Azoxystrobin, acetostrobin and pyraclostrobin should be the most popular fungicides in the past two years. Their ancestors are extracted from a kind of mushroom, and they all belong to the methoxyacrylates.
What' s the difference between them both being called "mycoesters"?
The three fungicides all have the functions of protection, treatment, and eradication. The biggest difference is that azoxystrobin is less mobile than the other two, pyraclostrobin is more active than the first two, and azoxystrobin is more permeable.
If these three fungicides were developed on the same day, everyone's understanding of them would definitely not be as high as today, because they are really similar.
The reason why some people say that fenoxystrobin has not been very effective in the past two years is because fenoxystrobin was developed earlier and resistance has increased.
Pyraclostrobin is the newer compound, less resistant and most active.
In terms of early control effects, azoxystrobin and pyraclostrobin are evenly matched, and their later therapeutic effects are equally matched. Due to the good systemic mobility of azoxystrobin and pyraclostrobin, these two are more useful in practical applications.
However, if you increase the amount of water used in the spray of fenoxystrobin and spray it more evenly, the effect will not be much different.
The medicine is very effective, but it cannot be used alone for a long time.
In the eyes of many people, these three "mycoesters" have a wide bactericidal spectrum and are very effective in treating diseases. They are used frequently in places with high drug levels. Little do they know that this is simply a waste of the powerful effects of these fungicides.
The magic of methoxyacrylate is that it can strongly inhibit the germination of bacterial spores.
Now that we understand this, let's talk about how to best use it.
(1) This type of fungicide is best used before the spores germinate. Although this is unrealistic, no one will spray the fungicides before the lesions are seen, and it is so expensive.
(2) If an illness occurs, the most important effect of using this type of fungicide is to prevent the growth of pathogen hyphae and prevent secondary contamination of spores, rather than directly and quickly killing the bacteria.
(3) Please try to reduce the number of times you use this type of agent. Their action site is very single, and resistance develops quickly. You can use it three times in a season.
Don't expect to use it alone to kill bacteria. The activity is really not much different from other targeted fungicides, but the prevention effect and duration of effect are much better.
Therefore, a single agent cannot be used for long-term treatment. It is best to use it with other fungicides or to use a compound agent.
Of course, these three types of products cannot be used together. It is wasteful and will not have much effect.
Strong permeability is also a problem
These three fungicides have strong penetrating properties.
(1) When azoxystrobin was first promoted, it was clearly stated not to be mixed with silicone and emulsifiable concentrate. This is why it should be used with caution in the seedling stage.
Known phytotoxicity: Azoxystrobin will cause phytotoxicity on Gala apples, and azoxystrobin + EC will cause phytotoxicity on Shanghai Qing.
(2) Pyraclostrobin is relatively miraculous and the chance of drug harm is low.
In short, the strong permeability allows this type of fungicide to be well compatible with the surface of leaves, greatly improving the control effect and duration, but it also puts forward higher requirements for the safety and usage of individual products.
Registration scope and dosage of 3 fungicides
Azoxystrobin
Can be used to prevent and treat 33 diseases.
Vegetables:
Tomato early blight, late blight and leaf mold; cucumber downy mildew, powdery mildew, scab and vine blight; winter melon downy mildew and anthracnose. Luffa downy mildew; pepper anthracnose and blight; potato late blight, early blight and black mole disease.
Fruits:
Grape downy mildew, white rot and black pox; citrus anthracnose and scab; watermelon anthracnose; lychee downy mildew; banana leaf spot; mango anthracnose.
Field type:
Soybean rust; rice blast and sheath blight, etc.
Take the prevention and control of tomato late blight, leaf mold and cucumber powdery mildew, scab and vine blight as examples:
Start spraying at the early stage of the disease, and use 60 to 90 g of azoxystrobin 250 g/L suspension preparation per acre (15 to 22.5 g of active ingredient) mixed with water and spray. Apply once every 7 to 10 days, with a safety interval of 5 days, and use it up to 3 times per season.
Acetostrobin
The bactericidal spectrum is not as broad as azoxystrobin, but it has specific effects on powdery mildew and other diseases. Meprostrobin has been registered on 15 crops in my country and is used to control 13 diseases.
Vegetables:
Cucumber powdery mildew; tomato early blight.
Fruits:
Strawberry powdery mildew; apple powdery mildew, spotted defoliation and scab; pear tree scab; grape downy mildew; banana leaf spot, etc.
Field type:
Wheat powdery mildew and rust,
Take the prevention and control of strawberry powdery mildew as an example:
Start spraying before the onset of the disease or in the early stages of the disease, and spray with 3000 to 5000 times of distrostrobin 50% water-dispersible granules (effective concentration 100 to 166.7 mg/kg). Spray once every 7 to 14 days, with a safe interval of 5 days, and use it up to 3 times per season.
Or use 30% to 40 g of 30% wettable powder preparation of fenacetostrobin (9 to 12 g of active ingredient) mixed with water and spray. Use once every 7 to 14 days, with a safe interval of 5 days, and apply the pesticide up to 4 times per season.
Pyraclostrobin
It has the strongest relative antibacterial activity, has a strong ability to inhibit the germination of pathogen spores, and has potential therapeutic activity, and can be used to prevent and treat a variety of crop fungal diseases.
Pyraclostrobin has strong conductive activity in plants, which can improve crop physiological functions and enhance crop stress resistance.
Vegetables:
Cucumber powdery mildew and downy mildew; cabbage anthracnose.
Fruits:
Watermelon and mango anthracnose; Banana scab, anthracnose, leaf spot and shaft rot.
Field type:
Lawn brown spot; tea tree anthracnose; corn spot and plant health effects, etc.
Take the prevention and control of cabbage anthracnose as an example:
Start spraying before the onset of the disease or at the early stage of the disease. Use 30 to 50 mL of 25% pyraclostrobin EC per acre (active ingredient 7.5 to 12.5 g) mixed with water and spray. Apply once every 7 to 10 days, with a safe interval of 14 days, and use it up to 3 times per season.
Pay attention to the risk of resistance when using
1. Methoxyacrylate fungicides are all at high risk of resistance and are cross-resistant to each other.
(Even if any one of azoxystrobin, acetostrobin or pyraclostrobin is used, resistance to all three fungicides will occur at the same time);
With long-term continuous use, the resistance of pathogenic bacteria will rapidly increase, which is the main reason why the effectiveness of azoxystrobin and acetrostrobin in disease control has been generally reported to have declined in recent years.
2. From the perspective of resistance management, the total number of applications of methoxyacrylate fungicides such as azoxystrobin, acetostrobin or pyraclostrobin should not exceed 3 to 4 times during each crop growing season; it should be used alternately with other fungicides with different mechanisms of action (such as triazoles, etc.).
