Azoxystrobin, ether oxystrobin, pyraclostrobin, trifloxystrobin, picoxystrobin, enestrobin, etc. These so-called methoxy acrylate fungicides seem familiar, but sometimes It's not easy to figure out their identity characteristics, especially how to use them more reasonably. Below, I will work with you to re-recognize the true colors of these fungicides, which may help to make more rational use in grape production in the future. The story of the discovery of methoxy acrylate fungicides may have been known to many people. But through these stories, there is not only a certain promotional effect on the product, but more importantly, an understanding of the characteristics of each fungicide.
It has long been known that mushrooms born on dead wood can secrete antibiotics to resist the harassment of other microorganisms, but suffer from scientific research restrictions. Until 1969, the Czech scientist Musilek extracted an antibiotic from a mucus fungus mushroom. Mucidin, but still did not figure out its structure. Later, the German team of T. Anke and W. Seglich extracted strobilurin A from another mushroom, followed by oudemansin A, and other researchers extracted myxothiazols and finally proved the first two antibiotics, mucidin and Strobilurin is the same compound. It was already in the 1980s of the last century.
Oudemansin A, strobilurin A and myxothiazols, these compounds have two identical characteristics: both contain (E)-β-methoxy acrylate units; both act on the mitochondrial bc1 complex to inhibit respiration. However, these natural compounds derived from mushrooms decompose when exposed to light and cannot be directly applied to agricultural production.
The predecessor of Syngenta, the predecessor of Jielikang, Imperial Chemical ICI, got the oudemansin A from the T. Anke and W. Seglich research groups in 1982, and invested a lot of manpower and resources to conduct research.
A year later, in 1983, BASF took strobilurin A from the T. Anke and W. Seglich research groups and began research.
The two companies are actually doing the same research, and finally found the same stable and bactericidal activity of the basic compound: enol ether stilbene, referred to as MOAS. This compound consists of a side chain, a pharmacophore and a central linking ring.
ICI (now Syngenta) and BASF discovered the compound and its structure almost simultaneously, but ICI first filed a patent based on the central connecting ring in October and December 1984. Through a series of modifications on the MOAS molecular center connecting ring, the first methoxy acrylate fungicide azoxystrobin with systemic conduction was finally developed in 1992.
BASF did not apply for the same patent until half a year later. Reluctantly, BASF had to go back and re-develop this kind of fungicide from other angles. Finally, by adding a pharmacophore to the compound, the oxime ether group was modified, and the ester was obtained. In 1986, it patented. And its effective date is two days earlier than the ICI patent.
ICI has set a goal for the development of this compound from the outset, which is systemically absorbed and can be transmitted to the top as the plant transpires. To achieve this, they set a lower octanol-water partition coefficient for azoxystrobin and have sufficient metabolic stability in plants.
BASF, which is restricted by ICI patents, has found a highly active oxime ether group variant by studying it on the pharmacophore. Although it cannot be absorbed and transmitted by plant tissues, it has a unique distribution. Characteristics: surface transpiration redistribution. When sprayed on the leaves of the plant, the active ingredient is then secondarily distributed on the leaf surface along the interface between the liquid and the air by gaseous volatilization, so that the distribution of the agent on the target is more uniform and the drug effect is better.
These characteristics of the oxystrobin are very suitable for controlling powdery mildew distributed on the leaf surface, which is exactly the bactericide that BASF has been focusing on. Ever since, the emerald, which focuses on the prevention and control of powdery mildew, has emerged as one of the best products for BASF to prevent and control powdery mildew. Of course, ether oxystrobin is not only effective against powdery mildew, it has a good effect on many fungal diseases. However, ether oxystrobin has one disadvantage, and it degrades rapidly in plants, resulting in a short-lasting period.
For methoxy acrylate fungicides, not only ICI and BASF are intensively researched, but many other companies are also in the process. Japan's Shionogi, also known as Yanyeyi, discovered another pharmacophore similar in function to the thiol ester of oxystrobin, oxime ether amide, and finally developed phenoxystrobin. Later, phenoxystrobin was transferred to Bayer's hands. ICI has since developed a more active trifloxystrobin that has both a thiol ester pharmacophore and an oxime ether side chain. The sputum ester was later transferred to Bayer's hands.
In this way, ether oxystrobin, trifloxystrobin and phenoxystrobin become a group of fungicides with surface transpiration redistribution characteristics, and their vapor pressures are between (2.3-5.5)×10-6 Pa. In the protective treatment, if the application time is early enough, the surface transpiration redistribution property can make the bactericide more evenly distributed on the waxy leaf surface, thereby forming the protection against airborne fungal spores by continuously releasing the active ingredient. Sex barriers, such as powdery mildew.
The logarithmic log POW values ​​for azoxystrobin, fluoxastrobin, picoxystrobin and noxifamine are between 2.5 and 3.6 and have sufficient metabolic stability in plants. These two characteristics make the four fungicides have good xylem mobility, that is, they can be transmitted to the top with the transpiration of plants. Among them, picoxystrobin has surface transpiration redistribution characteristics.
Among all methoxy acrylate fungicides, phenoxystrobin has the lowest logPOW (2.3), the highest water solubility and the lowest water toxicity, allowing it to have both root-intake, apical conduction, intra-leaf residue and Safety of aquatic organisms. However, there is no registration in China.
Pyraclostrobin is BASF's most proud methoxy acrylate fungicide, although pyraclostrobin has neither systemic conductivity similar to azoxystrobin nor surface transpiration redistribution similar to ether oxystrobin The characteristics, but low melting point and high lipophilicity, enable it to be rapidly distributed between the inner layers of the plant leaves, moving across the layers, and mainly concentrated in the vicinity of the epidermis of the leaves, and the distribution of mesophyll cells in the middle of the leaves tends to accumulate less. On the one hand, it achieves its surface protection, and at the same time limits its therapeutic properties. However, the intrinsic activity of pyraclostrobin, the safety of plants and the physiological effects of greening resistance to plants are among the highest in the methoxy acrylate fungicides.
Table 1 List of basic data characteristics of common methoxy acrylate fungicides
For the common diseases of grapes, azoxystrobin, oxystrobin, trifloxystrobin and pyraclostrobin are undoubtedly one of the most commonly used choices, but in view of the characteristics of ether oxystrobin and trifloxystrobin, powdery mildew is undoubtedly It is the best target for prevention and control. If it is used to control gray mold, it is best to use it together with other agents with better systemic properties, such as ether oxystrobin, chlorfenapyr, and chlorfenapyr.
Azoxystrobin has good systemic conductivity and is effective for almost all grape fungal diseases, especially for downy mildew, white rot and anthracnose, which can invade the internal tissues of grape organs. Therapeutic advantages will be revealed, but in order to delay the resistance, it is best to mix with the corresponding other fungicides, such as mixed with enoylmorpholine or organic copper preparations to control downy mildew, with difenoconazole or pentyl Mixture of oxazol and the like for controlling anthracnose and white rot.
In addition, although azoxystrobin has good systemic conductivity, it is still a respiratory inhibitor, and its efficacy is relatively slow. The timing of its use is preferably prevention. Regarding the safety of azoxystrobin on grapes, I believe everyone knows that it is not suitable for blending with silicone additives and emulsifiable concentrates, especially before grape bagging.
For pyraclostrobin, although its systemic conductivity is not as good as azoxystrobin, pathogenic bacteria capable of invading plant organs such as downy mildew and white rot may have a poor effect alone, but pyraclostrobin The effect of the drug is faster than that of azoxystrobin. In the early stage of the disease, it can be used together with a highly sterilizing fungicide to control the disease faster, such as mixing with enoylmorpholine to control downy mildew. In addition, in view of the prominent effect of pyraclostrobin on the green-resistance effect of plants, it is more suitable to use in the germination to flowering stage of grape, and in the high-temperature period after bagging, and it is not suitable to continue to use in the color-changing period and later.
Since pyraclostrobin enters the leaves, it mainly concentrates on the accumulation of the upper and lower epidermis. When using pyraclostrobin, it is not suitable to be blended with silicone additives, and it is not suitable for mixing with highly permeable emulsion preparations, especially in grape leaves. And the young age of young fruit. At present, some foliar fertilizers and biostimulating hormone products are often supplemented with auxiliaries, and it is best to be cautious when mixed with pyraclostrobin. (Old Zhao said agricultural technology)
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