technical bulletin

l Introduction
Tenacity™ is a selective, systemic herbicide developed by Syngenta for pre- and post-emergence grass and broadleaf weed
control in several cool- and warm-season turf species. It is currently registered for use on golf courses and sod farms in
most states.* Tenacity provides the flexibility to control weeds in established turfgrass stands or at seeding to enhance turf
establishment. The active ingredient, mesotrione, has a novel mode of action and is based on a naturally occurring compound
produced by the bottlebrush plant (Callistemon citrinis). Tenacity is a HPPD (p-hydroxyphenylpyruvate dioxygenase) inhibitor
that prevents 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 followed by necrosis and death of
the plant.
l Physical and chemical properties
l Chemical structure
The EPA has granted reduced-risk status for Tenacity due to its favorable environmental fate, environmental toxicity, and human
health profile when compared to many registered alternatives. It provides control of major turf weeds, including crabgrass,
goosegrass, bentgrass, nimblewill, clover, chickweed, dandelion, oxalis, speedwell, Canada thistle, plus many others (see table).
Product use rates range from 4 to 8 oz per acre. A repeat application in two to three weeks is necessary for control of most
weeds that are treated post-emergence. Tenacity herbicide can be used for weed control prior to or at seeding of certain turf
species to reduce weed competition at establishment. Tenacity will also control bentgrass contamination in Kentucky bluegrass
and perennial ryegrass turf and is compatible with a seeding program into treated areas to enhance conversion.
Grass Weeds (monocots) and Sedges Controlled
Tenacity is:
• A new turf herbicide with a novel mode of action based on a naturally produced compound from the
bottlebrush plant (Callistemon citrinis)
• Highly active at low use rates as a pre- and post-emergence herbicide
• Provides selective broad-spectrum dicot and monocot weed control in a number of turf species
Broadleaf Weeds (dicots) Controlled
• Absorbed by leaves, shoots, and roots and rapidly translocated in the xylem and phloem of susceptible plants
• Favorable environmental fate and environmental toxicity profile compared to many herbicides
• Can use at or prior to seeding of proposed labeled turfgrass species
• Low toxicity to wildlife and aquatic organisms and non-persistent in the environment
*Tenacity™ is not currently registered for use in all states. Please check with your state or local extension service prior to buying or using this product.
TECHNICAL BULLETIN
Call 1-866-SYNGENTA (796-4368) to contact the Syngenta Customer Center and learn more.
©2008 Syngenta. Syngenta Professional Products, Greensboro, NC 27419. Important: Always read and follow label instructions before buying or using any mentioned products. Syngenta Crop Protection, Inc.
warrants that its products conform to the chemical description set forth on the products’ labels. NO OTHER WARRANTIES, WHETHER EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND OF FITNESS
FOR A PARTICULAR PURPOSE, SHALL APPLY TO SYNGENTA PRODUCTS. Syngenta Crop Protection, Inc. neither assumes nor authorizes any representative or other person to assume for it any obligation or liability other
than such as is expressly set forth herein. UNDER NO CIRCUMSTANCES SHALL SYNGENTA CROP PROTECTION, INC. BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OR HANDLING
OF ITS PRODUCTS. No statements or recommendations contained herein are to be construed as inducements to infringe any relevant patent now or hereafter in existence. Barricade®, Tenacity™, and the Syngenta logo are
trademarks of a Syngenta Group Company.
1
Weed control with post-emergence applications requires a second application after two to three weeks.
Apply to young, actively growing weeds with a NIS-type surfactant.
2
For best post-emergence control, apply to less than four tiller crabgrass and goosegrass.
TR-SLT7328
www.syngentaprofessionalproducts.com
SCP-727-00003-C 04/08
l Site of action for Tenacity.
Tenacity inhibits the enzyme HPPD
(p-hydroxyphenylpyruvate dioxygenase)
blocking the formation of plastoquinone
and tocopherols resulting in a number of
biochemical reactions including carotenoid
synthesis inhibition and the bleaching of
new growth.
l Tenacity selectively controls bentgrass out of Kentucky bluegrass, perennial ryegrass, and tall fescue turf.
TM
TM
Bentgrass removal with three applications of Tenacity
80
l Tenacity controls weeds
when applied at seeding with
turf safety. (WA trial)
Spring seeding of Kentucky bluegrass.
Tenacity 4oz/A Three weeks apart
Untreated
% Bentgrass
60
40
Untreated check
Tenacity 8 oz/A
l Tenacity selectively controls
yellow nutsedge in a new seeding
of tall fescue. (MD trial)
20
0
0
2
4
6
8
10
>14
WAT
l Tenacity has pre- and post-emergence activity on crabgrass.
Tenacity can be applied in combination with Barricade® herbicide as a pre-emergence, in split applications for pre- and postemergence, or as a post-emergence for crabgrass control. Combined with Barricade, it can widen the window of application
by controlling any crabgrass that has germinated.
Data from five trials, 2005–2007, (IL, IN, VA, 2WA)
l Tenacity controls a number of key dicot weeds such as dandelion, white clover, and buckhorn plantain. (NY, IN)
Tenacity 6 oz/A
Untreated check
l Environmental safety
The toxicity of Tenacity to aquatic organisms is very low.
l Mammalian toxicological properties
Tenacity has low acute mammalian toxicity and is not mutagenic, teratogenic, neurotoxic, or a reproductive or
developmental toxicant.
l Turfgrass species
Tenacity has been tested both pre-emergence and post-emergence on these species and was found to be safe for turf under
trial conditions to both established and newly seeded turf.
l Control of crabgrass (PA trial)
• Comparison of tank mix to untreated check
• Clear control with 6 oz/A Tenacity
and 0.65 lbs ai/A Barricade
Tenacity 6 oz/A +
Barricade 0.65 lbs ai/A
Early post-emergence
Untreated check
Kentucky bluegrass
Centipedegrass
Tall fescue
Perennial ryegrass
Fine fescue
(creeping red, chewings, and hard)
St. Augustinegrass
(grown for sod)
Poa pratensis
Eremochloa ophiuroides
Festuca arundinacea
Lolium perenne
5–8 fl oz
5–8 fl oz
5–8 fl oz
5 fl oz
Festuca spp.
5 fl oz
Stenotaphrum secundatum
4 fl oz