Detailed Explanation of Pollution-Free Control Techniques for Rice Pests and Diseases

I. Agricultural Control

Agricultural control is the foundation for achieving pollution-free control of rice pests and diseases, and its basic principle is to create an environment that favors crop growth and development while disfavoring the breeding of pests and diseases.

1. Increase the application of organic fertilizers and gradually reduce the amount of chemical fertilizers used. In production, relying solely on chemical fertilizers (especially nitrogenous chemical fertilizers) while neglecting the cultivation, composting and use of organic fertilizers is one of the important reasons for the current severe occurrence of rice pests and diseases. Therefore, it is necessary to change concepts, attach importance to developing animal husbandry, planting green manure crops and composting various types of farmyard manure, and establish a new fertilization model based primarily on organic fertilizers and supplemented by chemical fertilizers. In order to increase the sources of organic fertilizer, it is required to plow and sow green manure or other crops in winter to prevent fields from overwintering fallow. Doing so can not only reduce the overwintering base of the striped stem borer (Chilo suppressalis) and sheath blight sclerotia, but also improve the soil. Organic fertilizer is a complete fertilizer and can comprehensively supply the various nutrient elements needed by crops, but it is also a slow-release fertilizer, and most of the nutrient elements it contains cannot be directly utilized by plants; they must first be decomposed by microorganisms into ammonium nitrogen and inorganic salts before they can be absorbed. The early stage of rice growth is precisely the key period when quick-acting fertilizers (especially nitrogen fertilizer) are needed. If the required nutrients cannot be guaranteed, it will inevitably affect normal tillering, resulting in failure to grow vigorously in the early stage and then delayed maturity with excessive vegetative growth in the later stage. Therefore, when increasing the application of organic fertilizer, attention must be paid to resolving the above contradiction between supply and demand in order to achieve safe nitrogen uptake by rice (that is, continuously and evenly supplying nitrogen fertilizer according to the needs of each growth stage, neither too much nor too little, so that rice grows steadily in the early and middle stages and does not senesce prematurely or grow excessively in the later stage). For example: when green manure is the main fertilizer source, first, the total application amount must be controlled, with about 1000 kg of fresh grass applied per 667 sq m, and not too much; second, when sowing green manure, green manure varieties with different degrees of decomposition difficulty must be mixed and sown; third, plowing must be carried out early at the appropriate time to promote the decomposition of green manure. When barnyard manure and cake fertilizer are the main fertilizer sources, efforts should be made to fully decompose them before application, they should be distributed evenly during application, and attention should be paid to intermittent irrigation after transplanting to promote the decomposition of organic fertilizer. Increasing the application of organic fertilizer does not exclude the use of chemical fertilizers; the two should be combined. At the beginning of tillering, apply 50 kg to 100 kg of silicon-manganese compound fertilizer per 667 sq m in a timely topdressing to promote early and rapid growth and steady development of the seedlings, laying a good foundation for pollution-free rice production.

2. Select high-quality, high-yield, disease-resistant varieties to prevent rice blast damage. When selecting high-quality, high-yield varieties, they are required to also have resistance to rice blast. This is because chemical control of rice blast is relatively ineffective, while the control effect of selecting resistant varieties is good and not difficult to achieve. The specific method is to conduct one survey of the incidence of panicle neck blast on local main varieties and newly introduced varieties each year during the heading and grain-filling stage of rice. Any variety with an average incidence of panicle neck blast reaching 3% to 5% should no longer be planted the following year and must be resolutely eliminated. At the same time, continuously introduce high-quality, high-yield, rice blast-resistant varieties for trial planting and promotion, so that they gradually replace varieties that have lost resistance. As long as this work is done persistently, the occurrence and epidemic of rice blast can be avoided.

3. Advocate the application of silicon fertilizer to enhance the stress resistance of rice. Rice is a silicon-demanding crop, and the silicic acid content in rice plants is as high as 11.3%. Relying only on natural supply cannot meet the needs of normal growth, so it is necessary to advocate returning rice straw to the field and increasing the application of silicon fertilizer. After silicic acid accumulates on the surface of stems and leaves, it can make the stem and leaf surfaces siliceous, inhibiting the invasion and spread of pathogens such as rice blast and brown spot, and also making it harder for the striped stem borer to invade and feed, thereby reducing pest and disease damage. In addition, silicic acid can also promote the absorption and transport of nitrogen, phosphorus and potassium, promote oxygen transport within rice plants, enhance the oxidation capacity of the root system, ensure normal growth of rice, and significantly enhance lodging resistance.

4. Improve seedling-raising methods and attach importance to cultivating strong seedlings. From the perspective of pollution-free production, there are currently two aspects of rice seedling-raising methods that need improvement: first, the application of chemical nitrogen fertilizer in seedling fields causes seedlings to grow tender and green, making them prone to attracting pests and diseases and increasing mechanical damage during transplanting. The area of seedling fields is relatively small, so decomposed human and animal manure can be used as base fertilizer to meet the needs of normal growth during the seedling stage. Potassium sulfate or potassium chloride, etc. should be changed to topdressing. In this way, truly healthy seedlings can be cultivated, not merely good-looking ones. The second is the phenomenon of indiscriminate pesticide application in seedling fields. Seedling fields are bridge fields for various natural enemies of pests, such as parasitic wasps and rice field spiders, to transition to the main fields. Indiscriminate pesticide application will make it difficult for them to reproduce and difficult for them to play their role in controlling pests. Therefore, it is necessary to change the concept of treating small fields to protect large fields and adopt scientific pesticide application methods to achieve the goal of protecting beneficial organisms and controlling pests.

5. Implement scientific water management to reduce rice diseases. Water is the lifeblood of normal rice growth and development, and it is also one of the causes of disease induction. In scientific water management, it is necessary to adhere to the water management principles of shallow irrigation at the tillering stage, draining the field when enough tillers have been reached, implementing intermittent irrigation after rewatering, and keeping the field surface moist. In some places, due to difficulties in water sources or poor management, long-term deep irrigation is carried out, which easily leads to severe occurrence of small sclerotium disease, sheath blight and rice blast. This problem must be taken seriously and corrected.