Wood fungicide at high temperature maintenance measures
In agricultural production, the insecticides used to prevent and control crop diseases caused by microbial infection are fungicides. In other words, before, during or after the growth of crops and other stages, according to the law of disease occurrence, in conjunction with other control measures in the comprehensive control program, the use of chemical agents to treat crops and their growing environment, in order to reduce or eliminate disease agents or change the metabolic process of crops to improve crop resistance, to prevent or prevent the occurrence and development of diseases. To "drive down" diseases to economically, ecologically and socially "bearable" conditions, and to ensure a good crop harvest.
As early as in the 18th century, human beings were using sulfur, copper sulfate and other inorganic chemicals to control crop diseases. In 1851, the French discovered the insecticidal and bactericidal effect of stone sulfur mixture. In 1882, Frenchman A. In Bordeaux, Mialdey discovered that lime and copper sulfate in a certain proportion of the medicine solution against grape downy mildew and other crop diseases is significantly more effective than copper sulfate, since then this formula gradually became popular around the world, this is now many Chinese farmers have been using Bordeaux solution. In 1914, Germans first used phenylmercuric acetate (Celisan) and ethylmercuric chloride (celisan) to treat wheat seeds to prevent smut, opening up the history of organic mercury fungicide; In 1934, Tisdale (W.H.) and Williams (I.) and Martin (H.) simultaneously reported the control effect of thiram, a compound of dithiocarbate, on plant diseases. It marks a new era of using synthetic organic fungicides to control plant diseases, which is also the first major breakthrough in the history of chemical control of plant diseases in the 20th century. In the 1960s, rice blast Jing, ruxin, benzoin and other endogenic fungicides have appeared and made further development of fungicides.
The use of fungicides in a variety of ways, the most widely used is spray, followed by soil treatment, in recent years the development of strong is seed treatment, in addition to smear, dipping flower, injection, spray, irrigation and so on. The determination of the use of a fungicide is not only based on the occurrence law of the disease, but also based on the characteristics of the fungicide, especially the mode of action and conduction mechanism, which need to be determined after our comprehensive analysis.
The action mode of fungicides can be divided into protective, therapeutic, eradication, etc. Related concepts will be introduced in the table.
The conduction characteristics of fungicide can be divided into
1, no internal absorption conduction effect, the drug liquid falls on the plant leaves, fruit surface to form a drug film, prevent the invasion of pathogens. Such as most sulfur preparations, copper preparations, etc.;
2, local internal absorption with transpiration flow or short distance movement between cells, such as frosting urea cyanide;
3, semi-inward absorption or cross-layer transfer, such as ether and pyrimethil ester, etc., move in the leaf;
4. Upward transport and inward aspiration, which are absorbed by plant roots and transmitted upward with the flow direction of the transpiration liquid, resulting in the accumulation of the drug liquid in high transpiration sites such as leaf tip and leaf margin; But less transpiration, such as fruit and young leaves, is scarce; If applied at the base of the leaf, the agent moves toward the tip and accumulates, but rarely in the opposite direction. Most endofungicides belong to this conduction characteristic. Such as carbendazim, triazolone;
5, true inward absorption, by plant roots, stems, leaves after absorption of two-way conduction upward and downward. Examples include metalaxyl and aluminium triethylphosphonate.
Fungicide according to the object of action is divided into fungicide, bactericide, viricide and so on. But some fungicides are often effective against fungi, bacteria, viruses, and others are only effective against a certain class of pathogens.
To now used for crop fungicides to remove Bordeaux liquid, sulfur powder, stone sulfur mixture and other inorganic fungicides in addition, there are many categories of organic synthetic fungicides, such as mancozeb, corbicide and other organic sulfur fungicides, carbendazol, benzomycin and other carbamate, ethyl phosphorus aluminum, methyl trichophosphorus and other organophosphorus, fluosilazole, phenyloxyconazole, propionazole and other azole.
