Lawn care professionals have used MSMA (Monosodium methanearsonate) since the 1960s to manage weeds such as crabgrass, goosegrass and nutsedge in warm-season turf. But the Environmental Protection Agency (EPA) ruled to discontinue sales at the end of last year.
Existing stocks of MSMA can legally be used for weed control on residential, commercial and sports field turf until they are exhausted, provided that these uses comply with the EPA-approved product label until December 31, 2013. But in the meantime, turf managers need to be considering new options for control of tough weeds in warm-season turf.
Crabgrass Control. Research conducted at the University of Tennessee evaluated post-emergence smooth crabgrass control with Drive XLR8, Solitare and Q4 herbicides at various stages of smooth crabgrass growth in 2010.
All treatments at the 1-4 leaf stage provided greater than 90% smooth crabgrass control at 40 days after treatment. At the 1-2 tiller stage, all treatments provided greater than 88% smooth crabgrass control for 28 days after application. At the 3-5 tiller stage, smooth crabgrass control with the 1 lb ai/A rate of Solitare exceeded 80% for 28 days while all other treatments controlled smooth crabgrass greater than 50%.
Purple Nutsedge Control. Several new herbicides have recently been labeled for effective post-emergence control of purple nutsedge in warm-season turfgrass species. Research conducted at the Texas Tech University in 2010 determined that Certainty and Dismiss South herbicides exhibited excellent purple nutsedge control (92% to 93%) 10 weeks after treatment when used at labeled rates.
Goosegrass Control. Pre-emergence herbicides are the best option for goosegrass control, says Dr. Jim Brosnan, of the University of Tennessee. But several post-emergence options are available. Illoxan is effective in bermudagrass, but it is not registered for use in all states, especially northern states. Revolver is another good option in bermudagrass. Dismiss herbicide provides goosegrass control to newly germinated goosegrass plants prior to tillering, and Tenacity provides post-emergence control on 3-tiller or smaller goosegrass.
Research is continually evaluating strategies to help soften the blow of losing MSMA as an option for control of key turfgrass weeds.