What are the control methods for schisandra phytotoxicity?

In recent years, phytotoxicity from pesticides has frequently occurred in the large numbers of schisandra plants cultivated across various regions. In mild cases it reduces yield, and in severe cases it causes total crop failure and no harvest for the entire orchard, so sufficient attention should be paid to it.

The common acute phytotoxicity in schisandra is mainly caused by improper pesticide application and pesticide drift. Phytotoxicity in schisandra caused by pesticide drift is mainly the result of using the 2,4-D butyl ester herbicide in corn fields and wheat fields. Wu Zhongsheng of Xiagou Village, Wangshi Town, Haicheng City, planted 100 mu of schisandra and once suffered phytotoxicity from 2,4-D butyl ester drift, resulting in total crop failure and no harvest for the entire orchard that year. Schisandra is highly sensitive to the herbicide 2,4-D butyl ester. Acute phytotoxicity occurs quickly, and once it occurs it causes wilting, leaf curling, flower drop, fruit drop, loss of green color, slow growth, delayed growth period, and death of severely affected plants, causing huge losses to farmers' cultivation. The following measures can be taken to control this type of phytotoxicity.

I. Scientifically select sites and pesticides to avoid herbicide phytotoxicity

Introduce and screen other safe and efficient herbicides to replace 2,4-D butyl ester. Actively adopt safe herbicides that can achieve the ideal weeding effect without easily causing phytotoxicity. Options include the currently promoted Hanfengbao and others. At the same time, set up a 200 m isolation belt around the schisandra base. It is worth noting that some farmers are rather careless in the use of spray equipment and do not clean it thoroughly. If a sprayer that has been used for 2,4-D butyl ester is not thoroughly cleaned and is then continually used to spray fungicides, it often causes "secondary phytotoxicity" in schisandra. Some farmers also do not put a protective hood on the sprayer nozzle when spraying 2,4-D butyl ester, the nozzle position is too high above the ground, and the liquid pump pressure is too great, so droplet volatilization or drift causes phytotoxicity. Surveys show that 50% of schisandra seedling deaths in production are caused by herbicide phytotoxicity, and this must be taken seriously.

II. Remedial measures for phytotoxicity

In general, after schisandra phytotoxicity appears, quick-acting fertilizers such as 1-2% urea and 0.3% potassium dihydrogen phosphate can be sprayed on the leaves to promote growth and improve resistance to pesticides; 20-40 ml of 0.1% brassinolide per mu can also be sprayed after mixing with 50 kg of water; in severe cases, an additional spray of 85% gibberellin crystalline powder at 20 mg/kg is needed for remediation. When using gibberellin, attention should be paid to its formulation. Water-soluble types can be directly diluted with water, and dissolving them with alcohol or white liquor is strictly prohibited; non-water-soluble types must first be dissolved with a small amount of alcohol or 60-degree white liquor and then diluted with water before use.

III. Chronic phytotoxicity

This is mainly phytotoxicity caused by the accumulation of pesticide residues in the soil or on plants due to multiple applications or repeated applications over successive years. The symptoms of chronic phytotoxicity are not obvious and can only be judged by comparison with normal plants, but ultimately they seriously affect yield and quality. Before schisandra cultivation or seedling raising, if the previous crop used herbicides, "Wotu'an" can be used to degrade residual pesticides in the soil. Method and dosage: use "Wotu'an" to treat the soil during the farmland fallow period. At this time, use 750 g per mu, add water at 2000 times, stir evenly until fully dissolved, spray evenly on the ground with sprinkler irrigation equipment, then plow and leave fallow so that pesticide residues can be fully degraded. Then, a few days before sowing or planting, use another 750 g of "Wotu'an" per mu, add water at 2000 times, fully dissolve, spray and water the seedling bed or the surface of the planting strip, and then sow or transplant. Note that "Wotu'an" should be prepared immediately before use and must not be mixed with acidic pesticides; it is not suitable for foliar spraying; it should be stored sealed and protected from light.