How to prevent and treat diseases and pests in middle and late corn

According to field monitoring, the current corn disease has entered its peak period. On July 14 of this year, it entered into the volcano, and it lasted for 20 days. It was hot and humid for a long time and was very conducive to the occurrence of high-temperature diseases. In particular, the field weather conditions favored the size spot, brown spot, curvularia leaf spot, and bacteria. Stalk rot and other diseases are endemic. In order to ensure the normal growth of corn, from now on, we should pay close attention to the prevention and treatment of corn in the middle and late stages.

First, the size of the leaf spot mainly damages the leaves, sometimes invade the leaf sheath and the temporal lobe. In addition to the above-mentioned sites, the small spot disease can also damage the ear. The typical symptoms of corn spot disease are rapid expansion from small lesions to long prismatic large spots, up to 10-30 centimeters in length, and sometimes several lesions are connected together to form irregular large spots. The lesions were initially immersed in water and quickly turned blue-gray, eventually turning brown with dead spots. When the air is wet, black moulds, namely conidial stems and conidia of germs, can grow on the lesions. The onset condition of the leaf spot is temperature 26°C-32°C. Under high humidity conditions, low-lying land and high density in the field are susceptible to disease. The pathogenic bacteria reproduce on the foliage and re-infestation by wind and rain. The suitable temperature of the pathogen is 20°C~28°C. When the relative humidity of the air is more than 90%, it will facilitate the breeding of pathogens. Temperatures above 25°C or below 15°C, relative humidity below 60%, disease is suppressed. Corn jointing - heading period in case of continuous rain easily popular.

Second, brown spot occurs mainly at the junction of the leaf base and leaf sheath, but also damages the leaves, leaf sheaths and stems. At the beginning, the lesions were yellowish-white, round, spotted, and later expanded into brown or purple, slightly bulging into bubble-like round plaques. The lesions were reddened around the lesions, and lesions on the midribs or leaf sheaths were slightly larger. The big bell-mouth period is the susceptible stage of corn brown spot, which is currently common and there are significant differences between the varieties. The suitable temperature for corn brown spot disease is 23°C~30°C, and the rainy weather during the middle and late stages of corn growth is more prone to the epidemic under high humidity and high temperature conditions.

Chemical control can be used 20% of Triadimefon EC 3000 times or 12.5% ​​diniconazole powder 30g, spray 30 kg of water.

Third, Curvularia leaf spot The disease mainly damages the leaves, and sometimes also damages the leaf sheath and the temporal lobe. The sickness is a small spot of primary chlorosis. It gradually expands into a round to faded transparent spot. The middle is white to yellow-brown and the edge is dark brown. There are light yellow halos around, and the symptoms vary greatly. Some have only some white or brown dots. This disease is another serious disease following the corn spot disease. When the high-temperature season of July to August, there are 4 to 5 days of rain, the disease may be popular.

Chemical control can be used 50% Tuzet WP 1000 times or 12.5% ​​Tepuzole WP 4000 times, also can use 70% Mancozeb WP 1000 times for foliar spray, interval 7 ~ 10 The second time of the day spray, even spray 2 ~ 3 times is appropriate.

4. Bacterial stalk rot mainly manifests itself in sudden death of plants during the middle growth period. Usually, the indirect part of the ground surface produces yellow-brown to dark brown water stains and soft, subsiding ulcerations, often with unpleasant odors. The disease occurs during corn trumpet. The average temperature of 30 °C, relative humidity of more than 70%, damp and hot weather conducive to disease.

The agent can be used 3000 times 85% trichloroisocyanuric acid, again for 7 days.

Note: In the prevention and control should be taken into account. Diseases and insect pests will be mixed on the same plant during the middle and later stages of corn growth, and one drug and multiple effects and one spray and multiple defenses should be considered when selecting drugs and applying pesticides. Such as spray insecticide mixed broad-spectrum fungicide (such as diniconazole, carbendazim). In the disease prevention and treatment pharmaceuticals, foliar fertilizers such as Penshibao, Duoxin or potassium dihydrogen phosphate may be added at the same time, which can promote the recovery of corn and increase disease resistance. Generally, it is administered once every 7 days or so, and 2 to 3 times of continuous medication is used.

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