Occurrence of common diseases in Pseudostellaria heterophylla and effective control methods
Pseudostellaria heterophyllaViolet root rot is one of the common diseases of Pseudostellaria heterophylla, also known as moldy root, mud dragon, rotten cattail head, etc. The pathogen invades through the young root system of Pseudostellaria heterophylla, then spreads to the thicker branch roots and the main root. The diseased roots are initially yellowish-brown, later turning dark brown; in severe cases the cortex rots and turns black. On the surface of the damaged roots, purple-brown filamentous hyphae can be seen, and the hyphae tangle into root-like rhizomorphs. The rhizomorphs crisscross in a net-like pattern, and the hyphae within the strands connect in an H shape. The roots become covered with fungal strands, and in the later stage a layer of purplish-red velvety fungal film forms at the base of the rhizome and on the nearby soil surface. When the rhizome is infected, leaf growth is slow and the leaves are small, the leaf color turns yellow, the lower leaves drop early, the leaf tips or small branches die first, and finally the whole plant dies.
Occurrence pattern
The pathogen overwinters or oversummers as fungal strands and sclerotia in diseased roots and soil. It is mainly spread by contact with diseased roots, water flow, and farm tools, and is rarely spread by basidiospore dispersal. Diseased seedlings are the main route of long-distance spread. The pathogen is mostly distributed within 5—25cm of soil. It is an aerobic fungus. The temperature range for growth is 8—35°C, with an optimum of 27°C. When the disease occurs in a Pseudostellaria heterophylla field, central diseased plants appear first and then spread outward. If the water source is contaminated by the pathogen, the entire patch can become diseased. Soil with standing water, or acidic and gravelly soil, is prone to the disease. Continuous cropping land or land previously used for rice paddies, potatoes, and other susceptible crops has severe disease. This fungus can infect 113 species of plants in 48 families.
Control methods
Adopt comprehensive control measures such as strengthening cultivation management, improving environmental conditions, ensuring healthy growth of Pseudostellaria heterophylla, reducing the amount of pathogen, and applying pesticides at the right time, so as to keep the disease under control. Promptly remove weeds and tree roots around Pseudostellaria heterophylla to reduce sources of the pathogen. Scrape off the rotted and discolored tissue of diseased plants, cut off and destroy the decayed roots.
Cultivation management
For soil contaminated around areas where violet root rot has occurred, on the one hand thoroughly remove diseased residues such as residual roots, rotten roots, and rotten bark from the soil, and on the other hand turn and dry the soil. If conditions permit, it is best to replace the soil; apply more organic fertilizer to ensure vigorous growth of Pseudostellaria heterophylla and improve disease resistance; mix in sand to improve clay soil, dig ditches for drainage, improve the soil's aeration and drainage capacity, and destroy the environment suitable for the pathogen; where too thick a covering of soil affects root respiration of Pseudostellaria heterophylla, appropriately remove the surface soil; strengthen the control of other pests and diseases, increase ventilation and light penetration, increase the diversity of Pseudostellaria heterophylla, and establish a relatively balanced ecosystem, thereby improving disease resistance.
Chemical control
Chemical prevention must be early, at intervals of 6-7 days, for 3-4 consecutive applications, with a control effect of more than 60%. Pour 70% sodium pentachlorophenate wettable powder at 250-300 times dilution into the root soil, with a control effect of 60%; alternatively, scatter poisoned soil around diseased plants, that is, 40% quintozene 8-9 grams per square meter, mixed with 12.5-15 kilograms of fine soil and applied to the root area of diseased plants, with a control effect of 68%; or directly scatter 70% thiophanate-methyl wettable powder technical material around diseased Pseudostellaria heterophylla plants at 8 grams per plant, with a control effect of 62%. Control severe disease areas and suppress the occurrence of the disease.
For severely diseased plants (generally referring to plants with more than 1/2 dead), promptly dig them out and burn them in a centralized manner. Disinfect the surrounding soil with 50% amobam aqueous solution at 100-150 times dilution, or 40% quintozene powder poisoned soil at 50-100 times dilution, or 70% thiophanate-methyl wettable powder at 800-1000 times dilution, or quicklime powder, with a control effect of 60%.