Introduction to the varieties and action modes of common fungicides

Fungicides, also known as biocide, algicide, microbicide, etc., usually refer to chemical agents that can effectively control or kill microorganisms-bacteria, fungi and algae in the water system. Internationally, it is usually used as a general name for the control of all kinds of pathogenic microorganisms. So what are the common fungicides? What are the modes of action?

First, Dyson zinc

1. Mode of action: the original drug is grayish white or yellowish powder with rotten egg flavor. It is a protective fungicide, which has strong contact killing effect on many kinds of bacteria, such as downy mildew, late blight, anthracnose and so on.

Its effective components are easy to be oxidized to isothiocyanate in water, which has a strong inhibitory effect on the enzymes containing-SH group in the pathogen, and directly kills the spores of the pathogen, prevents the invasion of bacteria, and is safe for crops. We should master the use of drugs in the early stage of the disease, and the duration of the disease is relatively short. It is low toxic to higher animals and has irritating effect on skin and mucosa.

2. Control objects and techniques: at the initial stage of the disease, spraying with 500 times of 80% wettable powder can control melon sudden drop disease, standing blight, corner spot, Fusarium wilt, anthracnose, downy mildew and other diseases. Spray again every 7 to 10 days.

II. Mancozeb

1. Mode of action: mancozeb is a broad-spectrum protective fungicide, and its mechanism is to inhibit the oxidation of pyruvate in bacteria. The original medicine is grayish yellow powder, which is easy to decompose when it is wet at high temperature. It is low toxic to higher animals and has a certain irritating effect on human skin and mucous membrane. It was toxic to fish, and the phenomenon of "three causes" was not found at the experimental dose.

2. control objects and techniques: to control anthracnose, blight, downy mildew, leaf spot, black spot and so on, mancozeb was sprayed at the initial stage of the disease, and then sprayed again after 7-10 days, for a total of 2-3 times.

Thiophanate methyl (thiophanate methyl)

1. Mode of action: thiophanate methyl is a kind of fungicide with high efficiency, low toxicity, low residue, broad spectrum and internal absorption, which has both protective and therapeutic effects. Its mechanism is that when the drug is sprayed on the plant surface and absorbed by the plant, it is decomposed into methyl benzimidazole-ethyl-carbamate (carbendazim) in the plant after a series of biochemical reactions.

The formation of spindle in the mitosis of interfering bacteria leads to abnormal distortion of germ tube and cell wall of germ tube, which makes the bacteria can not grow normally and achieve germicidal effect. The pure product is colorless crystal, insoluble in water and stable to acid and alkali. It has low toxicity to higher animals, low irritation to skin and mucosa, low toxicity to fish and safe to plants.

2. Control object and application technology: use 70% wettable powder 500 times 700 times. The prevention and control of gray mold, powdery mildew, anthracnose, brown spot and leaf mold all have good prevention and treatment effects. They are sprayed once every 7-10 days for a total of 3 times. Seed treatment can also be carried out with 0.3%-0.4% of seed weight. Or irrigation with 500 times of 70% wettable powder solution to control Fusarium wilt also has a better effect.

4. Chlorothalonil

1. Mode of action: chlorothalonil is a broad-spectrum fungicide, which can replace organic sulfur and copper preparations. It has preventive effect and has no internal absorption and conduction effect. Its mechanism is that it acts with glyceraldehyde 3-phosphate dehydrogenase in fungal cells, binds to the protein containing cysteine in the enzyme, destroys the vitality of bacteria, and destroys the metabolism of fungal cells and loses its vitality.

Chlorothalonil has good adhesion on the surface of plants, is not easy to be washed away by Rain Water, has stable efficacy and long residual period. Pure white crystal, no odor; industrial crystal is yellow crystal, slightly irritating odor, insoluble in water, slightly soluble in acetone and other organic solvents, stable at room temperature, stable to general acid, alkali and UV light, but not resistant to strong acid, resistant to Rain Water erosion, non-corrosive. It is low toxic to higher animals and highly toxic to fish.

2, control objects and techniques: control melon downy mildew, anthracnose, blight, at the initial stage of the disease, spray with 75% wettable powder 500 × 800 times liquid, 1000 kg per hectare, and spray again after 7-10 days; 500 Mel 600 times liquid can control seedling stage sudden fall, blight and other diseases.

5. Ray domino (Metalaxyl, Ruidotoxin, Metalaxan)

The main results are as follows: 1. Mode of action: Redomir is an endobiotic fungicide with upper and lower conduction, which has protective and therapeutic effects. When the agent is sprayed on plants, it can be absorbed by seeds, roots, stems and leaves of plants and transmitted to various parts. So it has both protective and therapeutic effects.

The pure product is white crystal, soluble in water and a variety of organic solvents, stable in neutral and acidic conditions, easy to decompose and fail in the presence of alkali, and the residual period is 10-14 days. Low toxicity to higher animals, no "three causes" to animals under experimental conditions, low toxicity to bees, but irritating effect on eyes and skin.

2. Control objects and techniques: control diseases caused by downy mildew, Phytophthora and rot mold of melons. At the beginning of the disease in the field, 25% metalaxyl wettable powder can be sprayed with 600-800 times liquid, and then sprayed again every 10-15 days, for a total of 2-3 times. If the overcast and rainy weather lasts for a long time, the number of times of application should be increased accordingly. Disinfect the seeds with 35% seed mixer and mix the seeds according to 0.2%-0.5% of the seed weight.

VI. Methyl phosphos

1. Mode of action: this agent is a broad-spectrum internal absorption fungicide suitable for the prevention and control of soil-borne diseases, which mainly plays a protective role, and its adsorption is strong, not easy to lose, and lasts for a long time.

The pure product is white crystal, the original drug is colorless to light brown solid, almost insoluble in water, non-flammable, non-explosive, easily soluble in a variety of organic solvents. It is stable to light, heat and humidity, and has good storage stability. It is low toxic to higher animals and safe to bees and fish.

2. Control objects and techniques: it has strong killing activity against all kinds of pathogens such as half-known fungi, basidiomycetes and ascomycetes, and can be used to control soil-borne diseases such as Rhizoctonia and Silkworm. To control melon seedling blight, soak the seeds with 250 times diluent of 20% EC for 30 minutes, and then spray the concentration solution on the soil surface after sowing.

Copper hydroxide

1. Mode of action: the active ingredient is blue cementitious or amorphous blue powder, and the spherical needling particles composed of six-carbon copper ions can quickly adhere to the crop surface and have long-lasting efficacy. Low toxicity to higher animals. It is a broad-spectrum fungicide, which protects by releasing copper ions evenly on the surface of plants to prevent fungal spores from invading. When the cells of bacteria come into contact with copper ions, they kill them, but have no effect on plants. Therefore, it is a pesticide with no residue and no pollution.

2. Control object and application technology: copper hydroxide can control fungal and bacterial diseases on many kinds of crops, and is suitable for leaf spot, anthracnose, early (late) blight, blight, downy mildew and other diseases of melons.

In the early stage of the disease, 53.8% of the dry suspension was sprayed with 1000 times, or 77% of the preparations were sprayed with 500-1000 times. Because of its excellent solubility, diffusivity and suspensibility, the spread of the disease can be controlled by applying it again every 10 days or so. Under adverse climatic conditions, multiple applications should be considered. To control Fusarium wilt, 77% preparation 500 × 600 times solution was used to irrigate the root.

Copper ammonia complex (copper tetramine sulfate)

1. Mode of action: the pure product is dark blue liquid, which is a highly efficient, low toxic, low residual and broad-spectrum fungicide with strong internal absorption.

2. Control objects and application techniques: 23% water agent 250 × 300 times solution was used to control melon Fusarium wilt, and 14% water agent 250 times 300 times solution could be used to control vine blight, blight and bacterial angular spot. Once every 7-10 days, 2 or 3 times in a row.

9. Kangkuning (Kangkuling, complex ammonia copper. Zinc)

1. Mode of action: Kangkuning has protective effect and certain permeability, but the effect of internal suction treatment is not good. It can be applied to crops to supplement some trace elements, enhance disease resistance, and act directly on pathogens. It has a good control effect on Fusarium wilt of melons. The appearance of this agent is dark blue concentrated solution, generally stable, alkaline case is easy to form precipitation. Low toxicity to mammals.

2. Control objects and techniques: at the initial stage of the occurrence of Fusarium wilt, 25.9% water agent 500,600 times dilution, 250ml per plant, or 25.9% water 1500 ml plus 750kg water per hectare were sprayed. According to the disease interval of 7 to 10 days, even spray 3 times 4 times; can also use 20% water agent 400-600 times, each plant root 250 ml, depending on the development of the disease, once every 7-10 days, continuous pouring 3-4 times.

10. Carbendazim

1. Mode of action: carbendazim is a broad-spectrum, low-toxic, endobiotic fungicide with protective and therapeutic effects. Its mechanism is the formation of spindles in the mitosis of interfering bacteria, thus affecting cell division. The pure product is white crystal, which can be dissolved in dilute hydrochloric acid and acetic acid, and the corresponding salt is Fangmaibao or carbendazim. Low toxicity to higher animals, low toxicity to fish and bees, and safe to plants.

2. control objects and techniques: it is effective for many ascomycetes and half-known bacteria to control melon Fusarium wilt, vine blight, anthracnose, powdery mildew, downy mildew, leaf spot and other diseases. 50% wettable powder 600 × 800 times can be sprayed at the initial stage of the disease, once every 7 to 10 days, for a total of 2 times. Or mix seeds with 0.1% Mel 0.3% of seed weight, or irrigate roots with 500 times solution, 250 ml per plant, or 6 grams per square meter of seedbed for soil disinfection.

The above is the introduction of the types and modes of action of common fungicides. When fungicides are generally used, there are recommended concentrations in the instructions, which can be used according to the instructions. However, it is best to apply according to the concentration put forward by the local plant protection technical department on the basis of efficacy tests. In dry or hot summer, the concentration should be reduced to avoid drug damage.

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