What causes the leaves of corn to turn yellow and gradually dry up?

There are several main reasons why corn leaves turn yellow:

1, corn pests cause yellow corn seedlings.

The main pests in maize seedling stage are cotton bollworm, needle worm, aphid, armyworm, thrips, Swedish stem fly, cutworm, rice planthopper and so on. The nymphs and female adults of the planthopper concentrate in the stem base, roots and leaf sheaths near the surface of corn seedlings, absorbing juice, which leads to the yellowing and drying of the damaged leaf sheaths. Irrigation and spraying 500- 1000 times of 40% phoxim emulsifiable concentrate or 500- 1000 times of other systemic pesticides on the stem base or root of corn seedlings in time; (You can also rotate or stubble, because the tilapia mealybug only harms gramineous plants. ) Other pests can be treated with general high-efficiency and low-toxicity pesticides.

Due to the lack of water, corn seedlings turned yellow.

Drought in the late stage of maize leads to insufficient water and nutrition supply, which leads to yellowing of lower leaves; Under-watering before or after sowing, the seeds can't get enough water, which further affects the normal germination and emergence, and the digging time is too long, resulting in weak and yellow seedlings.

3. Maize seedlings turn yellow due to lack of nitrogen.

In the late stage of maize, the lower leaves first turn yellow, and gradually develop to the upper part, and in severe cases, the lower leaves die. However, the yellowing of its leaves began to change from the tip of the blade, showing an inverted "V" shape and gradually turning yellow.

4. Potassium deficiency in maize leads to the yellowing of maize seedlings.

In the process of yellowing, the blade starts from the tip of the blade, then the edge of the blade turns yellow and dry, and the whole blade dies in severe cases.

5. Flooding of maize caused maize seedlings to turn yellow.

When corn is flooded for a long time, generally more than 24 hours, the lower leaves will die quickly.

6, the harm of herbicides

Improper use of herbicides, a small number of farmers arbitrarily increase the amount of herbicides; Blindly mixing with other pesticides; The drug concentration is too high; Interoperability of sprayers; The influence of fake and inferior herbicides on subsequent crops will cause maize yellow seedlings.

7. Element deficiency

Corn is a kind of crop sensitive to zinc. When zinc is deficient, white seedlings will appear, which looks like yellow corn seedlings. Generally speaking, it is better to apply zinc fertilizer basically; In case of zinc deficiency in the growing period, zinc sulfate 1-2 kg can be used in seedling stage to mix fine soil 10- 15 kg per mu, and applied in strips or holes; Or use 0. 1% zinc sulfate solution (note: the concentration should not exceed 0.4%, so as not to cause fertilizer damage) to spray it twice at intervals of 7 days from seedling stage to jointing stage, and use 60 kilograms of fertilizer solution per mu.

8. illness

If the seedling stage encounters long-term low temperature and rainy weather, it will cause the occurrence and epidemic of corn seedling blight. Most of the diseases in seedling stage began in the second and third leaf stage, and the leaves of diseased seedlings turned yellow and dry, and the edges were scorched, and gradually turned yellow and dry from bottom to top; Less root hairs and underdeveloped brown roots lead to weak seedlings of yellow seedlings. Pay attention to spraying hymexazol+foliar fertilizer at the beginning of the disease.

9. Sow too deep

Too shallow sowing is not easy to emerge, but too deep sowing will lead to weak and yellow seedlings, and the sowing depth should be controlled at 3-5 cm; At the same time of sowing, applying a certain amount of seed fertilizer can promote seedling growth. For example, applying 3 kilograms of diammonium phosphate per mu during sowing can effectively prevent maize from yellowing at seedling stage.

10, seedling thinning is not timely.

After the emergence of maize, seedlings should be planted at 3-4 leaves, and seedlings should be fixed at 6-7 leaves to avoid squeezing seedlings to compete for fertilizer, water and glory, forming weak seedlings, diseased seedlings and yellow seedlings; The number of seedlings per mu should be flexibly mastered according to different varieties, and seedlings should be fixed according to the required density of cultivated varieties.