Detailed Explanation of the Characteristics of Several Common Fungicides

1. Bordeaux mixture. It is a good protective fungicide, prepared from copper sulfate, quicklime and water. According to the different amounts of copper sulfate and quicklime used, it can be divided into several types: equal formula (1:1), half-strength formula (1:0.5), high-copper formula (1:3) and double-strength formula (1:2). When preparing, first dissolve the copper sulfate and quicklime separately in half of the water, then pour the copper sulfate into the quicklime solution and stir evenly with a stick. The prepared Bordeaux mixture is a sky-blue colloidal suspension, alkaline, with strong adhesion, capable of forming a thin film on the plant surface, and its effective period can last about half a month. Bordeaux mixture does not keep well in storage and must be prepared and used on the spot; it cannot be mixed with pesticides that are incompatible with alkaline substances. It can control black spot, rust, downy mildew, gray leaf spot and many other diseases. 2. Lime sulfur mixture. It is also a protective fungicide, made by boiling quicklime, sulfur powder and water in a ratio of 1:2:10. The stock solution is a dark reddish-brown transparent liquid with a rotten egg smell and is alkaline. When preparing, first bring the water to a boil in a pot, pour in 1 part quicklime, and after the lime dissolves, add 2 parts sulfur powder that has first been mixed into a paste with a small amount of water, stirring while adding. After adding, boil over high heat for about 1 hour, and when the liquid turns reddish-brown, stop the fire. After cooling, filter out the sediment to obtain the lime sulfur mixture stock solution, whose Baume degree is generally 20-24. The stock solution must be diluted before use. For spraying during the dormant period, Baume 3-5 degrees can be used, while during the growing period only a dilution of Baume 0.3-0.5 degrees can be used. It can control powdery mildew, rust, downy mildew, shot hole disease, leaf spot and many other diseases, and can also control pests such as whiteflies, spider mites and scale insects. 3. Chlorothalonil. It has protective and therapeutic effects, a broad fungicidal spectrum, and a long residual effect, and it is irritating to the skin and mucous membranes. A 600-1000 times dilution of the commonly used 75% chlorothalonil wettable powder is sprayed to control rust, downy mildew, powdery mildew, black spot, anthracnose, blight and other diseases. It cannot be mixed with strongly alkaline pesticides. 4. Carbendazim. It is a highly effective, low-toxicity, broad-spectrum systemic fungicide with protective and therapeutic effects and a long residual effect. Generally, a 1000-1500 times dilution of the 50% wettable powder is sprayed to control brown spot, sclerotinia rot, anthracnose, powdery mildew and other diseases. It can also be used for seed dressing and soil disinfection. When dressing seeds, the amount used is generally 2-3/1000 of the seed weight. 5. Thiophanate. It is a highly effective, low-toxicity, broad-spectrum systemic fungicide with protective and therapeutic effects and a long residual effect. Its fungicidal spectrum and efficacy are similar to those of carbendazim, with low toxicity to humans and livestock and safety for plants. A 500-1000 times dilution of the commonly used 50% wettable powder is sprayed to control powdery mildew, anthracnose, sooty mold, southern blight, sclerotinia rot, leaf spot, gray mold, black spot and other diseases. Thiophanate-methyl is also commonly used. 6. Zineb. It is a broad-spectrum organic sulfur fungicide, light yellow, with a slight odor, and it decomposes very easily in air or sunlight. A 400-600 times dilution of the commonly used 65% wettable powder is sprayed to control brown spot, anthracnose, damping-off, shot hole disease, gray mold, powdery mildew, rust, leaf blight, stem rot and other diseases. It cannot be mixed with alkaline agents or agents containing copper or mercury. 7. Tuzet. It is a mixed fungicide of organic arsenic and organic phosphorus, a white powder, poorly soluble in water, easily soluble in alkaline solutions, and easily decomposed in acidic, high-temperature and humid environments. Generally, a 1000-1500 times dilution of the 50% wettable powder, or a 2000-2500 times dilution of the 80% wettable powder, is sprayed to control anthracnose, rust, stem rot, powdery mildew, sclerotinia rot and other diseases. 8. Benlate. It is a broad-spectrum systemic fungicide with both protective and therapeutic effects, insoluble in water, with a slight irritating odor and a long effective period. A 2000-5000 times dilution of the commonly used 50% wettable powder is sprayed to control gray mold, anthracnose, powdery mildew, sclerotinia rot and other diseases. 9. Amobam. It has strong fungicidal power and both protective and therapeutic effects, and after decomposition it also has a certain fertilizing effect. It is a light yellow liquid. A 1000 times dilution is commonly sprayed to control powdery mildew, downy mildew and leaf spot, and a 200-400 times dilution can also be used to drench the soil to control stem rot. 10. Streptomycin. It is a white powder. Generally, a concentration of 100-200 mg per liter is used for spraying, root drenching or injection to control bacterial diseases, downy mildew and other diseases. (Xu Maojin)