Doing what other herbicides can't with Tenacity

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

Tenacity® herbicide is a systemic herbicide for pre- and post-emergence control of grass and broadleaf weeds 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 works by inhibiting the synthesis 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.

Want to trial Tenacity on your course? Try the new easy squeeze-and-pour 8-oz. bottle.

At seeding

With Tenacity herbicide, you can control weeds at the same time as you seed. Most herbicide products remove weeds from established turf, but Tenacity can also be used to prevent weeds from emerging in newly seeded or overseeded turf. When grass seed has a chance to grow without weed competition, root establishment is stronger, resulting in a healthier, denser turf stand.

It may be applied to labeled turfgrasses anytime up to, during and after seeding, but prior to emergence. Tenacity is one of the few herbicides that controls weeds during the seeding process and provides pre-emergence and some post-emergence control of many weeds. View the Tenacity and Hydroseeding Information Sheet to learn more.

Tank-mix options

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 to clean up summer annuals and perennial weeds such crabgrass, clover, dandelion and oxalis. Tenacity tank-mixed with a dicot herbicide, such as triclopyr or dicamba, can enhance post-emergence control of crabgrass and dicot weeds.

Trial source: North Carolina, 2008

Removing bentgrass

Certain grasses like bentgrass (Agrostis spp.), nimblewill (Muhlenbergia spp.) and windmillgrass (Chloris spp.) are sensitive to Tenacity. Multiple applications can selectively remove these grasses from Kentucky bluegrass, tall fescue and perennial ryegrass. Coupled with a re-seeding program, turf areas can be converted to the desirable turf species.

It is recommended to apply Tenacity at 4-5 oz./A on a two- to three-week interval for three applications. Seeding can occur after the second application of Tenacity. Depending on location, applications of Tenacity starting in August or early September will best coincide with a re-seeding program for optimum turf conversion.

Below is a summary of Tenacity trials from across the U.S. over several years.

Trial sources: Illinois, Indiana, Iowa, South Carolina, Virginia and Washington, 2005-2007.

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

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