Simazine vs Atrazine

Both simazine and atrazine are herbicides, and both belong to the tirazene class of nitrogen-containing compounds. Crops are sprayed with either. Yet despite their similar names and chemistry, the two herbicides have some differences.

To provide a good idea of what distinguishes the two, this comparison will explain the herbicides’ main properties and uses as well as their differences and similarities. 

What is the difference between atrazine and simazine?

  • Targeted vs Untargeted

One main difference between simazine and atrazine is that the latter is a selective herbicide while the former is non-selective.

This means that atrazine kills a particular type of plant while simazine kills plants more indiscriminately. That is, atrazine is known to be more targeted for weeds specifically.

  • Chemical Differences

Simazine and atrazine have some chemical differences which result in certain differences in effects when they are used as herbicides. Such differences are relevant to crop growers. For instance, sorghum and corn crops are more sensitive to simazine than atrazine. For this reason, atrazine is more commonly used for corn and sorghum crops.

Atrazine is also an exclusively pre-emergent herbicide, which means that it can only be applied before weeds have surfaced. It cannot, like Simazine, kill weeds after they have emerged from the ground.

Finally, cattle and sheep are very sensitive to Simazine, which can make it dangerous to spray the product on animal farms.

For these reasons, atrazine is somewhat more popular than Simazine as an industrial herbicide.

  • Different Runoff Risks

Another significant difference between Simazine and Atrazine involves their environmental impacts. Studies have shown that due to differences in solubility, simazine is better in terms of preventing runoff. In other words, simazine is less likely than atrazine to wash away and contaminate other environments after it accumulates under a crop.

What Does Simazine Kill?

Since simazine has non-selective properties, it kills a broad variety of weed and grass species. It is known to control most annual broadleaf weeds such as Carpetweed and Russian Thistle. Simazine also eradicates the majority of annual grass weeds, including Crabgrass and Ryegrass.

Two notable factors determine how well simazine will prevent a weed outbreak in a given area. Those factors are:

-How much time has passed
  -simazine will stay active in the soil for 2-7 months
  -since there are different manufacturers of  this herbicide, the recommended period
   between application varies

-How well-irrigated the area is
-his is important because simazine must be absorbed by a weed’s roots to take effect

Uses Of Simazine

Simazine is primarily used as a herbicide on a variety of weeds and grasses in crops. There are many crops for which it is used, including those of fruits, berries, nuts, and vegetables. This means the herbicide, though lethal to many weeds, does not have the same effect on the types of plants humans need for food. By targeting only weed grasses, simazine can even be used for turf grass.


Both simazine and atrazine can be harmful in high enough concentrations and both are banned in the EU. They have been found in drinking water in North America, although whether they are being consumed in dangerously high concentrations is debated. For instance, in 2007 the EPA determined that the concentrations of atrazine in Americans’ drinking water was not dangerous.

Limited amounts of simazine are still used on crops in North America and parts of Asia, while atrazine is still used widely in the United States.

Both simazine and atrazine accumulate in water rather than food. Therefore eating from crops that were given either herbicide is not dangerous. Moreover, processing facilities continuously monitor the concentrations of triazine herbicides in drinking water.

The environmental harms caused by the widespread, long-term use of both simazine and atrazine have been significant. There is some evidence, for instance, that atrazine causes mutations in amphibians. In an attempt to reduce these types of environmental damages, many countries are tightening restrictions on the use of triazine herbicides.


There are alternatives to simazine as well as atrazine. In Europe, where both products are banned, a triazine called terbuthylazine is in use as a herbicide. Because it breaks down more rapidly, this chemical is safer than simazine and atrazine in terms of accumulation in water supplies.

Mesotrione is another simazine-alternative used in Europe. It is a derivative of a natural herbicide found in the Bottle Brush plant.

There have also been studies showing that corn crops do not have smaller yields when triazine herbicides aren’t in use compared to when they are.


Simazine is a herbicide that prevents the growth of most types of weed-grasses and broad-leafed weeds. Although it shares many uses with atrazine, the two also differ in some ways.

For instance, simazine is pre-emergent, meaning it is only used to prevent the growth of weeds that have not yet surfaced. Additionally, cattle and some crops are more sensitive to simazine than atrazine.

On the other hand, simazine seems to be better than atrazine at staying in the area of earth where it was first applied rather than running off and contaminating an adjacent environment.

Finally, there are alternatives to simazine and atrazine which may generate less harmful environmental impacts.

Now you should be well-informed on the uses and qualities of simazine herbicide, as well as how it differs from atrazine.

Also, read

How Much Atrazine per Gallon of Water

Will Atrazine Kill Bermuda Grass?

How Long does it Take for Atrazine to Work?


EPA Releases Draft Biological Evaluations for Atrazine, Simazine and Propazine – EPA

The Case for Banning Atrazine – The center of Biology diversity

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