Chemical pesticides used to control plant diseases are collectively called fungicides. Fungicides include fungicides, bactericides, viricides, nematocides, protozoan killers, algaecides and herbicides used to control high parasitic seed plants, depending on the types of pathogens affected.
With the continuous improvement of people's living standards, more and more attention has been paid to the food safety, ecological safety and environmental safety after the use of pesticides, and the problems that need to be paid attention to when using pesticides are becoming more and more complex. However, we must follow the principle that while controlling plant diseases below the economic threshold, we should minimize the release of pesticides in nature. Therefore, we should first consider the disease cycle characteristics that need to be prevented and treated, and then determine strategies to achieve effective, economic and safe purposes. Principles for determining drug use: 1. Choose the safest, most economical and most effective agent according to the type of pathogenic bacteria; 2. Use a lower dosage; 3. Minimum times of application; 4. Use the simplest method of application.
There are many ways of using fungicides, the most important are spray and dusting, seed treatment and soil treatment.
1. Spray and dusting.
Foliar spray and dusting are the most important and effective methods to control airborne diseases during crop growth. Spray is easier to form an effective protective residual layer than the powder on the plant surface. Therefore, the disease prevention effect is better. Spray and dusting are not good adhesiveness when it rains. Surfactant added to reduce the surface tension can be well developed in spray, and the addition of compounds with better adhesion can enhance the adhesion of Fungicides on plant surfaces.
The most commonly used method is to spray the plant stems and leaves, dilute various fungicides that can be evenly dispersed in water, and spray them with spray apparatus. Traditional fungicides sprayed on the plant surface are easily affected by environmental factors, such as light, temperature, rain erosion, etc. The duration of efficacy is short, generally about a week. The fungicides with internal absorption can not be affected by external environmental factors and have a relatively long duration. The spraying technology for plant disease control is much higher than that for pest control. In order to play a good control effect, the applicator should not only understand the characteristics of the fungicides used, but also understand the biological characteristics of plant diseases, targeted spraying. For non-endogenous fungicides, it is necessary not only to spray on the stems and leaves that need to be protected, but also to form a uniform film on the surface of the stems and leaves. For the diseases on the back of the leaves, it is also necessary to spray the liquid on the back of the leaves. Although endophytic fungicides have the characteristics of distribution in plants, the common endophytic fungicides are mainly transported in the extraplasmic system. Only the liquid sprayed on the tender stems and leaves can be absorbed and transported to the upper functional leaves with water and inorganic salt. In addition to spraying uniform fungicides on the leaves, attention should be paid to making the liquid deposit on the stems and leaves of plants as much as possible.
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Two. Seed treatment
Many plant diseases are carried by seeds. Seed treatment aims at killing pathogens transmitted by seeds with chemicals, protecting or treating infected seeds so that they can germinate normally, and also can be used to prevent the infection of soil-borne pathogens. Treating seeds with protective fungicides can not only eliminate the bacteria adhering to the surface of seeds, but also protect seedlings from soil-borne pathogens. Treating seeds with endogenous fungicides can not only eliminate the bacteria latent in seeds, but also treat infected seeds.
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Systemic diseases, such as smut, stripe disease, rice seedling disease and dry-tip nematode disease of cereal crops, which are infected only by seed-borne fungi, are the most effective methods. Once the disease occurs in the field, it is impossible to control them with chemicals. Because of its small size and concentration, it is easy to carry out chemical treatment under artificial control conditions, and it can eliminate pathogenic bacteria more thoroughly, so seed treatment is the most economical and effective method in plant disease control.
Seed treatment methods: 1. soaking seeds 2. mixing seeds 3. seed coating method
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Three. Soil treatment
Soil is the habitat of many pathogenic bacteria and the source of the first infection of many plant diseases. Soil treatment is the most effective way to control soil-borne diseases. In order to ensure the safety of crops, soil fumigation treatment requires a certain waiting period, that is, the interval between soil medication and planting crops. The interval depends on the medicament, soil type, soil temperature, the sensitivity of seedlings to medicament and climatic conditions. Generally, the interval should be 2-4 weeks.
The commonly used soil treatment methods are as follows: 1. Irrigation 2. Ditch application 3. Spreading (mixing) 4. Injection method.
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