What post-emergence herbicide works well for corn and when is the right time to apply it?

Everyone uses post-emergence corn herbicides every year, and the application of post-emergence corn herbicides has a very big impact on subsequent crops. So what post-emergence corn herbicides are there? Which herbicide works well?

First of all, there are many corn herbicide formulas, such as nicosulfuron, mesotrione, 2,4-D butyl ester, fluroxypyr, dicamba, etc., but the commonly used ones are generally the first 2, namely nicosulfuron + mesotrione, and in actual spraying practice, atrazine (which has a certain soil-sealing effect) is generally also added, and together they form a compound agent. In this way, it can be clearly seen that there are 3 common formulas: atrazine · nicosulfuron, mesotrione · atrazine, and nicosulfuron · atrazine · mesotrione. Below, let's talk about the advantages and disadvantages of these 3 agents.

1. Atrazine + nicosulfuron

This formula has been used for a relatively long time. What is sold on the market is generally nicosulfuron with a 4% content, while atrazine has 2 types, 20% content and 30% content, with a total content of 24% or 34%. This formula can control most weeds in corn fields, such as crabgrass, amaranth, dayflower, barnyardgrass, etc., but its effect on reed is average.

The advantage is that it is cheap. If bought at retail, it is only 4-5 yuan per mu. The disadvantages are also obvious, with 2 points. First, it kills weeds slowly, and the effect is only seen after 20 days. Second, weeds have strong resistance to it, and in some areas, the weed control effect is average.

2. Mesotrione + atrazine

Common contents of this formula are 55% (5% mesotrione + 50% atrazine) or 53% (15% mesotrione + 38% atrazine). It can also control broadleaf weeds, grassy weeds and sedges in most corn fields, but its effect on the troublesome reed is also average.

The advantage of this formula is that it takes effect quickly. About 7 days after spraying, weed death or the beginning of weed death can basically be seen. It also has 2 disadvantages. First, the price is slightly more expensive. If bought at retail, the price is about 8-10 yuan per mu. Second, if the application technique is not in place, weeds are likely to rebound later.

3. Nicosulfuron + mesotrione + atrazine

This three-way compound agent has been relatively favored in recent years. Common contents are 28% (2.5% nicosulfuron + 5.5% mesotrione + 20% atrazine, or 3% nicosulfuron + 5% mesotrione + 20% atrazine). It combines the characteristics of nicosulfuron and mesotrione, and its weed control spectrum is more extensive. For common reed, at the 2-4 leaf stage, the control effect is also good. If it is larger, it still has a certain inhibitory effect, preventing it from continuing to grow. In terms of weed-killing speed, it can basically take effect in about one week.

However, it also has a disadvantage, namely that it is expensive. If bought at retail, it costs about 15-20 yuan per mu. Compared with nicosulfuron + atrazine, one mu's worth can treat 3 mu. Therefore, when using this agent, the cost budget issue must be considered.

The above 3 are the common post-emergence corn herbicides currently on the market, and they are also the ones everyone uses more. Because each person's situation is different, they can be selected according to specific circumstances. In addition, one more reminder: the herbicides mentioned above are all suitable for ordinary field feed corn, and are not suitable for sweet corn, waxy corn, or seed production fields, etc.

When should post-emergence corn herbicides be applied? How can they be applied safely?

1. Spraying time

Because post-emergence corn herbicides need an absorption process of 2-6 hours after spraying, whether the weed control effect is good or bad plays a very important role during this period. When spraying in the morning, noon, or afternoon during high temperature and dry weather, because the temperature is high, light is strong, and the spray liquid evaporates quickly, the spray liquid will evaporate shortly after spraying. Therefore, spraying should be chosen before 10 o'clock and after 15 o'clock. This not only achieves the effect, but people will not suffer heatstroke.

2. Spraying method

Let me tell everyone a method summarized from actual spraying practice. On the premise that the amount of pesticide is sufficient, the more water the better (of course this does not mean adding water without limit, relatively speaking). For example, if you buy a herbicide, the recommendation is 1 bottle, 1 tank of water, 1 mu, that is, mix with about 15 kg of water and spray it on one mu. But if you mix 20-25 kg of water and also spray it on one mu, the effect is somewhat better than 15 kg of water.

To put it more plainly, change 1 bottle, 1 tank of water, 1 mu into 1 bottle, 2 tanks of water, 1 mu. Friends who are interested can try it, but note that the spray amount must be uniform, and there must never be a situation where one patch gets more and another gets less.

3. Size of weeds

The best period for using post-emergence corn herbicides is the 3-5 leaf stage of corn. Why?

When spraying post-emergence corn herbicides, many farmers have a misunderstanding, thinking that the smaller the weeds, the smaller the resistance, and the easier the weeds are to kill. Actually, this is not the case, because if the weeds are too small, there is no area for the herbicide to adhere to, and the weed control effect is not ideal.

The best weed age is from the 2-leaf 1-heart stage to the 4-leaf 1-heart stage. At this time, the weeds have a certain area for the herbicide to adhere to, the weeds' resistance is not great, and the weed control effect is significant.

4. Corn varieties

Because most post-emergence corn herbicides now contain nicosulfuron, and some corn varieties are sensitive to this ingredient and are prone to herbicide damage, corn fields planted with varieties such as sweet corn, waxy corn, and the Denghai series cannot be sprayed, to prevent herbicide damage. For new corn varieties, please test first before promoting them.

5. Pesticide mixing issues

Within 7 days before and after spraying post-emergence herbicides, it is strictly forbidden to spray organophosphorus insecticides, otherwise herbicide damage is likely to occur. However, they can be mixed and sprayed with pyrethroid and carbamate insecticides. When spraying, try to avoid the heart leaf to prevent the spray liquid from pouring into the heart.

This year, Swedish fly and thrips occurred severely in some corn fields. To control these two small pests, imidacloprid or acetamiprid can be used to spray the heart leaf, but when spraying, do not mix and spray with post-emergence herbicides. Although imidacloprid or acetamiprid are not organophosphorus, because controlling these two small pests requires spraying the heart leaf, if mixed and used to spray the heart leaf, herbicide damage is likely to occur. They can be sprayed separately: spray the post-emergence herbicide in front, and immediately follow behind with imidacloprid or acetamiprid to spray the heart leaf.

Everyone must pay attention to the above 5 points when spraying post-emergence corn herbicides, to avoid herbicide damage and affect corn yield.

In addition, one more reminder: when spraying herbicides in summer, the weather is often high-temperature and dry, so under the condition of not affecting the pesticide effect, be sure to use more water to improve the weed control effect. And when spraying, be sure to pay attention to personal safety and take heatstroke prevention measures!