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According to the long-term monitoring and research of Nanjing Agricultural University and other units, in recent years, the resistance of wheat scab continues to develop, and the distribution area of resistant bacteria expands, posing a threat to wheat yield, quality and food safety.
According to the monitoring of authoritative department, the bacteria group with low resistance to tebuconazole has appeared. As with pyrazolyl ester, carbendazim and other drugs, the use of Tebuconazole in half lethal dose can also increase the production of Gibberella spp. vomitus toxin.
Tebuconazole is the main drug to control scab in large-scale production in recent years. When using the drug to control scab, pay attention to the appropriate period and sufficient application, or mix or combine with other drugs with different mechanism of action, so as to improve the effect of disease prevention, ensure the production and quality.
Carbendazim resistance continues to increase
Many years ago, Fusarium graminearum, which is resistant to benzimidazole fungicides such as carbendazim, appeared in wheat region of East China (Jiangsu, Zhejiang, Shanghai, Anhui and so on). Now, there are a large number of these resistant bacteria in this region, which account for a high proportion in the natural population.
Although the amount of carbendazim was increased in the early stage of the disease, the disease still broke out in rainy days before wheat harvest.
Expansion of the distribution area of drug-resistant bacteria
In recent years, the distribution area of scab pathogens resistant to carbendazim and other benzimidazole fungicides has further expanded.
In some areas of Shandong, Henan and Hubei Province, there are also some strains resistant to carbendazim, especially in the south of Henan Province.
Carbendazim and other benzimidazole fungicides will not only lose the control effect on scab due to the production of drug resistance, but also stimulate the production of toxins, increasing the threat to food safety.
Emergence of Tebuconazole low antibacterial group
Low dose drugs also stimulate drug production
In recent years, it has also been found that the wheat scab strains with low level resistance to triazole fungicides such as tebuconazole have appeared.
In sublethal doses, the use of triazole fungicides such as tebuconazole, and Methoxyacrylate fungicides such as pyrazolyl ether ester, will also make Gibberella bacteria produce more vomitus toxin (Gibberella toxin).
New drugs recommended by experts
Relevant experts think that in areas with frequent occurrence of scab, cyanonenyl ester, phyllostazol (effective ingredient: 15-20g / mu), cyanonenyl ester and tebuconazole (effective ingredient: 16-24) can be selected when wheat is flowering at 5% Gram / mu), thioconazole (effective composition 8~12 g / mu), fluazolam hydroxylamine (effective composition 8~10 g / mu) spraying with water, and spraying 1 times when the flowering reaches 80% ~ 95% (3~5 days before the first application).
Carbendazim, thiabendazole and thiophanate methyl are not recommended to be used in Jiangsu, Anhui, Zhejiang, Shanghai and South Henan where the resistance of scab is serious.
Because wheat scab occurs on the ear composed of multiple spikelets, one spore infection may spread to the ear shaft to cause ear withering, so sufficient water shall be applied during spraying to improve the atomization effect and ensure the uniform drug application of each spikelet.
Adequate use of Tebuconazole
According to the monitoring results and production conditions, the widely used fungicide against Wheat Scab in recent years is still suitable for the control of Fusarium head blight. On the one hand, it is beneficial to kill Gibberella before spore germination and invasion or at the early stage of infection to ensure the disease control effect; on the other hand, it can kill Gibberella as much as possible, reduce the number of virulent bacteria, and reduce the content of Gibberella toxin in commercial wheat.
Tebuconazole and epoxiconazole are two kinds of fungicides which have strong inhibitory effect on crop growth. In the low temperature period, the use of these drugs in large doses, or in a day or two after the application of strong cooling weather, is easy to have adverse effects on wheat heading and filling.
Therefore, do not blindly increase the dosage of these drugs, or use them repeatedly in a short time. The dosage of tebuconazole and epoxiconazole per mu should not exceed 15g, and the interval between two large-scale application should be more than 1 week. The better way is to mix or alternately use these drugs with fluconazole hydroxyamine, cyanoenyl ester, prochloraz, pyrazol ether ester and other drugs which have no inhibitory effect on the growth and development of wheat.
Pay attention to drug conductivity
Prochloraz is not easy to enter the wheat plant after application because of its weak internal absorption and conductivity, so it is not easy to over inhibit the growing tissues and organs of wheat, such as the elongated internodes and the developing flower organs.
When mixed with tebuconazole, the total dosage of azole fungicides can be increased to improve the control effect of scab, and the risk of drug damage is not significantly increased. Prochloraz, cyanoenyl ester, pyrazolyl ether ester and other drugs have poor internal absorption and conductivity. Pay attention to spray them to the ear of wheat as much as possible.
Tebuconazole, fluconazole, propylthiazole, fluconazolyl hydroxylamine and other drugs have strong internal absorption and conductivity. After the drugs are sprayed on the leaves, ears and other parts, they can be quickly absorbed and transmitted to other parts, so that all parts of the wheat plant have medicine. Therefore, they have a more comprehensive protection and treatment effect. The requirements for the application of medicine are relatively low, but they should also be evenly applied as far as possible, so that each wheat plant can get more adequate medicine Quantity.
Make good use of new drugs without resistance
It is a better choice to mix tebuconazole with fluconazole hydroxylamine, propylthiazole, phyllostazol, cyanoenyl ester, pyrazol ether ester and other drugs with different action mechanism.
It is understood that the mechanism of action of albendazole is similar to that of triazole fungicides such as tebuconazole, but they have no cross resistance and can kill the Gibberella spp. which is resistant to triazole fungicides.
The fungicides such as pyrazolyl had strong inhibition on spore germination and initial infection of scab, but had weak killing activity on scab mycelium. It should be mixed with tebuconazole and other drugs in the early stage (from ear opening to flowering). As long as it can effectively control the occurrence of scab, it can naturally reduce the toxin production of scab and the content of vomit toxin in commercial wheat.
The use of new drugs such as yebuconazole, propylthiazole and fluconazole ether hydroxylamine, or their combination with tebuconazole and other drugs, can better kill Gibberella spp. and reduce the production of Gibberella toxin, but the cost of control is relatively high.
In large-scale production, according to the resistance of local Gibberella, weather conditions and the occurrence trend of Gibberella, we can choose the appropriate drug use plan according to local conditions, so as to save cost and increase efficiency while ensuring the effect of disease control, production and quality.
Source: Shuiqing farm
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