Mesotrione.
Inspired by nature. And inspiring golf course superintendents when it comes to weed control.

History of mesotrione.

The discovery of mesotrione began when, in 1977, a Syngenta scientist noticed that very few weeds were growing under a bottlebrush plant (Callistemon citrinus) in his garden. His natural curiosity took hold and after analyzing a soil sample, he discovered that the plant was secreting a substance known as leptospermone, a natural herbicide that suppresses the development of other plants.

Mesotrione is created.

After the 1977 discovery, Syngenta scientists went to work to mimic the natural herbicides (allelochemicals) secreted by the Callistemon plant (bottlebrush plant).
And mesotrione, the active ingredient in Tenacity herbicide, was created.

Mesotrione mode of action.

Mesotrione works by inhibiting HPPD (p-Hydroxyphenylpyruvate dioxygenase), an essential enzyme in the biosynthesis of carotenoids. Carotenoids protect the chlorophyll, the pigments in plants responsible for photosynthesis, from excess light energy.   

Without carotenoids, light energy destroys the chlorophyll, causing new growth to turn white and disrupting cell membranes, resulting in necrosis and death of susceptible plants.

Chart of Action

Mesotrione goes to work.

After application, mesotrione, found in Tenacity®, is absorbed by leaves and roots and rapidly translocated in the xylem and phloem of susceptible plants. In newly germinated weeds, Tenacity is absorbed through roots and shoots and therefore the plants fail to emerge or die shortly thereafter.

Golf course grasses like Kentucky bluegrass, perennial ryegrass and fescue are able to tolerate Tenacity by rapidly breaking down mesotrione into inactive compounds.

Chemical Structure

Environmental and mammalian safety of Tenacity.

The EPA has granted reduced-risk status for Tenacity in turf due to its favorable environmental profile, environmental toxicity, and human health profile when compared to many registered alternatives.


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