Common bactericides and control of pesticides
The following mainly discusses the phytotoxicity and control technology of crops caused by the improper use of fungicides. First, the basic concept of the safe use of fungicides 1, the selectivity of fungicides The selectivity of the bactericidal agent refers to the degree of difference in the activity of the bactericide between the control target and the non-target. The degree of this difference in activity is often expressed as a safety factor. 2, the safety factor of fungicides It is the degree of safety of the bactericide to the plant. That is, the ratio of the highest concentration and the recommended concentration of the bactericide tolerable to the crop. Safety factor greater than 1 can only be used in production. When it is greater than 2.5, it is safer to use. 3 factors affecting the safety factor There are many factors affecting the safety factor, which mainly include the category and nature of the pesticides, crop types (monocotyledonous and dicotyledonous crops) and varieties, crop growth period (vegetative growth and reproductive growth), environment (wet, temperature, pH, etc.), soil quality And micro-ecological systems and other factors affect the safety factor. 4, phytotoxicity type 4.1, generally classified by the time of occurrence of the injury or the nature of the symptoms. According to the time of occurrence of injury can be divided into: Direct phytotoxicity causes phytotoxicity to the current crop after application; Indirect phytotoxicity causes phytotoxicity to the sensitive crops of the lower jaw, such as the phytotoxicity of triazoles on the growth inhibition of the lower dicotyledonous dicotyledon crops and sensitive japonica rice. 4.2, according to the symptoms of injury can be divided into: Obvious damage can be observed in the form of phytotoxicity. This is the problem that people find most easily. Implicit phytotoxicity - no visible symptoms but affecting yield and quality. This phytotoxicity is often overlooked by people. For example, triazoles can prevent the increase of leaf area and reduce the total photosynthetic products; leafy vegetables and fruits become smaller and yields decrease; rice grains may be reduced in grain weight; and the content of unsaturated fatty acids and free amino acids, protein reduction, etc. may be changed. Azoxystrobin can increase the production of toxin of the scab fungus; the heavy metal bactericide also often affects the photosynthesis and reproductive growth of the crop, so that the seed setting rate decreases. 5, drug damage symptoms Developmental cycle changes: emergence, tillering, flowering, fruiting, delayed maturity, and slow growth; Lack of seedlings?? Coating, seed dressing, soaking to reduce the germination rate, or unable to exhume after germination; Discoloration: chlorosis, mosaics, yellow flowers, leaf tip discoloration, or root and fruit discoloration; Morphological abnormalities?? Change fruit shape, plant dwarfing, no heading, flower and fruit deformities; Necrosis, spotting and withering. Second, the phytotoxicity of different types of fungicides and their control strategies (a) Multi-site fungicides 1, the main biological characteristics of multi-site fungicides Generally, the selectivity is poor, and there is no difference or difference in the target between target and non-target organisms. When using, the difference between the tolerance of pathogens and crops to the medicament is mainly used, and the reasonable dose is selected during the appropriate period. This type of fungicide must not have systemic absorption in order to avoid phytotoxicity, and the prevention and control of plant diseases only has a protective effect. If penetrants are added to the process or the particles are too fine to enter the plant through different pathways, it can cause phytotoxicity. The main types and types of multi-site fungicides: Inorganic bactericides (copper preparations, sulfur preparations, etc.), organic sulphur bactericides (Fumei Zinc, Fumeishuang, Fumeijiajiao, Prosin Zinc, Zeisin Zinc, Desenoxin, Mancozeb, dithiocyano methane, etc.), substituted benzenes (pentachloronitrobenzene, chlorothalonil), dicarboximides (procymidone, promethine, sclerotin), phytochemicals Bactericide (ethyl allicin). 2, copper fungicides: including Bordeaux mixture, copper hydroxide, cuprous oxide, cupric chloride, copper ammonia, and so on. Copper and other heavy metal ions can damage cell membrane permeability, passivate proteins, interfere with Mg++ and K+ balance, affect chlorophyll metabolism and respiration, and are not selective. In order to prevent the phytotoxicity of heavy metal ions such as copper, insoluble salts or complex bactericides are generally made to reduce free copper ions. Bordeaux fluid (Bordeaux Mixture) is to react soluble copper sulfate with lime to produce insoluble basic copper sulfate. After use, it gradually releases copper ions under the action of biological and environmental physicochemical functions. This not only extends the validity period, but also increases the security. Cu(SO)45H2O + CaO + H2O→CuSO4xCu(OH)2yCa(OH)2zH2O (xyz varies depending on the configuration method and ratio). However, if insoluble copper salts such as Bordeaux mixture contain excess Ca++ or Cu++, and the use of acids and basic compounds before and after high temperature, high humidity, etc., will accelerate the release of copper ions and cause phytotoxicity. Known for Ca++ Sensitive to Solanaceae, Cucurbitaceae, Grapes, etc.; For Cu++ Particularly sensitive are plum, peach, pear, cabbage, and wheat; apples, Chinese pears, persimmons, soybeans, alfalfa and other crops are more sensitive to Cu++. Symptoms of copper preparations include: chlorosis of leaves of cucumbers, apples, etc., symptoms of mosaicism of leaf buds and leaves of young leaves and leaf margins, and mosaic symptoms of virus-like diseases. Small spots of rust appear on fruits. It can also cause phytotoxicity on rice, some rice varieties are more sensitive, and leaves, especially the leaf margin, are red-brown. Such as copper hydroxide and cuprous hydroxide spray after 2 days can make the tip, leaf edge was purple, or purple spots; 30% copper copper fertilizer 1:400-700 times before spraying in rice 3 days before heading, two days later The Shanyou 422 cultivar had a purple tip and returned to normal after 5-7 days. However, there is no phytotoxicity on 闵香香粳. This kind of injury is related to high temperature and high humidity. Use in Putian can cause yellow seedlings or even dead seedlings. Copper salts cannot be mixed with acid-base compounds, such as lime sulfur, rosin mixture, and mineral oil. Spores cannot be sprayed with limestone in the 15 days after spraying the Bordeaux mixture. Use indoors under high temperature and high humidity conditions. The copper preparations have antagonistic effects when mixed with methicillin and cyanosomes. Fluosilicic acid is strongly acidic, and it has phytotoxicity on peanut leaves under high temperature and high humidity conditions; when used on rice, increasing the dose or causing leaf spotting at high temperatures can also cause damage. Mixed with alkaline compounds easy decomposition failure. 3. Sulfur fungicides: Sulphur is a traditional fungicide that is considered to be safe due to its low cost. It is currently used in large quantities for the compounding of fungicides. In addition there is swelling sulfur (sulfur Bentonite) and lime Sulphur are widely used in production. S In general, it is safe, but it is less effective below 170C. The use of high temperatures above 300C often causes damage to plants. S can replace element O to form toxic H2S in redox reaction instead of H2O can cause leaf spotting. Litholiths can be oxidized or hydrolyzed under weak acids to release S and H2S. Lithosulfide mixture has better disease-preventing effect than other sulfur preparations, but it is prone to phytotoxicity. Different plants have different susceptibility to lime sulfur, such as peach, plum, plum, pear, grape, bean, potato, tomato, onion, ginger, cucumber, melon, etc., and they should be avoided in the hot season. Fruit trees can be used during dormancy. 4. Diterpene octane phenyl sulfonate: This agent will cause bending of asparagus tender stems, and may cause harm to certain flowers (such as roses). 5. Organic fungicide 5.1 Organic bactericides Organic germanium has a strong phytotoxic effect on the reproductive growth stage of plants. For example, the mild phytotoxicity of rice shows that the stems and leaves have dark brown burn spots, small spikes, low grain weight, and when the grains are severe, the grains become blue-green shells or inflorescences, or pods. false. After organic bactericidal agents enter the soil, they are easily degraded by microorganisms into inorganic arsenic residues in the soil. Inorganic arsenic has a strong inhibitory effect on the vegetative growth of plants, and other heavy metal compounds may also cause similar symptoms of phytotoxicity. 5.2 Organic Sulfur Biocide Fumei double is generally safe as a seed treatment, but the use of a slightly higher concentration of cucumber in the greenhouse can cause spotting. A slightly larger dose on apples can easily cause fruit rust. Mancozeb and other high safety, but the young apple fruit can also cause rosacea and other symptoms of phytotoxicity. Because of the destruction of fruit wax deposits, the use of recommended concentrations for the United States Red will cause severe rust symptoms. Desmonsium is weakly alkaline and has the ability to infiltrate plants, so it is very easy to cause phytotoxicity. Mainly the symptoms of burns. 50% water solution is used for rice and the dilution factor should not be less than 1000 times. Generally not used for fruit trees. Dithiocarbamate fungicides (Fumei and Synthetic fungicides) must not be mixed with heavy metal compounds such as copper, nor should they be used in combination with lime sulfur or used within 15 days. Dithiocarbamate and copper preparations often exhibit antagonistic effects. This is the result of the 2:1 coupling of the ammonia remnant to copper ions. 5.3 Substituted benzenes Chlorothalonil is commonly used in the control of fruit and vegetable diseases. However, pears and persimmons are more sensitive and should not be used. At higher concentrations, it can also cause phytotoxicity such as peach, plum, and apple. Use of the apple within 20 days after flowering can cause rust in the fruit. Pentachloronitrobenzene has specific effects on Rhizoctonia, and it is effective against clubroot, blight, and actinomycetes. It is commonly used as a seed treatment and soil treatment agent. Contact with sprouts or leaves of the melons during use may cause burn hazards. (II) Disturbances and control of special-purpose fungicide at a single site The specific biological characteristics of the single-site specific fungicides are highly selective. Site-specific bactericides may be systemic or non-systemic bactericides. Most of the systemic bactericides have a therapeutic effect and possess two unique biological characteristics. First, the drug molecules can enter the plant body through the stems, leaves, seeds or root surface of the plant, and can be transported in the body. Second, its mode of action is specific and effective against pathogens without affecting the host plant. Therefore, a single-point fungicide is generally safer for plants. However, it is worth noting that there are also some improper use of specific fungicides, which may cause different levels of phytotoxicity to different types of plants. The main types of single-site fungicide are organic phosphine fungicides, including different rice bran net, B-aluminum, methyl-triazine, etc.; benzimidazole fungicides, including carbendazim, thiabendazole, thiophanate-methyl, and B Muwei, etc.; amides, such as thifluzamide (full ear); carbamates such as propamocarb; pyrrole such as fludioxonil (Silos); thiazoles such as thiazolyl, tricyclazole; Oxazoles such as hymexazol; methoxymorpholines including dimethomorphs, fluoromorpholine; benzamides such as metalaxyl; antibiotics such as jinggangmycin, polyoxin; dimethylformamides such as snapper Ling, acetaminophen, sclerotium net; anilinopyrimidines such as pyrimethanil; methacrylates such as amidoxime, cuibei; etc.; demethylation inhibitors (DMI) in ergosterol biosynthesis inhibitors Bactericides include triadimefon, diniconazole, propiconazole, tebuconazole, fluorosiliconazole, difenoconazole, prochloraz, chloropyrimidol, and the like. 1.EBI fungicides The growth regulator effects of ergosterol biosynthesis inhibitors often mask their non-specific drug-induced symptoms, such as induced leaf distortion, necrosis, withered or fallen leaves. Triazole bactericides are used as soil and seed treatments. Improper use will result in reduced emergence and seedling rigidity. The elongation of the aerial parts and the elongation of the leaf, root and coleoptile of wheat seedlings were suppressed. Triazole bactericide as a spray treatment will make the melon fruit shape smaller, plant or shoot shortening, internode shortening leaves become smaller, dark green, delay chloroplast aging, improve cold-resistant and drought resistance, increase fruit set rate. Use on rice can cause crop leaves such as rice to be short, and even when heading is severe. Such as the A4 version reported on November 6, 2003 "Pesticides cause trouble The news that 1,466 mu of rice was harvested was not enough. It was reported that no heading and no grouting occurred in rice in Hangji, Yangmiao, and Fair Road in Hanjiang District, Yangzhou City, Jiangsu Province in September 2003. In mid-October, the phenomenon of non-heading rice in this area occurred. A total of 8 townships, 48 ​​villages, and 658 households were involved, and the damaged area amounted to 1,466 mu. According to expert field consultations, the reason why rice was not eared may be due to the inhibition of cell growth substances in pesticides used in the same year. Suqian City and Anhui Province also suffered a similar area of ​​similar phytotoxicity. Whether the reason why rice can't be heading in a large area is related to the use of diniconazole before heading is worth further investigation. It is known that DMI fungicides such as diniconazole are also gibberellin biosynthesis inhibitors that promote cell elongation in plants. The diniconazole used to control powdery mildew in watermelon and pepper seedlings, and caused serious stiff seedlings in Zhejiang and Jiangsu; the symmetrazole zoconazole treatment of early rice seedlings will result in rigidity of post-japonica rice seedlings; treatment with triadimelinol seeds also used to Causes large areas of wheat not to emerge; triazoles spray cucumber, resulting in shortened internodes, leaves and melons shorter. For example, 40% of Fuxing (fluorosiliconazole) 8000-10000 times in the prevention and treatment of pear scab in Shaanxi had the symptoms of leaf curling. DMI fungicides prevent growth regulation or injury mechanisms: (1) The mechanism of triazole fungicides to prevent diseases is to inhibit fungi in vivo Cyt The activity of P450 monooxygenase destroys ergosterol biosynthesis, leading to cell membrane damage and death. It can also inhibit C-14 demethylase Cyt in gibberellin biosynthesis in plants. P450 monooxygenase prevents gibberellin, which promotes cell elongation, from synthesizing, resulting in dwarfing of the plant and short leaf fruit. (2) The direct action of the drug molecules and membranoid alcohol at high doses causes the death of lipid peroxidation cells. The appearance of chlorotic and dead spots on plants. (3) Imidazole fungicides are protonated at physiological pH of the plant, whereas triazoles are non-protonated. The different activities of pesticides on different crops may be related to the physiological pH in the plant. (4) The ABA metabolism associated with gibberellin metabolism is imbalanced and the content increases. ABA has a physiological effect of inhibiting cell elongation. The factors that affect the degree of DMI bactericide harm: (1) plant species and varieties. Generally, dicotyledonous crops are more sensitive to EBI than monocotyledonous crops, so EBI fungicides are more likely to cause phytotoxicity on dicotyledons. Different varieties of the same crop species have different susceptibility to DMI. For example, japonica rice is more sensitive than japonica rice. (2) Pharmaceutical molecules. It is mainly related to the variety and its isomers. Relationship with pharmaceutical varieties: Compared with the control, the treatment of seed treatment with different DMI fungicides at the same concentration inhibited the growth of the 12-day leaf area of ​​cereal crops as follows: imazalil 15%, triadimenol 16%, and C 20% of oxazole, 22% of triadimefon, 23% of chloropyrimidol, 27% of ethiconazole, 28% of benzyl chlorotriazol, and 45% of diniconazole. Relationship with isomers: DMIs generally contain 1-2 asymmetric carbon atoms, so there are 2 or 4 enantiomers, and they often have significant differences in biological characteristics. The R-isomer generally has high bactericidal activity and the S-isomer has strong plant growth regulation (PGR) activity. For example, the bactericidal activity of enantiomer R(-) enantiomer is 100 times higher than that of S(+). The growth regulation of the S(+) isomer is 100% stronger than that of the R(?) isomer Times. The paclobutrazol (S,S)-enantiomer has a high plant growth regulator (PGR) activity, while (R, The R)-enantiomer has a higher antibacterial activity. Relationship with plant tissue: The meristem is extremely sensitive and inhibits cell elongation. 2. methoxy acrylates This is a new type of ultra-spectrum, special high-efficiency and extremely safe low-toxic germicide. For example, Amisida has registered and controlled more than 400 plant diseases in the world. However, there are also a few species that are particularly sensitive and use on these crops can easily cause phytotoxicity. For example, although it is safe to use on apples such as Red Fuji, it is particularly sensitive to use on apple varieties of the clams. It can cause serious symptoms of rust and fruit damage when applied in young fruit, and it can cause fallen leaves when sprayed at high temperatures. Spraying on Yunyan G80 varieties also causes allergic spotting. (C) Seed treatment agent damage and its control 1. Rice seed treatment agent The authors compare the results of the safety studies of several rice seed treatment agents as follows. Pharmaceutical soaking method Soaking time Percentage rate of safety Factor of safety Control object After dithiocyano methane leaching, no panning 24-72 98.8 3 Fungal Bacteria Bataan immersed after panning 48-72 86.6 1.2-1.5 Dry-negative nematodes Prochlorim is not panned after immersion 48 90.3 1.3-1.5 Fungi Crushing after strong chlorine net leaching 12 85.5 1.0 Fungal bacteria It can be seen that the safety factor of net treatment of rice seeds with strong chlorine is very low, and it is extremely unsafe for rice. 2. Seed dressing It has special effects on rust bacteria, smut fungus and Rhizoctonia in basidiomycetes. It is commonly used in seed treatment and soil treatment. Safer against dicotyledonous plants, typically 0.1% of seed -0.3% active ingredient seed dressing. However, monocotyledonous crops are susceptible to phytotoxicity, and treatment with 0.1% of seeds can reduce the emergence rate of wheat by 15%-20%. In case of a bad environment, the harm caused by drugs is heavier. 3. DMI fungicides Including triazoles, imidazoles, pyrimidines, and many other fungicides, due to the high activity of these fungicides and the long residual period, some companies have developed seed treatment agents for such fungicides, which may cause problems in the coating or dressing of wheat seeds. Such fungicides can interfere with the balance of gibberellins (GA3) and abscisic acid (ABA) in plants. In the case of cold conditions, drought, waterlogging, or other stress conditions that are not conducive to seed germination or emergence, significant phytotoxicity can occur. , showing slow seedlings, low emergence rate, or even no seedlings. Fourth, soil treatment agent injury and its control 1. Methyl bromide It is a colorless, odorless, highly toxic, and inactivated liquid compound. 3.5 degrees The above gas volatilizes into a gas heavier than air. Commonly used in soil treatment, a wide spectrum of efficient killing of various organisms in the soil. Including soil nematodes (root knot nematodes, cyst nematodes, rot, nematodes, etc.), a year or perennial weeds and seeds, indigenous fungi and bacteria, soil pests. Soil temperature at 15-20 centimeters After the degree of treatment, covering 48-72 hours after removal of membrane ventilation 7-10 days after sowing or transplanting vegetables. If the soil temperature is low, the ventilation time will be extended, otherwise there will be a strong phytotoxicity to the transplanted crops. 2. Cotton It is converted into methyl isothiocyanate in the soil, and is used as a disinfectant soil treatment agent. Can kill the seeds of plants in the soil. Gully application or application at 20cm Immediately cover the soil and cover the film for a certain period of time. Can not be used during the growth period. The interval between application and sowing depends on the soil temperature. 10 cm soil temperature 25 degrees interval 8 days; 20 degrees interval 11 days; 15 degrees interval 24 days. Generally at a soil temperature of 18-30 degrees, interval 2- Sow for 3 weeks. The best treatment of soil temperature 12-18 degrees, water content above 40%. Crepe Machine,Crepe Making Machine,Crepe Cake Machine,Electric Crepe Maker Guangzhou New Power Catering Equipment Manufacturing Co.,Ltd , https://www.gznewpower.com