Key Techniques for the Prevention and Control of Pests and Diseases in the Medicinal Herb Polygonatum (Huangjing)

Diseases

Black spot disease is the main disease of Polygonatum. The pathogen is a type of imperfect fungus (Deuteromycete). It damages the leaves. In the early stage of the disease, irregular yellowish-brown spots appear from the leaf tip, with a purplish-red margin at the boundary between diseased and healthy tissue; afterward the spots spread downward, and in the rainy season it becomes more severe. The diseased parts of the leaves turn yellow and withered. Control methods: Clean the garden at harvest time to eliminate diseased plant debris; before the disease occurs and in the early stage, spray 1:1:100 Bordeaux mixture or 50% Tuzet 1000x solution, once every 7-10 days, for several consecutive applications.

Leaf spot disease. Symptoms: It mainly damages the leaves. In the early stage of the disease, it starts from the base, and faded spots appear on the leaf surface; afterward the spots enlarge into an elliptical or irregular shape, about 1cm2 in size, pale white in the center, brown at the margins, with an obvious yellow halo near the healthy tissue, and the spots resemble an eye shape. When the disease is severe, multiple spots merge and cause the leaves to wither and die, and it can gradually spread upward until finally the leaves of the whole plant wither, die and fall off. The pathogen of this disease belongs to the subphylum Deuteromycotina. Disease characteristics: This disease generally appears as new spots in early June on the leaves of plants that did not die in winter, then in early July it transfers to the base leaves of newly sprouted plants of the current year and begins to develop, gradually moving upward; by the end of July the disease is already quite severe, with whole plants withering and dying. In August and September, along with plant death in the field caused by various other reasons, the disease reaches its peak. In October, scattered spots appear again on diseased plants, and in early November it occurs commonly and severely. Control is the same as the control methods for black spot disease.

Anthracnose. Symptoms: It mainly damages the leaves, and the fruit can also be infected. After infection, spots first appear at the leaf tip and leaf margins. Initially they are small reddish-brown spots, then expand into elliptical or semicircular dark brown spots; the center of the spot is slightly sunken and often perforates and falls off, the margin is slightly raised and reddish-brown, with a yellow halo on the outside; under humid conditions, small black dots are scattered on the spots. The pathogen is a fungus of the subphylum Deuteromycotina, class Coelomycetes, order Melanconiales, genus Colletotrichum. Occurrence characteristics: It begins in late April and is most severe from August to September. There is a trend of worsening year by year. Control methods: Carbendazim or the same control methods as for black spot disease.

Root rot. Symptoms: This disease mainly infects the roots. It belongs to the genus Fusarium, an imperfect fungus. In the early stage of the disease, water-soaked brown necrotic spots appear on the roots; when severe, the interior of the entire root rots, leaving only fibrous vascular bundles, and the diseased part is brown or reddish-brown. When humidity is high, a white mold layer (that is, conidia) appears on the surface of the rhizome. Because the roots rot, diseased plants are easily pulled up from the soil. As the disease develops in affected plants, aboveground growth is poor, and the leaves gradually turn yellow from the outside inward, until finally the whole plant withers and dies. Control methods: Copper preparations or metalaxyl-hymexazol, carbendazim, etc. can be used for soil disinfection.

Stem rot. Symptoms: In affected plants, it gradually spreads upward from the lower leaves. It belongs to the genus Fusarium, an imperfect fungus, and shows symptoms of green wilt (that is, a bluish-gray color, as if scalded by boiling water); finally the whole plant shows symptoms and is easily distinguished from healthy plants. Some diseased plants show acute symptoms without an obvious process of gradual development from bottom to top; this situation is more commonly seen after rain followed by sudden clearing. From the first appearance of diseased leaves to symptoms on the whole plant generally takes about one week, in short cases only 1-3 days, and in long cases it can last more than 15 days. The stem base of diseased plants becomes soft, and the interior is hollow and loose (which can be identified by squeezing with the hand). They easily break and fall in the wind. The root system of the plants is obviously poorly developed, with few and short roots that turn black and rot. When the stem is cut open for examination, the pith is hollow and loose, and red symptoms can be seen in the roots, stem base and pith. Control methods: Same as for root rot.

Pests

White grubs: They belong to the order Coleoptera, family Scarabaeidae. The larvae cause damage by biting off seedlings or gnawing on seedling roots, causing broken seedlings or cavities in the roots, and the damage is severe. For medication, use the same as for cutworms, or kill them with conventional low-toxicity pesticides.

Cutworms: They damage seedlings and rhizomes. Control methods: 75% phoxim emulsifiable concentrate can be used to dress seeds at 0.1% of the seed amount; during the field occurrence period, irrigate with 90% trichlorfon 1000x solution; use black light lamps or poison bait to trap and kill adults; apply manure only after it is fully decomposed, preferably using high-temperature composting.