Tenacity is the brand name of a weed control or weedkiller product manufactured by Syngenta. As the name suggests, Tenacity is very persistent in killing weeds. It has a great safety profile, a broad label, and does not impact beneficial cool season turf grass. A great safety profile is because the active ingredient, mesotrione, is based on a naturally occurring compound produced by the bottlebrush plant (Callistemon citrinus). Mesotrione inhibits photosynthesis in susceptible plant species. Tenacity is applied either as a liquid application sprayed over the turf and weeds or as a granule that is applied as part of a starter fertilizer when seeding. Either way it is absorbed by plants through the roots, shoots and leaves and distributed throughout the plant by both xylem and phloem translocation.
Tenacity in action. Image on left is bentgrass in turfgrass, image on right is after treatment with Tenacity showing the bleaching of the turf.
‘White means its working,’ has been a tagline for Tenacity because the material turns weeds and the surrounding grass white. This is a temporary bleaching effect that occurs because the material interrupts cholophyll production.
Tenacity herbicide can be used for pre- and post-emergence control of more than 46 broadleaf weed and grass species. In eastern Massachusetts we have bluegrass, ryegrass and fescue species of turf. Tenacity herbicide is used by Greenhow Lawn Care for control of sedge, crabgrass, and bentgrass in lawns. In our area, it is the most effective solution to bentgrass when applied properly.
The correct application for bent grass is to apply the material every two weeks starting in early August. August 1st, August 15th, and August 30th is a sample schedule with an aeration and overseeding performed right around the last application of Tenacity. This process should be repeated for subsequent years until the bentgrass is eradicated.