Post-emergence weed control in corn is crucial - what type of herbicide is more suitable?

Corn has now entered the late growth stage, and in just over a month the new corn should be on the market. At this point, post-emergence weed control in corn seems a bit late, but it does no harm to discuss it together here.

What is the best herbicide for post-emergence weed control in corn?

There are now many corn herbicides on the market, and the dazzling array of herbicides makes growers dizzy with choices. Overall, however, the more popular post-emergence corn herbicides on the market are nicosulfuron, nicosulfuron plus atrazine, mesotrione, topramezone, acetochlor, atrazine, and so on. But no matter how many herbicides there are, they still fall into just a few major categories: amides, triazines, sulfonylureas, and phenoxy carboxylic acids. Each herbicide can only be said to have its pros and cons, and none is perfect. When using them, you still have to consider your own field's corn conditions, weed conditions, and so on comprehensively.

Common corn herbicides

First, let us look at what types of main weeds are found in corn fields. The common weeds in corn fields fall mainly into three major categories: broadleaf weeds, grasses, and sedges. Common broadleaf weeds include purslane, black nightshade, and field bindweed; grasses include green foxtail and goosegrass; and the most common of the last category is purple nutsedge.

Moreover, in recent years purple nutsedge has shown an upward trend as a weed. This is especially true for summer corn, because the abundant rain and heat during the corn growing period make it very easy for weeds to run rampant. This also shows the importance of weed control at the corn seedling stage.

Here, let us first look together at where the advantages and disadvantages of various herbicides lie.

First are the amide herbicides. This type of herbicide is actually not suitable for use at the corn seedling stage, because this type of herbicide is generally applied as a soil treatment, playing a role in pre-emergence weed control. But at the seedling stage, the corn seedlings have already emerged and the weeds have already grown out, so using this type of herbicide at the seedling stage has very little effect. Common herbicides in this category include alachlor, acetochlor, and butachlor. They are more suitable for eliminating grass weeds in corn fields, but their effect on broadleaf weeds and sedges is not obvious.

The second category is triazine herbicides. One point similar to the amide herbicides mentioned above is that the application method of this type of herbicide is also soil-based, but this type of herbicide is mainly highly effective against broadleaf weeds. Common herbicides include cyanazine, atrazine, and so on.

The third category is sulfonylurea herbicides. It should be said that this type of herbicide is more suitable for weed control at the corn seedling stage, because its application method is more flexible, and it can be used both on soil and on stems and leaves. Its safety to corn is relatively higher. Common varieties include nicosulfuron, rimsulfuron, and so on. Here, taking the more commonly used nicosulfuron as an example, it is a systemic herbicide, and killing weeds requires a certain amount of time. Generally, about 20 days after use, weed death can be seen. It is effective against both grass weeds and broadleaf weeds.

The fourth category is phenoxy carboxylic acid herbicides. This type of herbicide, like sulfonylurea herbicides, is a systemic herbicide, with a broad weed-killing spectrum, and is relatively effective against broadleaf weeds and sedges. Common ones include 2,4-D butyl ester, MCPA, and so on.

In addition to the four common types of corn herbicides mentioned above, there is also the relatively common glyphosate. Glyphosate belongs to the organophosphorus herbicides, and glyphosate is a non-selective herbicide, so its killing power is relatively strong. Therefore, glyphosate is not used for weed control in corn, as it easily causes herbicide damage.

The herbicides mentioned above all belong to the single-agent category. There are currently many mixed herbicides on the market, and their weed control effect is also good, so they will not be described in detail here.

However, at present, the herbicide commonly used for weed control at the corn seedling stage is still mostly nicosulfuron, followed by mixed-formulation herbicides, such as nicosulfuron plus atrazine, mesotrione plus atrazine, and so on.

Choosing the time for corn weed control

Corn weed control can generally be carried out at three time points: one is pre-emergence soil-sealing weed control, one is seedling-stage weed control, commonly known as removing small weeds, and another is weed control in the middle and late growth stages of corn, which farmers often call removing large weeds. Among these three weed control methods, the most commonly used is post-emergence weed control at the corn seedling stage. That is, when the corn seedlings have grown to two to six leaves, and during this stage, when the corn is at the "three leaves and one heart" stage, it can be said to be the best time to use herbicides on corn, as the corn's herbicide resistance is stronger.

Finally, the above herbicides can only be used on ordinary corn. Sweet corn, waxy corn, and so on are not suitable for use, as herbicide damage easily occurs.

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