Thursday, March 13, 2008

Turfgrass - Tenacity Herbicide (mesotrione) Now Available

Mesotrione, the active ingredient in the new turf herbicide, Tenacity, has a wide range of activity on turf weeds and will give us a tool to control some of our difficult weeds. It received registration over the winter and is now available but only for use in golf courses and turf farms. A residential turf label is expected later in 2008. The following is some information on this herbicide.

Mesotrione the active ingredient in a new herbicide that is registered now for use in turf. Syngenta has named the herbicide Tenacity. Mesotrione is a pigment inhibitor type herbicide (turning weeds white) that will have many uses for weed control in cool season turf. It has excellent safety on tall fescue, perennial ryegrass, and Kentucky bluegrass.

With annual grass weeds, mesotrione is highly active against crabgrass both pre and post emergence, has shown the ability to control goosegrass at higher rates, and is active on annual bluegrass as a fall treatment pre and post emergence.

What is noteworthy is that mesotrione can suppress or control certain weedy perennial grass species including nimblewill, and creeping bentgrass in cool season turf. Another problem weed controlled by mesotrione is yellow nutsedge.

Mesotrione has activity against many broadleaf weeds such as chickweed, henbit, plantain, and oxalis. It has good activity on dandelion and fair activity on clover. However, when combined with triclopyr (Turflon), clover control is excellent.

Another feature of mesotrione is its safety on new turfgrass seedings. Research in New Jersey has shown that it can be used safely as a preemergence herbicide on new seedings. There is some risk of injury with early postemergence applications in the first 3 weeks of seedling growth, especially at higher rates so it is best used preemergence (after seeding but before emergence).

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

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