Difference between mode and site of action for herbicides

There's a difference!?

When we refer to the site of action, we are talking rightly of the mechanism, specifically, where the herbicide will act is the point of the plant metabolism that will be modified by the herbicide molecule. From that point can occur several chain reactions that will lead to the death of the plant, these reactions are part of the herbicide's mode of action. The herbicide's mode of action begins in the contact of the herbicide with the plant, as it penetrates the plant (absorption), how it moves (translocation) and how it reaches the site of action up to the visual symptoms and the death or control of the plant. In other words, the site of action is part of its mode of action of the herbicide.

⛔ No not do this⛔

Therefore, it is incorrect to speak in a rotation of the mode of action of herbicides, since they can have different modes of action and even have the same site of action, which is not advisable for weed management. The correct then is to rotate the site of action of the herbicides. The importance of make this rotation will be discussed in another post [coming soon...]

After so much rotation or not, let's exemplify everything to see if things fit together.

Let's go to our example 😅

Let's talk about group B(HRAC), 2(WSSA) SOA classification, and what are the herbicides in group B? Are ALS inhibitors, and how do ALS inhibitors generally work? After the application of the herbicide the formation of the amino acids (Valine, Leucine, and Isoleucine) are blocked, therefore does not occur the formation of proteins and this lack of proteins negatively affects the DNA Synthesis and cell division.

Relax we'll talk more about the modes of action of specific herbicides, but just ahead 😉

So, imagine that we use the herbicide Diclosulam in pre-emergence and we do not control very well the weeds presents in our area. Good, we still have other chances in the post-emergence of culture, so I tell you

"Friend, we have to use a herbicide that has a different mode of action."

And you choose the herbicide Nicosulfuron and amazing that It seems the choice of the herbicide is correct, but it is not the right choice.

Hãmm what...😵!?

If you chose the herbicide based on the phrase I said take a herbicide with different mode of action you are correct in your choice, Diclosulam is used in pre-emergence, while Nicosulfuron is used in post-emergence, that is, the mode of action already starts differently in the form of absorption where Diclosulam is absorbed mainly by the root, while the Nicosulfuron is mainly absorbed by the leaves of the weeds, and that is the obvious difference, they are more. But they possess the same site of action, both are ALS inhibitors, so the same infesting flora that "escaped" from the first application, will most likely also escape from this second application. This phrase may not be true depending on the plants that are present in the area, but with absolute certainty the rotation of the site of action is the best option, increasing the spectrum of plants that can be controlled and to avoid the pressure of Selection of resistant weeds, but this is for another post, we stay here in this post.