Corn large spot disease is most likely to damage corn leaves, what are the pathogenesis of corn larg

Corn large spot disease is a major disease in the Northeast corn planting area with wide distribution, rapid development, serious harm and difficult prevention and control, which occurs to varying degrees every year, resulting in a sharp decline in corn yield, and in severe cases, the yield is reduced by 50-60% or even not harvested. Due to global warming, the number of overwintering bacteria is high, resulting in an increase in the bacterial content in the soil. Coupled with years of continuous cropping and chemical pollution, toxins are ubiquitous in maize plants, reducing maize resistance and increasing maize large spot disease year by year.

First, the incidence of corn large spot disease.

1.Disease resistance of maize varieties.

Disease resistance of maize varieties is one of the factors affecting leaf spot, and the disease resistance of different maize varieties varies greatly. At present, there are many varieties of corn in the agricultural market, including Yuyu 22, Dian Feng 4 and many other varieties. Among these varieties, except for a few varieties with strong resistance to the disease, such as Baoyu No. 7, most of the other varieties have no special resistance to the disease.

2.Effect of fertilizers on leaf spot.

Because of the emergence of various chemical fertilizers, instead of the previous farm fertilizer, most of them are used in the process of planting corn, with little or no farm fertilizer. In addition, in the planting process, top dressing is mainly used in the growing period of corn, and the bottom fertilizer is less when sowing, resulting in uneven soil nutrients, soil fertility decline and even compaction, thereby reducing the disease resistance of corn.

3.Land. Late sowing of maize or insufficient soil nitrogen fertilizer and continuous cropping are conducive to the occurrence and spread of the disease.

Basically, the disease of corn may occur throughout the growth period, the disease at the seedling stage is relatively less, and the disease is relatively more in the middle and late stages of corn growth, especially at the ear stage, and the harm is relatively serious. After the onset of the disease, the leaves of the corn will be scorched in a short time, the plant will die, the ears of the corn will have no grains, the grains will turn black and dull, and the yield and quality will be seriously affected.

4.Temperature coefficient.

The maize large spot disease pathogen can overwinter in the diseased residue, a large number of dormant mycelium will remain in the diseased residue, and other conidia can also overwinter on the diseased residue, and then multiply in the second year, resulting in the disease of the corn plant. During the growing period of corn, the remaining overwintering bacteria on the residue will produce spores, which will float in the wind or splash on the corn leaves in the rain. When the humidity and temperature are right, they can sprout in large numbers on the leaves, causing disease.

After the lesion is formed, under suitable temperature and humidity conditions, a large number of conidia will be produced, which will float in the air and spread with the air current. In severe cases, the entire corn field will be infected.

2. Onset symptoms.

Corn can be infected with leaf spot disease throughout the growth period, especially in the late growth stage of maize, and the disease becomes more and more serious after tasseling. After the onset of the leaves, the lesions appear water-soaked or grayish-green spots. After several days of continuous infection, the venous direction may dilate rapidly, forming large yellow-brown or grayish-brown fusiform plaques with dark brown edges and light brown middle.

The lesions are generally 5-10 cm long and 1-2 cm wide. When the humidity is high after rain or the dew in the field is high, the dark brown mold layer grows densely on the lesions. The disease is severe, and many lesions are interconnected into patches, which can cause early plant death, root rot, small seed wilting, and serious yield reduction.

Outbreak in dry weather, will break out in summer corn earing, the appearance of corn spot, often accompanied by a serious reduction in yield, after timely replenishment of water, will be reduced, to spray, the disease will disappear immediately, but over time, it will appear again.

When it comes to corn spot disease, it is specified that he has a fast onset, a wide range of serious impacts, and a wide range of spreads, which can seriously affect the yield of corn, and its pathogenesis is the above rules.

The pathogenesis of large spot disease of corn is as follows: water-soaked cyan lesions on the leaves, yellow-brown freckles, a large number of gray-black mold layers, scorched leaves, and necrosis marks.

The selected corn varieties have low quality disease resistance, the climate environment is relatively humid, the sowing method is not standardized, the cultivation conditions are not particularly good, and the soil has left a large number of residues of last year's plants, and the fertilization is not in place.

If the quality of the seeds is not very good, the seeds are not disease-resistant, and the soil has bacteria, the temperature is low and the water is too much, and the cultivation system and cultivation conditions are not up to standard, etc., it will lead to the disease.

The humidity is more than 90%, the temperature is around 20-25 degrees Celsius, and the climate is relatively humid. It rains a lot. If the planting density is too large, it will be prone to large corn spot disease.

The environment is too humid, the temperature is too low, the soil nutrients are not enough, the density is high, the low-lying land, and the nitrogen fertilizer is insufficient.

The large spot disease mainly harms the adult leaves of maize, and the lesion form is long fusiform, gray-brown, dark brown at the edge in the later stage, and green wilt color in severe cases. It will harm leaves, bracts, and leaf sheaths, and in addition to the previous points, small spot disease will also harm female spikes and stems, which can lead to fruit rot and stem breakage, so it can be seen that the pathogenicity is stronger than that of large spot disease.

The leaves are infected with water-stained blue-gray spots first. Then expand along the veins of the leaves to both ends, forming large spots with dark brown edges, **light brown or blue-gray, and in severe cases, the lesions fuse, and the leaves turn yellow and die. Select varieties with strong disease resistance, do a good job of land cleaning in time before sowing, and clean up dead branches and leaves; At the beginning of the disease, remove the diseased leaves.

Improve cultivation patterns and control densities. For example, wide and narrow row planting, the planting density per mu is controlled between 4000-4500 plants to enhance the ventilation and light transmission effect.

Try to use as little chemical fertilizer as possible with too much nitrogen. Nitrogen, phosphorus and potassium should be applied in combination. It is best not to plant corn with basic crops, and the growth cycle is the same, but the amount of fertilizer they use is different and the amount of water they use is different.

Corn is a waterlogging-resistant crop. In the drought, the leaves will be rolled, and in severe cases, leaf spot disease will occur. The appropriate temperature for the onset of the disease is 26 32, but the key condition for the onset of the disease is that there is more rainfall and more rainy days in summer.

In the case of low terrain, high plant density, partial application of nitrogen fertilizer, delicate growth, early sowing, etc., the disease is severe, and the application of organic fertilizer, phosphate fertilizer, potassium fertilizer, and intercropping is implemented, and the disease is mild.

Agricultural control measures should be adopted. Before sowing, the seeds should be coated and disinfected. The sowing date is suitable, not too early or too late, and the soil is 5 10 cm when the tillage layer is stable through 12 degrees.

If the soil is heavy clay, it is necessary to pay attention to the loose moisture in the tillage, and the stagnant water in the field should be eliminated in time. Clean up the field in time after the autumn harvest to reduce the diseased plants left in the field; Deep ploughing before winter to promote plant residue decay; At the beginning of the disease, the diseased leaves at the bottom of the plant are removed. Plantar fertilizer was applied, phosphorus and potassium fertilizer were applied to improve plant disease resistance; Intercropping with other crops to improve the ventilation conditions of corn fields and reduce the infiltration of pathogenic bacteria.

After 10-14 days, conidia can be produced on the lesions of maize plants in the field, which can be re-infected by airflow transmission. In addition to the degree of susceptibility of maize varieties, the epidemic of maize large spot disease is also closely related to the environmental conditions at that time. The temperature of 20-25 and the relative humidity of more than 90 are conducive to the development of diseases.

When the temperature is above 25 or below 15 and the relative humidity is less than 60 for a few days, the development of the disease is suppressed. In the spring maize area, the temperature is suitable from jointing to earing, and there are continuous rainy days, the disease develops rapidly and is prone to epidemic. Nitrogen fertilizer deficiency during booting and heading of maize is more serious.

Low-lying land, excessive density, and continuous cropping are prone to disease.

Corn Spot Disease occurs in various regions, and the first of corn Spot Disease is caused by Helminthospora convex. In general, the disease first appears in the bottom leaf and then expands upward.

Corn leaf blight is a common disease of corn cultivation in Northeast China. It has the characteristics of wide distribution, rapid development, heavy harm, difficult control and filial piety. Every year, the yield of corn will drop significantly, and even 50-60% or even no harvest.

So how to effectively prevent and control? Let's find out.

Symptoms of corn leaf spot.

Corn leaf spot, also known as leaf blight, stripe spot and leaf blight, mainly affects corn leaves, leaf sheaths and covered leaves. Leaf disease will appear as small water-gray spots, which then quickly spread to the sides along the veins to form large brown spots. In severe cases, the disease will continue, the leaves will turn yellow and wilt, and the seedlings will die, resulting in large radiation, reduced yield or even failure.

Conditions under which corn leaf spot occurs.

The occurrence of corn leaf spot is not only related to the degree of susceptibility of maize varieties, but also closely related to local climatic conditions. The temperature is 20-25 degrees and the relative humidity is greater than 90%. During the period from jointing to heading, the disease progresses rapidly and spreads easily.

The more severe the disease, the lower the nitrogen application rate from booting stage to heading stage, and the higher the density of low-lying land.

Prevention and control measures for corn leaf spot.

1. Screen out resistant varieties. At present, there are many varieties of maize seeds, and the disease resistance varies greatly among varieties.

2. Strengthen agricultural regulation and control. The base fertilizer should be mixed with organic biological fertilizer and boron, magnesium, zinc, silicon sulfate and other medium and trace elements, and the seedling stage 6-8 leaves should be sprayed with light carbon fertilizer to strengthen the plant and prevent diseases.

3. Take medicine for prevention. Selecting the appropriate agent for pre-disease and disease prevention is an effective measure to prevent and control corn leaf blight.

4. Prevent in advance. In mid-June, 250g of corn per plant, 400 500kg of water, and 2 sprays in 10 15 days can effectively control corn leaf blight.

5. The first stage of the disease. In the early stage of the disease, spraying once every 5 7 days, spraying twice in a row, 500 grams of corn fungus per hectare, and watering 500 600 kg can prevent and control corn leaf blight and make corn grow healthily.

The above is an introduction to corn leaf spot, in order to effectively ensure the yield and quality of corn, all kinds of pests and diseases must be strictly controlled, and corn leaf spot is no exception.

The temperature is 20 25 and the relative humidity is more than 90%, which is conducive to the development of diseases. The temperature is above 25 or below 15, the relative humidity is less than 60%, and the development of the disease is inhibited for several days. In the spring maize area, from the scion to the jointing stage, the temperature is suitable, and in case of continuous rainy days, the disease develops rapidly and is prone to large-scale epidemics.

The lack of nitrogen fertilizer at the flowering and first stages of maize is more serious. Low-lying land, high-density, and continuous planting are prone to excessive density of low-lying land, and continuous cropping is prone to disease.

<> high temperature, high humidity, low ground, and high density are prone to occur. From July to August, high temperature and humidity are conducive to pathogen infection. Corn spot blight is a common disease of maize, which mainly causes damage to maize leaves.

When the leaves are damaged by spot blight, they will cause oval-shaped patches on the leaves, which are mainly reddish-brown in color. Over time, the corn will gradually turn grayish-white in the center, light brown at the edges, expand into irregular lesions, and eventually lead to the death of local leaf spots. In severe cases, disease spots will appear on the entire leaf, and the whole leaf will die and fall off, resulting in a decrease in corn yield and quality.

The causative agent of corn spot blight overwinters in the soil and disease in the form of mycelium and conidia, and begins to spread the following year when the environment is suitable, becoming the main source of infection. At the same time, it can also lurk in the seeds, causing seedling damage after sowing. After the conidia absorb water, they come into contact with the colloid, producing a large number of conidia.

It is then spread through wind and rain, farming operations, etc. The infection begins in the stomata of the corn plant, and the pathogen produces conidia, leading to reinfection. Spot blight is most severe in environments with high humidity and low temperatures.

Do a detailed interpretation of the problem, I hope it will help you, if you have any questions, you can leave me a message in the comment area, you can comment with me more, if there is something wrong, you can also interact with me more, if you like the author, you can also follow me, your like is the biggest help to me, thank you.

For example, it often occurs during the rainy season, or often in a humid environment, or in the absence of fertilizer, or in the soil is deficient in nutrients, all of which are prone to spot blight.

For example, it often occurs in the dry season, or often in a humid environment, or in the absence of fertilizer, or in the absence of nutrients in the soil.

Soil permeability is not good, nutrients are relatively low, ventilation time is short, sunlight time is short, and lack of nutrients are prone to corn spot blight.

If the maize environment is lower than 15 degrees or higher than 25 degrees, spot blight is prone to occur. Corn fields are also prone to low humidity.

Corn spot blight is a common disease of maize. The initial lesions are oval, reddish-brown, then irregular in the center with grayish-white and light brown edges, resulting in localized leaf death. The two are often mixed together and are difficult to distinguish.

The conidia of corn belong to the class of semi-known fungi. The conidia of corn spores are oblate, born on both sides of the leaves, scattered or aggregated and buried, the mouth is slightly exposed, the wall is brown, charcoal, and the size is 69-135um.

<> conidia nearly cylindrical or cylindrical to needle-shaped, colorless or slightly greenish, straight or slightly curved, nearly truncated at base, slightly pointed at apex, diaphragm 1-4, 13-33. The size of the conidia is 90-210um. Conidia linear or whip-shaped, colorless and transparent, apex pointed, base obtusely rounded, slightly curved to curved, with 8 septums, 42-80 in size.

Corn leaf spot mainly affects leaves, and irregularly shaped lesions appear. Yellow streaks appear on the main lobe; The leaves are twisted, cracked, folded, and the tips are dry and shriveled; The plants are dwarf, haggard, the heart leaves stop growing, the root system is underdeveloped, and they are yellowish-brown; There are obvious yellow patches on the garlic balls, and after no moss or jointing, the garlic fruits become smaller and stiffer in severe cases. Corn leaf spot mainly affects leaves, and leaf atrophy occurs.

Corn leaf spot is divided into large leaf spot and small leaf spot. The disease mainly affects leaves, and in severe cases, it also affects leaf tips and bracts. Field diseases generally start at the lower leaves of the plant and gradually spread upwards.

At the beginning of the disease, it is a small water-stained light brown spot, and then expands to both sides along the leaf veins, showing a yellowish-brown long spindle-shaped or spindle-shaped large spot, 5 10 cm long and about lcm wide. Some lesions are larger, and in severe cases, the leaves are scorched. The main damage to the leaves is the yellowing of the leaves!

Atrophy. Do a detailed interpretation of the problem, I hope it will help you, if you have any questions, you can leave me a message in the comment area, you can comment with me more, if there is something wrong, you can also interact with me more, if you like the author, you can also follow me, your like is the biggest help to me, thank you.