Summer maize will be pollinated after entering August. The major diseases and pests during the middle and late stages of corn growth include corn tip rot, brown spot, stem rot, corn borer, cotton bollworm, armyworm, and corn borer. August is still a rainy season, climatic conditions conducive to the occurrence of pests and diseases, reminding the majority of corn growers, to do a good job in the middle and later period, "a multi-effect spray" prevention and control work.
First, the main symptoms of corn diseases and insect pests
1. Brown spot. In recent years, new diseases have become common. The disease usually begins when 8 to 10 leaves of corn are found. The disease starts at the lower part of the leaves, sheaths and stems of the corn and gradually spreads to the upper part. The lesions are round or oval, brown or reddish-brown, and later expanded to brown or purple, the lesions are tightly integrated, and the epidermis of lesions ruptures at the late stage of the disease, emitting brown powder. The high temperature and humidity of corn in the later period are beneficial to the disease. Disease occurs.
2. Top rot. Top rot is the general name of corn top rot disease. The symptoms are diverse. It is a new type of systemic invasive disease that has emerged in recent years. The main symptoms are: the victim's heart leaves rot from the leaf base, tightly wrapped, A serious hand can pull out the entire heart and leaves, and the distorted leaves of mildly ill plants cannot be unfolded. Some leaves are chlorotic, transparent, brownish and decaying, and their leaves are short and incomplete. Some blade edges appear as cut-like nicks and yellow stripes and even wither. Pathogens generally invade young tissues such as wounds, stem sections, and heart leaves. In particular, diseases such as thrips, swat flies and aphids will aggravate the disease. High temperature and high humidity are conducive to the disease epidemic. They mostly occur after rain or after field irrigation. The occurrence of low-lying or poorly drained land is heavier.
3. Corn Borer (Brazil). Generally, the young leaves are eaten in the leaves of the heart, and the damaged leaves are translucent, empty, or in rows of round holes, and are mixed with finely-divided insects, known as “flower leavesâ€, and damage the ear, stems, and damage of the corn in the late growth stage. The transport of nutrients has severely affected corn production.
4. Three generations of armyworm. The armyworm has the characteristics of emigration and local concentrated outbreak. Its occurrence is affected by weather conditions, especially local microclimate. If the submerged air flow is encountered during the south migration of the armyworm, it will cause a large number of adult insects to land and cause local concentrated outbreaks. Rainfall at the end of July and early August is more conducive to the infestation of stickworms, hatching of eggs, and survival of larvae. In the past two years, the individual plots were seriously damaged and the leaves were almost bitten. Therefore, the growers should pay close attention to their occurrence and closely monitor their development and prevent and control them scientifically.
5. Four generations of cotton bollworm. The fourth-generation H. armigera is a serious pest that damages corn except for corn borer. The damage to the ear of maize is serious (ear rot), which not only increases the degree of damage, but also affects quality. Therefore, the prevention and control of cotton bollworm is very important in the later period.
Second, prevention and control technology
At present, the planting density of summer corn is large and the plants are too high in the middle and later stages. The plant protection drone can be used to carry out the “one-spray and multiple-effect†fly-proof operation for the middle and late stage diseases and insect pests of maize to achieve the effects of disease prevention, pest management, stress resistance, and yield increase. "Multi-effects" should pay attention to the application of "prevention technology" promotion, prevention and control time after August 15 (after pollination of corn).
Recommend "a multi-effect spray" agents:
Insecticide: 5% A-dimensional saline dispersible granules, 25g/L Lambda-cyhalothrin EC, 5% imidacloprid EC, 70% imidacloprid WP, ​​5% acetamiprid EC, 5% chlorbenzuron Amide suspension.
Fungicides: 80% tebuconazole wettable powder, 10% difenoconazole EC, 70% thiophanate-methyl wettable powder, 25% azoxystrobin suspension.
Foliar fertilizer: urea, nitrogen-containing foliar fertilizer, 5% amino oligosaccharides.
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