A Detailed Guide to Identifying and Controlling Pests and Diseases of Codonopsis pilosula

I. Diseases

（1）Root Rot。

       The pathogen is a type of fungus imperfectus (Deuteromycete), and the disease occurs in two forms: chronic and acute.Chronic form:It begins to develop in mid to late May. In the early stage, dark purple lesions appear on the lower fibrous roots or lateral roots, which then turn black and rot. After the disease spreads to the main root, it gradually rots from the bottom upward. What remains unrotted is mostly a "half-length root," with the part near the rot appearing dark brown; the stems and leaves above ground gradually turn yellow and eventually die.Acute form, which mostly begins to develop in mid to late June. Once the root is infected, almost the entire root is affected at the same time, becoming water-soaked, soft in texture, with the vascular bundles turning light brown; within a few days the whole root becomes soft and rotted. On the rotted parts, a small amount of grayish-white mold-like growth can be seen. 

Control measures: Practice crop rotation and avoid continuous cropping; carefully select seeds before sowing, remove diseased seeds, disinfect the seeds, and use healthy, pest- and disease-free Codonopsis pilosula plants as transplanting seedlings; carry out drainage and waterlogging prevention during the rainy season; erect trellises in the field to avoid the vines lying densely on the ground, which helps ventilation and light penetration at ground level; during peak disease periods, inspect frequently, and upon finding diseased plants, immediately drench the diseased clump and surrounding plants with a 500-fold dilution of 25% carbendazim or a 1500-fold dilution of 50% thiophanate-methyl to control the spread of the disease. 

（2） Violet Root Rot  

        Main symptoms: Violet root rot can occur throughout the entire growing season of Codonopsis pilosula. At the initial stage, purple-red (or reddish-brown) thread-like mycelial strands can be seen entwining the epidermis of the Codonopsis pilosula root, accompanied by a felt-like mycelial membrane. As the disease progresses, the mycelial strands and hyphae gradually spread, enveloping part or even the entire root system, and extend from the epidermis into the interior of the root. After the Codonopsis pilosula root is damaged, symptoms generally begin to appear on the above-ground parts in mid-June: first the plant's growth gradually stalls, then the above-ground leaves begin to wither and die from the bottom upward. August is the peak period of disease occurrence, and the disease can continue until October. In severely affected plots, the above-ground parts of Codonopsis pilosula often die in patches, with a very obvious disease center, and diseased plants can be pulled up easily. When harvesting Codonopsis pilosula in autumn, part or all of the surface of the affected roots can be seen covered with felt-like "red rust," and quality is markedly reduced. In severely affected roots, the fleshy part is almost completely destroyed, and the entire root becomes dry-rotted or wet-rotted, completely losing its usable value.         Pattern of occurrence: The pathogen overwinters in the soil with diseased roots as mycelium, rhizomorphs, or sclerotia, and can survive in the soil for many years. The disease spreads mainly through soil, seedlings, and undecomposed fertilizer. It is most severe in continuously cropped land, next in cultivated land where crops have been grown, and least severe in newly reclaimed virgin land. In addition, disease is more severe in years with high rainfall and high humidity, and less severe otherwise; it is more severe in clayey, compacted soil, and less severe otherwise: seedlings raised in continuously cropped land or cultivated land are more severely affected after planting, while seedlings raised on virgin land are less severely affected after planting.         Control measures: ① Persist with crop rotation. When Codonopsis pilosula is planted again on land where it has already been grown, the interval between the previous crop and the following crop should be more than 3 to 4 years.  ② Select seeds and seedlings from disease-free fields for seed production. It is best to collect seeds from robust, disease-free two-year-old Codonopsis pilosula plants grown on virgin land, and to raise seedlings on newly reclaimed virgin land or on cultivated land where gramineous crops have been grown for many years. Seedling-raising land should generally be given only chemical fertilizer, not farmyard manure, to prevent introducing the violet root rot pathogen into the nursery land.  ③ Do a good job of disinfecting seeds and seedlings. Before sowing or transplanting Codonopsis pilosula seeds and seedlings, treat them by soaking the seeds or spraying the roots with carbendazim, thiophanate-methyl, or other fungicides for disinfection, which can reduce the damage from violet root rot to a certain extent. ④ Deep plow and freeze the soil before winter, and treat the soil before planting. Before winter, deep plow and freeze the plot planned for Codonopsis pilosula planting the following year, using the alternating freeze-thaw of winter to kill some of the pathogen. Before transplanting Codonopsis pilosula, when preparing the land and applying fertilizer, spread 100 kg of quicklime per mu to change the physical and chemical properties of the soil, or mix quintozene with fine soil and broadcast it to disinfect the soil; either method can reduce the occurrence and spread of violet root rot.             II. Insect Pests        The main underground pests harming Codonopsis pilosula arewhite grubs、cutworms、mole crickets;the above-ground pest isred spider mites。        Control methods: ① Control methods for underground pests: use poisonous soil and poisonous bait to trap and kill them. Preparation of poisonous soil: per mu, use 0.5-1.5 kg of 35% endosulfan and 15 kg of soil, mix them and spread the mixture among the seedling roots; preparation of poisonous bait: per mu, use 1 kg of roasted fragrant cake meal, add 35 g of trichlorfon, mix well with water, and spread it on the surface of the seedbed and beside it, in the furrows or on the ridges. ② Control methods for above-ground pests: the above-ground pest of Codonopsis pilosula is the red spider mite, which generally occurs in July and can be killed by spraying with a 1000-1500-fold dilution of 40% dimethoate emulsion.

 

white grubs