1. Malnutrition
When corn lacks nitrogen, phosphorus, potassium or copper, it may lead to short stature and slow growth of corn plants.
2. Toxicity to plants
When nicosulfuron is used to control weeds, it should be applied before the 4-leaf stage of corn and not later than the 5-leaf stage. Otherwise, single use or mixed use will cause phytotoxicity. The symptom is that the maize plant is short, but stout, with dark green leaves and hard heart leaves, and it is difficult to pull out the joints due to serious drug damage.
There are too many weeds in the field.
In the corn field with serious weeds, the corn plants are short, the root system is underdeveloped, the growth is poor, the leaves are yellowed, the ear becomes smaller, the empty grain rate increases, the grain weight decreases, and in severe cases, the seedlings wither and die.
4. Nematode diseases
There are two main mechanisms by which nematodes harm maize roots: one is mechanical injury; The second is chemical action, which destroys or kills root cells by secreting or injecting enzymes, reduces the ability of root system to absorb and transport water and nutrients, destroys the normal function of root system, stops the growth of root system, leads to poor plant growth, and reduces production with plant fading or other nutrient deficiency. After nematodes harm the root system of maize, it not only reduces the plant vitality and affects the growth, but also weakens the resistance to other diseases, forming necrotic spots or gall, deformation, dwarfing and yellowing.
5. Corn root rot
Root rot of maize can occur from seedling stage to ear stage, which mainly shows that hypocotyl and the whole root system gradually turn brown, soften and rot, the growth of root system is seriously hindered, plants are short, leaves turn yellow and seedlings die.
6. Maize dwarf mosaic disease
Maize dwarf mosaic disease can be susceptible in the whole growth period of maize, and it is seriously harmful at seedling stage. At seedling stage, elliptic chlorosis spots or stripes appear between veins at the base of heart leaves, which grow short and intermittent stripes along veins and gradually spread to the whole leaf, and mesophyll tissue turns green and yellow, forming obvious yellow-green stripe symptoms. The new leaves are particularly obvious, starting from the tip and edge of the leaves, purple stripes appear and finally dry up. Generally, the first chlorosis area of diseased leaves develops into an inverted figure along the leaf edge and leaf base, and the upper diseased leaves become mosaic when all leaves are unfolded. Plants susceptible to early and severe diseases are obviously dwarfed, and they cannot head or die early. After the seedlings with toxic seeds are unearthed, the leaves are light green or yellow-green, and gradually appear as a mosaic composed of a large number of dark green patches or spots. Sick seedlings are usually shorter than healthy seedlings.
7. Maize Rough Dwarf Disease
Rough dwarf disease can occur in the whole growth period of maize, and it is most likely to occur at seedling stage. The symptoms of the disease usually appear in the 5 ~ 6 leaf stage. The leaves of the diseased plant are dark green, hard and brittle, short and thick in width, thick and short in internodes, and the white and green heart leaves can't unfold normally, like Clivia, they can't unfold, even rot and die. Transparent dotted-line chlorotic stripes appeared on the venules on both sides of the main vein of the heart lobe. With the growth of the plant, clear waxy teardrop-like linear protrusions with different lengths can be seen on the veins on the back of the leaves, which are called vein protrusions. Internodes become thicker and shorter, obviously shorter. When the seriously ill plants are not heading or after heading, the male floral axis is obviously shortened, the male flowers are stunted, the fruit ear is small, the fruit ear is deformed, and there are no fruits or few seeds.