How to control wheat scab? The best timing for spraying is key

At present, wheat in various regions has successively entered the heading and flowering stage, which is also a critical period for the occurrence, spread and control of wheat scab and stripe rust.Sowhat are the control methods for wheat scab? When is the best time to spray to prevent wheat scab?

According to expert predictions, this year, because some regions were affected by earlier frost damage, wheat growth is weak and its resistance is poor. Therefore, if preventive work is not done in time, it will lead to a large reduction in wheat yield!

What are the main symptoms of wheat scab?

Wheat scab, also known as wheat ear blight, rotten wheat head and red wheat head, is one of the main diseases of wheat; from the seedling stage to the heading stage, it can all be damaged by it, mainly causing seedling blight, stem base rot, stalk rot and ear rot. The most serious damage is ear rot, which reduces the thousand-grain weight and affects yield; moreover, the toxins secreted by this disease are harmful to the human body. Wheat with a diseased grain rate higher than 4% cannot be sold, so scab is extremely harmful to wheat!

Causes of scab

The pathogen of wheat scab can only infect some spikelets during the flowering and grain-filling stages of wheat, and then spread to the entire ear. What truly causes the disease is a type of propagule called ascospores, which are produced from diseased residues left over from the previous year, including diseased wheat ears, rice stubble and corn stalks.

Secondly, it is a typical climate-type seed disease. Only when rainy weather is encountered during the flowering and grain-filling stages of wheat, and there are large amounts of pathogens (ascospores) in the air, can the disease possibly break out severely. Since large amounts of pathogens exist every year, the weather from the heading stage to the grain-filling stage of wheat, especially the amount and frequency of rainfall, determines the severity of scab occurrence.

When is the best time to spray to prevent wheat scab

For chemical control of wheat scab, spraying should be done as early as possible from the full heading stage to the full flowering stage. If this time is missed, the control effect will be greatly reduced.

Under normal circumstances, wheat first heads and then flowers, so the pesticide should be applied when 10%-50% of flowering has occurred; if the temperature is high during the ear stage and wheat heads and flowers at the same time, the application should be moved earlier to the full heading stage. Spraying should be done before rain. If rain occurs during the key spraying period, spray during a break in the rain.

Generally, spraying once during the key period is sufficient. In cases where the variety is severely susceptible to the disease, or where continuous high temperature and high humidity occur after the first application, or where the wheat growth period is uneven and the flowering stage lasts more than 7 consecutive days, a second application should be made 5-7 days after the first spraying.

Control techniques:

1. Select disease-resistant varieties and achieve reasonable close planting:

Recent market research has found that in many places the sowing rate of wheat is too high, with some places sowing up to 60 jin per mu. After wheat tillering, the wheat layer is thick, ventilation and light transmission in the field are poor, and when air humidity reaches above 80%, it is very easy to cause a major outbreak of scab. In addition, if the wheat heading and flowering stage coincides with more than 3 consecutive days of overcast rain, it is very easy to cause a major outbreak of wheat scab.

2. Using pesticides at the key period can achieve twice the result with half the effort:

Based on many years of control experience, it has been found that the best period for controlling wheat scab is to begin spraying when wheat is at full heading and 4%-6% flowering. At the same time, attention should also be paid to the temperature during the heading stage. When the temperature during the heading stage is high, pesticide can be applied at the full heading stage. If the temperature is low, and wheat first heads and then flowers, spraying should be done at the beginning of flowering.

3. The choice of pesticide is key, combining treatment and protection:

For scab control, fungicides can be selected such as 43% tebuconazole wettable powder or 20% phenamacril · hexaconazole suspension concentrate or 40% tebuconazole · thiram wettable powder or 40% tebuconazole · prochloraz aqueous emulsion or 43% tebuconazole suspension concentrate, etc.; for control of aphids and wheat blossom midges, pesticide varieties with a longer residual effect such as organophosphates and pyrethroids can be selected, such as 48% chlorpyrifos 50-60 milliliters, 4.5% beta-cypermethrin 60 milliliters and other pesticides; at the same time, in combination with the “one spray, three preventions” add 99% potassium dihydrogen phosphate 50-60 grams for mixed spraying, also controlling stripe rust, wheat ear aphids, powdery mildew and premature senescence, using 60 jin of water per mu.

4. Spraying must be scientific and the amount of water must be sufficient:

Especially after wheat jointing, the plant density in the wheat field is high. When spraying, the entire wheat field must be evenly sprayed, and nozzles with good atomization should be selected. When spraying, the lower leaves of the wheat must be thoroughly covered. The amount of water must be sufficient, using 50-60 jin of water per mu. When mixing the pesticide, secondary dilution must be carried out to ensure the effectiveness of the pesticide.

Precautions:

(1) When purchasing pesticides, be sure to buy from regular stores with all “three certificates” complete. It is strictly forbidden to use highly toxic organophosphorus pesticides, high-residue pesticides and their compound varieties.

(2) According to the occurrence characteristics of diseases and insect pests, select suitable pesticide scientific formulas and carry out uniform spraying. When preparing wettable powder pesticides, be sure to first dissolve them with a small amount of water and then pour them into the spraying equipment and stir evenly, so as to avoid pesticide damage caused by uneven liquid.

(3) The dosage must be accurate. Prepare the pesticide liquid according to the dosage per mu and the amount of water, and use standard measuring instruments for preparation. Do not add pesticide at will.

(4) Field spraying should be carried out in the morning or afternoon when there is no dew. If it rains within 6 hours after spraying, it should be re-sprayed.

(5) Strictly abide by the safe operation regulations for pesticide use, do a good job in personnel protection, and after spraying, properly handle pesticide residues and clean the spraying equipment to prevent unsafe accidents such as poisoning of people and livestock.