Mesotrione is a herbicide currently being evaluated for use in turfgrass. Many turfgrass managers have indicated concerns about the whitening, or antichromatic response of plants caused by mesotrione. Previous research at Virginia Tech evaluating all combinations of mesotrione, triclopyr, and fenoxaprop-P for common bermudagrass control resulted in plots treated with combinations of mesotrione and triclopyr had higher turf color than plots treated with mesotrione alone. Therefore, we speculate that triclopyr is an effective tank-mix partner for reducing antichromatic effects of mesotrione and improving efficacy towards perennial broadleaf weeds. Our objective is to evaluate mesotrione plus triclopyr for effects on turfgrass and weed color and weed control.

Studies were conducted at two locations and used a 2 by 4 factorial treatment arrangement. The first factor was single or sequential treatment and the second factor was the following herbicide treatment combinations: mesotrione at 0.125 lb ai/A, triclopyr at 1 lb ai/A, mesotrione plus triclopyr, and an industry standard for broadleaf weeds, SpeedZoneŽ at 4 pt/A. Fenoxaprop-P at 0.12 lb ai/A applied twice and a nontreated check were included as comparison treatments. Sequential applications were made at 3-week intervals. Plots were evaluated for turf color and weed control.

Tank-mixing mesotrione and triclopyr improves turf color compared to mesotrione alone. Nimblewill control 60 DAT was equivalent between sequential applications of mesotrione alone and mesotrione plus triclopyr while no other treatment controlled nimblewill. Tank mixing mesotrione and triclopyr with one application improved ground ivy, broadleaf plantain, and white clover control. The combination of mesotrione and triclopyr both reduces the antichromatic response of susceptible species and adds control of perennial broadleaf weeds that mesotrione alone does not control. Ongoing research is evaluating mesotrione plus triclopyr compared to each product alone for injury to Kentucky bluegrass, perennial ryegrass, bermudagrass, tall fescue, and fine fescue.