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Syngenta Tenacity® Herbicide

Q         What is Tenacity?
Tenacity® herbicide is a new tool for lawn care operators for pre- and post-emergence weed control on cool-season turfgrasses such as tall fescue perennial ryegrass and Kentucky bluegrass.

Granted reduced-risk status by the U.S. Environmental Protection Agency (EPA), Tenacity (mesotrione on turf) can be used at seeding, including bare-ground seeding, or selective renovations and overseeding. It keeps weeds from germinating and allows new grass to flourish.

Q         What does it mean when the EPA says that Tenacity was granted Reduced Risk status? How did Tenacity earn this status?

A         The active ingredient in Tenacity, mesotrione, has been granted Reduced Risk status by the EPA for turf use.  It has favorable ecotoxicity and human health profiles, compared to many registered herbicides, which result in a reduction in the herbicide load on the environment.  Its mode of action is novel among turf herbicides, and it fits well into IPM and resistance management strategies.*

*A Reduced Risk pesticide use is defined as one which may reasonably be expected to accomplish one or more of the following: (1) reduces pesticide risks to human health; (2) reduces pesticide risks to non-target organisms; (3) reduces the potential for contamination of valued, environmental resources, or (4) broadens adoption of IPM or makes it more effective.  Mesotrione qualifies under one or more of the above criteria.

Q         How does Tenacity work? What is the mode of action?

A         Tenacity with a group 27 mode of action inhibits a plant enzyme called HPPD that is essential to photosynthesis and prevents formation of carotenoids in susceptible plant species. Without carotenoids, light energy and by-products of photosynthesis will destroy chlorophyll and cell membranes. This results in bleaching of leaves, followed by necrosis and death of the plant.

Q         How was Tenacity herbicide discovered?

A          A Syngenta scientist in California observed that there were fewer weeds growing under his bottlebrush (Callistemon citrinus) plant, far fewer than can be explained by shading alone. He concluded that the plant must be producing allelochemicals to suppress weed competition. Syngenta synthesized mesotrione, based on the allelochemicals produced by the bottlebrush plant.

Q         How quickly does Tenacity work?

A         Once absorbed, Tenacity quickly translocates throughout the plant. Weeds stop competing with the desirable turf soon after application, as photosynthesis is disrupted. Death of the unwanted plant usually occurs within two or three weeks.

Q         What weeds does Tenacity control?          

A         Mesotrione, the active ingredient in Tenacity, controls 46 dicot and monocot broadleaf, sedge weeds and grasses, including nimblewill, crabgrass, bentgrass, ground ivy, yellow foxtail and yellow nutsedge.                                                           

Q         Lawn care operators and their customers may see some bleaching or “whitening” of weeds after an application of Tenacity. Is that normal?

A         Yes — it means that Tenacity is working. Some degree of turf bleaching is to be expected when using the product, since its mode of action inhibits the enzyme that is essential to photosynthesis in susceptible weed species. This results in bleaching of unwanted weeds, followed by necrosis and death of the plant. Occasionally, white tips can also be seen on desirable grasses following treatment. This is a temporary symptom, as the tips will be removed during subsequent mowings.

Q         Why is Tenacity different than other turf herbicides currently used by lawn care operators?

A         Tenacity lets lawn care operators do things for their customers they haven’t been able to do before. It provides cost-effective pre- and post-emergence control over a wide range of weeds and undesired grasses — including nimblewill and bentgrass. Additionally, it provides an outstanding up-sell opportunity for selective renovations and overseeding of established turf.  Not only does Tenacity drive incremental revenue, but it helps reduce profit-robbing customer call-backs. There simply is no other herbicide available today that does all that.

Q         On which turf species can Tenacity be used?

A         Tenacity can be applied to many of the most common turf types such as Kentucky bluegrass, perennial ryegrass, tall fescue, fine fescue, centipedegrass and buffalograss.  Lower use rates are recommended for perennial ryegrass and fine fescue.    

Tenacity may be used at and before seeding on Kentucky bluegrass, tall fescue, perennial ryegrass, and centipedegrass. Application at seeding can also be made to seed blends of fine fescue if the fine fescue is less than 20% of the seed mixture.      

Q         Can Tenacity be tank mixed with other herbicides?

A         Yes it can. Tenacity can be tank-mixed with Barricade®, Princep® Liquid, Pennant Magnum®, dicamba, carfentrazone, triclorpyr, atrazine, bentazon and several three-way phenoxy herbicides. Combinations can help professional lawn care operators broaden their weed control capabilities. See label for specific rates on tank-mixes.

Detailed information about Tenacity can be found at: www.TenacityHerbicide.com

Q         How rainfast is Tenacity?

A         Tenacity is rainfast one hour after application.

Q         How will Tenacity be packaged?

A         For convenience and ease-of-use, Tenacity will be available in an eight-ounce bottle.  This pack size was designed to fit the needs of lawn care professionals – the price per container is reasonable and one container can spot-treat numerous lawns.  

Q         What is the anticipated sell date and ship date for Tenacity?

A         Tenacity in an 8 ounce bottle will be available April 1, 2011 and can be purchased by lawn care companies through authorized Syngenta agents and retailers.


As with all pesticides, it is important to read and follow label instructions when using Tenacity.

Syngenta is one of the world's leading companies with more than 26,000 employees in more than 90 countries and is dedicated to one purpose: Bringing plant potential to life. Through world-class science, global reach and commitment, Syngenta assists customers increase crop productivity, protect the environment and improve health and quality of life. For more information about Syngenta, please go to www.syngenta.com.

©2011 Syngenta Crop Protection, LLC., 410 Swing Road, Greensboro, NC 27409. Important: Always read and follow label instructions before buying or using Syngenta products. The label contains important conditions of sale, including limitations of remedy and warranty. Tenacity is not currently registered for use or sale in all states. Please check with your state or local extension service prior to buying or using  this product. Barricade®, Pennant Magnum®, Princep®, Tenacity® and the Syngenta logo are trademarks of a Syngenta Group Company.

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