, and pay attention to drainage, ventilation and light transmission. For ginseng cultivation in double-transparent sheds, the bed surface must be covered with fallen leaves; for ginseng cultivation under forest, broad-leaved forests with larger tree crowns must be selected.
② Strengthen field management, maintain appropriate density, remove weeds in time, and pay attention to loosening soil to reduce humidity.
③ Timely discover and eliminate diseased plants. Pulled-out diseased plants must be moved outside the bed and burned, and the diseased holes should be sealed and sterilized with quicklime or 1% copper sulfate solution. Thoroughly remove diseased residues in autumn.
④ Chemical control: before the rainy season begins, spray 1:1:160 Bordeaux mixture, 40% amobam 1000-fold solution, 40% fosetyl-aluminum 300-fold solution, 25% metalaxyl 600-fold solution, 72.2% Previcur 600-fold solution once every 7-10 days, and spray 3-5 times consecutively depending on disease severity.