Grape downy mildew has strong infectivity, rapid spread and rapid occurrence, which not only harms leaves, but also infects tidbits, fruit axes and fruit grains, not only destroying gardens, but also directly destroying production.
Over the years, due to the unscientific and irregular use of drugs by fruit farmers, especially the continuous and excessive use of a single component, the resistance to downy mildew is complicated at present, and the actual control effect of many drugs is unstable, which brings many difficulties to disease control.
The author summarizes the actual situation of downy mildew control in first-line orchards in recent years, and tries to do this article with the toxicological analysis of pesticides, hoping to help the majority of fruit farmers.
I. Classification of drugs
Drugs for preventing and treating grape downy mildew can be divided into four categories according to their functions: protective agents, therapeutic agents, plant immune activators and plant growth stimulators. Each category has its own unique functions and application requirements.
1, protective agent
Before pathogen infection, agents that prevent pathogen infection and protect crops from pathogens are called protective fungicides.
Commonly used protective fungicides include copper preparation (Bordeaux solution/copper quinoline/copper abietate), mancozeb/propineb/metsulfuron-methyl, captan, azoxystrobin, azoxystrobin/pyraclostrobin, etc. Two problems must be paid attention to when using protective fungicides to control grape downy mildew:
Protective fungicides must be used before the onset to avoid downy mildew, and most protective agents have no obvious effect after the onset. Because downy mildew mostly occurs after rain, it is the key to prevent the disease by using protective agents before continuous rainfall.
Protective agents generally have poor internal absorption and conduction ability. After spraying, a layer of drug film is formed on the surface of plants. Where the drug film covers, the drug effect can be exerted to avoid infection. However, pathogens can still infect leaves without drugs attached. Therefore, the use of protective agents must be even and thoughtful, especially the grape downy mildew is infected through the back of leaves, so the back of leaves is the focus of medication.
2. Therapeutic agents
After bacterial infection, drugs that can prevent bacteria from continuing to develop and eventually lead to the death of bacteria are called therapeutic fungicides. Most therapeutic agents generally have systemic conduction function, which can enter plant tissues after spraying and kill infected bacteria.
Common therapeutic fungicides include triethylaluminum phosphate, metalaxyl, cymoxanil, propamocarb, dimethomorph, etc.
Chlorobromoisocyanuric acid has broad bactericidal spectrum, quick response and no systemic activity, but it is effective against downy mildew and can also be used as a therapeutic agent.
Ershuangling used to be the mainstream drug to prevent downy mildew, but because of the drug resistance of bacteria, it has actually lost its control effect, so I will not introduce it here.
_ Azoxystrobin, difenoconazole, flupyrazole, thiabendazole, fluazinam, bensulfuron-methyl, indazolamide and other ingredients have therapeutic effects on downy mildew, but the above ingredients have not been localized and the use cost is high, so this article will not introduce them in detail.
3. Plant immune activators
Plant immune activator is a kind of pesticide, which has been developed in the international market for many years, but it has not had a molding effect in China.
As the name implies, plant immune activators, like vaccines, can activate or enhance the resistance of crops to a certain kind of diseases by being used before the occurrence of diseases, thus avoiding or reducing the occurrence of diseases.
The core advantages of plant immune activators are long duration, difficult to produce drug resistance, reliable control effect, no risk of pesticide residues and high safety. However, plant immune activators should pay attention to the following two points in application:
It takes a certain time and process to activate the immune function of plants and improve their resistance to certain diseases. Therefore, plant immune activators must be used one week before the onset of crops to achieve disease-resistant effects;
Plants need to consume certain nutrients to improve their disease resistance, so it is necessary to strengthen the fertilizer supply of crops while using plant immune activators.
At present, there are few plant immune activators in China, among which benzothiadiazole is more mature for grape downy mildew.
4. Plant growth stimulator
Plant growth promoter is the fastest developing project in the field of pesticides in recent years. The core function of plant growth stimulator is to activate the production capacity of plants by strengthening their absorption capacity and nutrient synthesis capacity. This also includes improving the resilience of plants, that is, the ability to resist adverse growth environment and pests and diseases.
At present, seaweed extract and phosphite fertilizer are ideal for grape downy mildew.
1911October 29th, 20 16 10, the vitality element mentioned at the end of Liu Weiping's "downy mildew of grapes", is the essence of seaweed produced by American Gaole. Betaine and mannitol contained in seaweed extract can improve the disease resistance and resilience of plants, and polyphenol polymers in seaweed extract have high bactericidal activity. Practice has proved that continuous use of seaweed essence before crop disease can really achieve the effect of strengthening growth and reducing disease.
Phosphite compound is a phosphate fertilizer. After spraying phosphorous acid, it can play an oxidative sterilization role on the plant surface and has a certain effect on downy mildew. Common phosphites are potassium phosphite and calcium phosphite. The basic premise of downy mildew is the ratio of nitrogen and potassium in leaves, that is, increasing the content of potassium in leaves can improve the resistance of grapes to downy mildew. Therefore, potassium nitrite can not only be used as foliar fertilizer, but also be used in combination with pesticides to consolidate the control effect of downy mildew.
Second, drug analysis
The advantages of protective fungicides are long duration and broad bactericidal spectrum, and most of them can prevent and control many diseases at the same time. The disadvantage is that protective fungicides must be used before the disease of crops, and the effect is not good after the disease.
1, preparation of copper
/kloc-More than 0/00 years ago, fruit farmers in Bordeaux, France, sprayed mixed solution of copper sulfate and lime on grapes to prevent passers-by from stealing grapes, which inadvertently opened the precedent of modern pesticides and gave birth to the first chemical pesticide-Bordeaux mixture.
After spraying copper preparation, copper ions will be released slowly on the surface of leaves. After copper ions come into contact with pathogens, they will have an oxidative sterilization effect on pathogens, thus preventing the infection of pathogens.
The bactericidal activity of copper preparation depends on the concentration of copper ions, and the safety and duration of copper preparation depend on the release rate of copper ions. For example, after spraying Bordeaux mixture, the release rate of copper ions is affected by the weather. The higher the humidity, the faster the release rate, which is the reason why Bordeaux mixture is prone to phytotoxicity in rainy season. Copper quinoline, copper rosin acid and other products, after spraying, the release speed of copper ions is stable, not affected by the weather, the duration is more stable and the safety is better.
Copper rosin acid has the advantages of low cost, broad bactericidal spectrum and stable control effect on downy mildew, but it has poor effect on fruit diseases such as white rot. Copper oleate has one advantage: strong adhesion to leaves after spraying, strong film-forming ability and rain erosion resistance.
Quinoline copper is a new generation of organic copper preparation with better safety and more stable duration. The use cost of quinoline copper is higher than other copper preparations. One advantage is that the compound can not only be sterilized by copper ions, but also has a wide range of bactericidal activities. Therefore, copper quinoline has more obvious advantages in safety and broad spectrum.
2. Mancozeb/propineb/amobam
Mancozeb, propineb and thiram have the same action mechanism and broad bactericidal spectrum, which can prevent and cure all fungal diseases that may occur in grapes for a long time, but these components have no systemic activity, so spraying must be uniform and thoughtful, especially on the back of leaves.
Among the three pesticides, mancozeb has the dominant control effect and a long duration. However, this component may be harmful to some Eurasian varieties, especially not recommended for red extraction.
The control effects of propineb and thiram are not as good as mancozeb, but they are safer and can be used by all varieties. These two ingredients can prevent diseases,
It can play a certain role in supplementing zinc to leaves.
3. Cronidan
Coladan is a protective fungicide, and its sales volume has increased rapidly in recent years. Compared with mancozeb, there is no obvious difference in duration and control effect, because the use cost of clonidine is higher and the overall cost performance is not as good as that of mancozeb.
The safety of captan is better than mancozeb, and it has an additional advantage, that is, the fruit surface can be optimized after using this ingredient.
4. Azoxystrobin/pyraclostrobin
Azoxystrobin is the most popular ingredient among fungicides in the world. Its functional advantage lies in its broad bactericidal spectrum, effective against common fungal diseases, systemic effect in leaves, and obvious duration advantage.
Azoxystrobin is a protective fungicide, which must be used before the obvious onset of grape downy mildew. Azoxystrobin has certain safety risks and should not be mixed with silicone or emulsifiable concentrate products.
In recent years, pyraclostrobin has achieved localization, greatly reducing the cost of medicine, and has a good application prospect in grapes. The composition has good safety, not only has a protective effect, but also has a certain therapeutic effect, and can be used not only before onset, but also in the early stage of onset.
Azoxystrobin and pyraclostrobin can increase the activity of nitrate reductase in plants, thus increasing the supply of nitrate nitrogen. In particular, these two components can reduce the ethylene content in plants. The advantage is to avoid premature senescence of leaves and maintain the nutritional synthesis ability of functional leaves, while the disadvantage is to delay ripening, which should be paid attention to during grape coloring period.
5. Cyanoxazole
Cyanidazole has a narrow bactericidal spectrum and can only be used to control downy mildew on grapes. Cyanidazole is in the process of localization, and its use cost will be greatly reduced in the future, making it the mainstream choice to control downy mildew.
The core advantage of cyazofamid is its high activity against downy mildew, and its duration is generally better than other components. It is one of the most persistent fungicides to control downy mildew. However, the defect of triazole is poor conductivity, so the medication must be thoughtful and meticulous.
The therapeutic agent is more flexible and can be used in the early stage of downy mildew. These agents generally have systemic conduction activity, and most components are good at rapid action. However, due to the single mode of action of most therapeutic drugs, bacteria are prone to drug resistance, so the local actual drug resistance problem must be considered when choosing therapeutic drugs, and the drug rotation problem must be paid attention to when using drugs.
6. Triethyl aluminum phosphate
Triethyl aluminum phosphate is an ancient systemic conduction therapeutic agent with low price and wide bactericidal spectrum. Besides treating downy mildew, it can also control other common diseases on grapes.
Although the component has been used for many years and its bactericidal activity is average, it is found that downy mildew has no obvious resistance to triethylaluminum phosphate, and its control effect is still reliable. Therefore, in areas with complex downy mildew resistance, triethylaluminum phosphate can be used in combination with other components to ensure the control effect.
At present, it has been reported that triethyl aluminum phosphate has obvious control effect on downy mildew under the condition of root irrigation If it is proved to be reliable, it can greatly reduce the difficulty of using medicine for downy mildew.
7.metalaxyl
Metalaxyl is the earliest component developed for downy mildew in the history of pesticide development, and later it was purified from metalaxyl-metalaxyl -m with higher activity.
Metalaxyl has the advantages of quick response, safe use, strong systemic conduction activity and high bactericidal activity, and once became the mainstream drug to prevent downy mildew. However, the duration of this component is short, so it is not recommended to use it alone. Generally mixed with long-acting protective agent.
The resistance to metalaxyl developed rapidly, but metalaxyl-resistant bacteria reduced their viability in nature and were eventually eliminated. Therefore, metalaxyl is suitable for the first few times of chemical control every year. If it is found that the control effect is declining, other ingredients should be stopped and replaced, and the control effect can be restored by continuing to use them in the next year.
8. cymoxanil
Cymoxanil is still widely used as downy mildew control agent. This component has strong internal absorption activity and is safe to use on grapes. Its outstanding advantages are low cost, quick response and short duration, and it is basically used in conjunction with long-acting protective agents.
Drug resistance has developed in cymoxanil, but there is no report of large-scale drug resistance control failure.
Cymoxanil is suitable for dispensing and mixing with other ingredients to improve the overall quick effect.
9. propamocarb
Propamocarb has good systemic property, good safety and ordinary bactericidal activity, so it must be used in high concentration to achieve the control effect.
Propamocarb is a low-cost drug combination, which can increase the diversity of ingredients and delay the development of drug resistance.
Provincial and municipal law enforcement departments lack effective detection methods for propamocarb, so the risk of counterfeiting in propamocarb is low, so we must identify large production enterprises when buying.
10, dimethomorph/flumorph
At the beginning of the birth of dimethomorph, it was indeed a great revolution in the prevention and treatment of downy mildew. Compared with the previous components, dimethomorph has three advantages: quick-acting, persistent and efficient. At the same time, dimethomorph has spore inhibition activity, which can inhibit the spread and spread of pathogens.
Since the discovery of dimethomorph-resistant strain in Nanjing Agricultural University around 2006, its resistance to dimethomorph has developed rapidly, and the actual effect of dimethomorph on downy mildew is poor at present.
The use cost of dimethomorph is low, firstly, the use concentration can be increased to ensure the control effect; Second, use it in advance, especially in the early stage of onset; Thirdly, it must be mixed with other ingredients, especially with ingredients with better quick effect, such as cymoxanil, or with ingredients with higher activity and longer duration, such as azoxystrobin and pyraclostrobin.
Flumorph is a patented compound in shenyang institute of chemical technology, and its mode of action and bactericidal activity are basically the same as those of dimethomorph.
1 1, chlorobromoisocyanuric acid
Chlorobromoisocyanuric acid is an agricultural fungicide introduced by Nanjing Agricultural University, which has a wide bactericidal spectrum and can kill fungi, bacteria and viruses.
Chlorobromoisocyanuric acid is mainly sterilized by oxidation and has no systemic activity. The biggest feature of this component in controlling downy mildew is that it takes effect quickly, and the layer of Phytophthora infestans will soon dry up after application. The disadvantage is that the temporary solution is not the root cause, and the validity period is short.
If used during the outbreak of diseases, this ingredient can quickly control the development of diseases and reduce the difficulty of disease prevention and control. However, after using this ingredient, it is necessary to apply the ingredients with systemic activity and long duration as soon as possible to consolidate the control effect.
Third, summary.
In this paper, the commonly used pesticides for controlling downy mildew were compared and analyzed in a large space. As far as downy mildew control is concerned, the fundamental measures are to strengthen the supply of potassium fertilizer, promote the development and maturity of leaves as soon as possible, and complete the leaf curtain construction before the rainy season to avoid the vigorous growth and clumping of new branches and leaves.
However, the most effective, direct and labor-saving measure to prevent downy mildew is to build shelter.