Six Major Taboos for Applying Post-Emergence Herbicides to Corn, a Must-Read for Anyone Growing Corn

Corn during the growing season, because there is more rain, weeds occur widely in the fields, so farmers all choose to spray herbicides. However, if a herbicide is applied improperly, it will cause herbicide damage and affect the growth of corn. To increase corn yields, first learn what precautions there are for applying post-emergence herbicides to corn. Only by taking preventive measures can you lay a good foundation for high corn yields.

Let us take you through the precautions for using post-emergence herbicides on corn.

1. When applying herbicide in a corn field, do this: "distinguish the variety clearly, do not use chemicals blindly."

Because most post-emergence corn herbicides now contain nicosulfuron, some corn varieties are sensitive to this ingredient and are prone to herbicide damage. Some products state that they are prohibited for use on corn inbred lines, sweet corn, waxy corn, Denghai series and other varieties. Therefore: post-emergence herbicides cannot be used on just any variety. You should read all the product instructions in detail; use them if they can be used, and do not use them if they should not be used, to prevent herbicide damage to corn seedlings.

2. When mixing the chemical, do this: "dilute twice, do not mix water and chemical directly," especially for powder-form chemicals.

Two-stage dilution is just like a cook making flour porridge. After choosing a certain amount of water, first mix a small amount of water evenly with the chemical, then add the remaining water, stir evenly, and spray. This avoids uneven mixing of water and chemical, which causes the "patchy field" weed control effect in which weeds die where the chemical was sprayed and continue growing where only water was sprayed.

3. When spraying, do this: "spray low, do not spray high."

The "low and high" mentioned here refer to low and high temperatures. That is, spray before 9 a.m. and after 4 p.m., when the temperature is lower during the day. Do not spray in the morning, at noon, or in the afternoon when the temperature is high and the weather is dry, because this limits the amount of herbicide that enters the weeds and makes the absorbed amount insufficient, affecting the weed control effect. At the same time, spraying at high temperatures also makes corn seedlings prone to herbicide damage.

4. When controlling weeds, do this: "spray small weeds, do not spray old ones." Seize the period from the two-leaf-one-heart stage to the four-leaf-one-heart stage of the weeds.

Spray during the favorable period when the weeds have a certain area to receive the chemical and have low resistance. Do not wait until the weeds have grown taller than 10 cm and look uniformly green before spraying. In hot and dry years, although the weeds are short, because they have grown for a long time, their root systems are well developed, forming grayish-white-leafed "small old weeds." You should increase the amount of spray solution, using no less than 40 kg of spray solution per mu, and spray the entire weed plant thoroughly and evenly. Never be stingy with water but stingy with chemical, otherwise you will not achieve a thorough weed control effect.

5. When controlling weeds and insects at the same time, do this: "mix with pyrethroid pesticides, and never mix with organophosphorus pesticides."

If insect pests occur in the corn field at the seedling stage, in order to save labor and time, when spraying post-emergence herbicides, weed control and insect control can be carried out at the same time. However, the pesticides mixed in should be pyrethroid and carbamate insecticides. When spraying, be careful to avoid the heart leaf as much as possible to prevent the solution from pouring into the heart. In years when Swedish fly or thrips occur severely, although herbicides can be mixed with imidacloprid or acetamiprid, controlling these two small insects requires spraying the heart leaf. If mixed with herbicides and sprayed into the heart leaf for insect control, corn seedlings are prone to herbicide damage. Therefore, spray the herbicide first and then spray imidacloprid or acetamiprid to avoid herbicide damage to corn seedlings. Within one week before and after spraying post-emergence herbicides, it is strictly forbidden to spray organophosphorus insecticides, otherwise corn seedlings will suffer herbicide damage.

6. When applying chemicals after the five-leaf stage of corn seedlings, do this: "spray in a targeted direction, do not spray the whole field."

The 2- to 5-leaf stage of corn is the best time to spray for post-emergence weed control. If the best period is missed and weed control is necessary, spray in a targeted direction along the rows and do not spray the whole field, so as to avoid herbicide damage. Otherwise, in mild cases the corn heart leaves turn yellow, and in severe cases the leaves turn white and the whole plant stops growing.