Maize is an important field crop in China. Many corn diseases are encountered during the corn planting process. Among them, corn top rot disease is a common disease. This article will introduce the method of controlling corn top rot disease for For your reference.
1, symptom performance
The 10th and above leaves of the seriously ill strain become brown, rot, and the adhesion cannot be spread into a bullwhip. Some of the diseased plants are wrapped by other leaves when they form a whip, and cannot be stretched to form an arched curl. After dissection, the new leaves and the unextracted tassels were rotted, and the rotted parts were odorous. The stalk anatomy showed no brown lesions in the vascular bundle. The above symptoms can also be expressed on plants in the early stage of the big bell. The white leaf of the light diseased plant is whitened and thinned, and the edge of the leaf is dead, no odor, or only white flowers and dead at the edge of the new leaf.
2, the characteristics of occurrence
According to the investigation of several plots in different regions, firstly, there are differences between the varieties of the top rot of corn rot, and Zhengdan 958 and 浚 å•20 are the most serious, and the occurrence is more common. Second, the plots of low-lying, depressed, and soil-heavy plots are severe. Third, the early plot of summer sowing corn planting is heavier. Fourth, the early stage corn thrips and swedish flies and other heavy insects have a serious incidence. Fifth, the large flare period is less damaging due to the prevention and control of corn brown spot and corn mash sprayed with fungicides and insecticides .
3. Preliminary analysis of the causes of the disease
(1) Isolation and identification of preliminary pathogens. The top rot of corn is caused by a mixture of various fungi and bacteria.
(2) Pests such as thrips and swedish flies are generally heavier on corn, and the resulting wounds open the way for the invasion of pathogenic bacteria. From the top, it was dissected from the outside to the leaf by leaf: in 69 strains, the strain rate of the thrips was 45%, and the insect amount per plant was 1-8, with an average of 4.5: the larva of the Diptera insect Or the rate of larvae is 7.2%, the number of larvae or pupa is 3-10 heads; the rate of worms of corn mash is 17%, and many stalks are harmed.
(3) Suitable climatic conditions. During the big trumpet period of corn, there is much rain, high temperature and high humidity. The accumulated water in the trumpet of the plant is beneficial to the infection of various fungi and bacteria, and can be spread by wind and rain. In recent years, the corn seedlings are mostly dry and rainy, and pests such as thrips and swedish flies are generally heavier, which not only causes damage during the seedling stage, but also causes aggravation of pathogenic bacteria invading the wounds in the middle and late stages. After the drought in the seedling stage, heavy rain suddenly occurred before and after the big trumpet period, and the growth rate of the corn increased rapidly in a short period of time. The micro-injury caused by this was also conducive to the invasion of pathogenic bacteria.
(4) There is a difference in resistance between varieties. The Zhengding 958 and the Shandan 20 showed severe rot at the top, which occurred more commonly. Xing Kang 2 under the same environmental conditions was relatively light.
(5) Pathogens are widely present.
4. Emergency prevention and treatment methods
(1) Prevention and control of pests such as thrips and swedish flies during seedling period. At the time of sowing, the seeds are mixed with seeds and sprayed at the seedling stage. The agent can be selected: 5% acetamiprid 1500 times solution, 10% imidacloprid 2000 times solution, 48% chlorpyrifos emulsifiable concentrate 1000 times solution, 1.8% avermectin emulsifiable concentrate 2500 times solution, 10% beta-cypermethrin emulsifiable concentrate 1500 times solution and the like.
(2) Prevention and control of the large bell mouth in the early stage. In the early stage of the disease, the main control bacteria and fungi should be combined with foliar fertilizer . The selected agents are: 72% agricultural streptomycin sulfate or neomycin, or 2000 times liquid + 50% carbendazim. Wet powder 500 times solution (or 70% thiophanate 1000 times solution, 75% chlorothalonil WP 500 times solution) + high quality foliar fertilizer 1000 times solution (or 1% urea water + 0.3% dihydrogen phosphate) Potassium solution) is applied evenly, emphasizing that the liquid reaches the diseased part, especially the top heart leaf and the newly grown leaves. Corn brown spot can be controlled at the same time. If the corn borer, cotton bollworm and other pests also need to be controlled, the corresponding insecticide can be sprayed together according to the instructions.
(3) Remedies in the middle and late stages. For severely ill strains, the "bull whip" formed by the top leaves of browning, decaying and adhering can be cut off to facilitate the extraction of the tassels, and the cut diseased leaves are taken out of the field for deep burial treatment, and sprayed as soon as possible. .
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