Featured Article | GreenCast | Syngenta

Synergizing cool-season weed control

By Dean Mosdell, Ph.D, technical services manager, Syngenta

Tenacity® herbicide is a systemic herbicide for pre- and post-emergence grass and broadleaf weed control in several cool and warm-season turf species. The active ingredient, mesotrione, is based on a naturally occurring compound produced by the bottlebrush plant (Callistemon citrinus). Tenacity is a HPPD (p-hydroxyphenylpyruvate-dioxygenase) inhibitor that prevents the formation of carotenoids in susceptible plant species. Without carotenoids, light energy and by-products of photosynthesis destroy chlorophyll and cell membranes, resulting in bleaching of leaves and plant death.

Tenacity is registered by the EPA under its Reduced Risk Program.* It provides control of major turf weeds including crabgrass, goosegrass, lovegrass, chickweed, dandelion, oxalis, speedwell, Canada thistle and many others (see product label). Product use rates range from 5-8 oz./A. A repeat application in two to three weeks may be necessary for control of weeds. Tenacity also controls bentgrass and nimblewill contaminations in Kentucky bluegrass and perennial ryegrass turf, and it is compatible with a seeding program into treated areas to enhance conversion.

One of the unique features of Tenacity is its ability to synergize weed control when tank-mixed with other active ingredients. Late spring and early summer are times when lawn care operators can clean up summer annuals and perennial weeds such crabgrass, clover, dandelion and oxalis. Tenacity tank-mixed with a post-emergence herbicide, such as triclopyr (TE) or dicamba, can enhance post-emergence control of crabgrass and dicot weeds (see chart below).

North Carolina, 2008

Performance assessments are based upon results or analysis of public information, field observations and/or internal Syngenta evaluations. Trials reflect treatment rates commonly recommended in the marketplace.


Tenacity can also be used at seeding to reduce weed competition and establish a lawn faster. When applied just prior to or at seeding of tall fescue, Kentucky bluegrass and perennial ryegrass, Tenacity will control crabgrass, purslane and carpetgrass (among other weeds) that seem to germinate at turf renovation. Tenacity can also be added to the hydro-seeding tank for seeding large areas.

A new seeding of a Kentucky bluegrass and perennial ryegrass blend, 2007.

Order a free customizable Tenacity brochure for homeownersTenacity brochure
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Syngenta offers a free brochure you can give to homeowners explaining how Tenacity controls lawn weeds. You can also customize the brochure with your company’s contact information. To order, visit GrowWithSyngenta.com.


For more information about Tenacity, contact your local Syngenta territory manager.

*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. Tenacity qualifies under one or more of the above criteria.

All photos are either the property of Syngenta or are used with permission.

©2020 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. Tenacity® and the Syngenta logo are trademarks of a Syngenta Group Company.


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