Summer maize is about to be pollinated after entering August. The major pests in the middle and later stages of corn include corn top rot, brown spot, stem rot, corn borer (corn borer), cotton bollworm, armyworm, and corn borer.
I. Symptoms of major pests in maize
1, corn brown spot
In recent years, new diseases have become common. The disease usually begins when the corn has 8-10 leaves. The early stage of disease is on the lower 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, corn top rot
Maize 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 heart of the victim plant is rotted and tightly wrapped from the base of the leaf. A serious hand can pull out the entire heart and leaves, and the distortion of the heart of the mildly ill plant cannot be developed.
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 from wounds, stem nodes, young leaves, and other young tissues, especially if they are harmed by thrips, swans, aphids, etc., which 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 (boring insects)
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, commonly known as “flower leaves. The ear of corn is damaged during the late growth period, and the stems are damaged and the nutrition is destroyed. The transport of substances has a serious impact on corn production.
4, three generations of armyworm
Mythimna separata is characterized by immobility and local concentrated outbreak. Its occurrence is affected by weather conditions, especially local microclimate. If the downdraft is encountered during the southern migration of the armyworm, it will cause a large number of adult insects to fall and cause local concentrated outbreaks.
5, four generations of cotton bollworm
The fourth-generation H. armigera is a serious pest that damages corn except corn borer. The damage to the ear of maize is serious (ear rot). Not only increases the degree of harm, but also affects the quality, so the control of the bollworm is very important in the later period.
Second, prevention and control technology
Due to the large planting density of summer maize and the plants in the middle and late stages are already too high, the plant protection drone can be fully utilized to carry out the “one-spray and multi-effect†fly prevention operation in the middle and late stage of corn pests to achieve the effects of disease prevention, pest management, stress resistance, and yield increase. "One spray and multiple effects" of corn should focus on the application of "prevention technology" promotion. The timing of prevention and control is after August 15 (after pollination of corn).
Recommended "a multi-effect spray"
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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