Key Technical Points for Weed Control in the Cultivation of Chinese Medicinal Herbs

Weed control in the cultivation of Chinese medicinal herbs generally employs chemical control methods.

I. Precautions

1. Pay attention to the selectivity, specificity and timing of chemical herbicides, and do not misuse or use them indiscriminately.

2. Strictly adhere to the restricted dosage. The use of herbicides should be based on the specific soil type, take into account the field microclimate, and strictly follow the dosage range, concentration and application rate specified in the product instructions.

3. Mix pesticides rationally. When two or more herbicides are mixed for use, the mixing ratio, application time and spraying technique must be strictly controlled, and whether they have antagonistic effects or other side effects on each other must be considered. A small amount can first be taken for a miscibility test; if precipitation, flocculation, layering, floating or deterioration occurs, it indicates that their safety has changed and they must not be mixed. In addition, attention should be paid to the synergistic function of the mixture. For example, the herbicidal effect of a mixture of benthiocarb and propanil is greater than the sum of the herbicidal effects of the individual agents, so the dosage of the mixture should be reduced when used (generally within half the dosage of each individual agent) to avoid phytotoxicity and ensure the safety of the medicinal materials.

4. Pay attention to application isolation and wind direction, and keep the droplets from being too fine, so as to avoid drift causing phytotoxicity to adjacent farmland, and also pay attention to the impact on the following crop.

5. Master the optimal timing and technical essentials for applying herbicides, properly store the chemicals to prevent misuse, and thoroughly clean the spraying equipment to avoid misuse that causes phytotoxicity to other crops.

6. Pay attention to the influence of environmental conditions on herbicides. Factors such as temperature, moisture, light, soil type, organic matter content, and the level of soil tillage and land preparation will all directly or indirectly affect the herbicidal effect of herbicides.

7. Apply chemicals flexibly. For weed control by the soil-application method at the base of medicinal plants, it should be carried out under conditions without dew, so as to prevent the stems and leaves from being harmed by contact with the chemical solution. For chemicals to which crop seedlings and embryos are sensitive, soil treatment should be applied after sowing and covering the seeds, and the sowing quality should be improved as much as possible and the seeding rate appropriately increased. For some transplanted medicinal materials, because their seedlings are large while the weeds are small, concentrated application can be adopted in the seedling band (20—30 cm wide near the seedlings). For herbicides with poor selectivity or contact-killing action, protective application should be implemented, that is, the chemical solution is sprayed directly or splashed onto the soil surface, trying not to contact the medicinal seedlings, and application must not be delayed until the seedlings are vigorous and the green leaf area is large. If the crop rotation permits, measures such as dryland irrigation, wetting of paddy fields and film mulching to induce germination can be taken before sowing or transplanting the medicinal materials, so that the weeds sprout in advance and are then killed with chemicals.

8. At present, there are no herbicides on the market specifically for medicinal materials; most are borrowed herbicides for vegetables, fruit trees and the like. Therefore, herbicides must be purchased or weed control operations carried out under the guidance of experts or technicians with practical experience, so as to avoid economic losses and adverse consequences.

II. Applicable Pesticides

Common weeds in medicinal herb fields mainly include barnyardgrass, foxtail grass, lovegrass, crabgrass, goosegrass, shortawn foxtail, white cogongrass, redroot pigweed, purslane, small cockscomb, polygonum and goosefoot, Russian thistle, pepperwort, shepherd's purse, alligator weed, lambsquarters, field bindweed, and so on. These weeds not only compete with the medicinal plants for nutrients and water in the soil, but also degrade the environment and spread diseases and insect pests, seriously affecting the yield and quality of Chinese medicinal herbs. In the process of weed control, different methods should be adopted for different weeds according to their different characteristics. Selecting chemical agents for weed control not only saves money and labor, but is also relatively thorough and can achieve better control results.