MSMA is an old herbicide that was sold for both the professional market for postemergence broadleaf and some grasses control in turf.  It was also available in the home use market primarily for crabgrass management.  However, because one component of the herbicide is arsenic the use of MSMA has been greatly restricted, primarily due to groundwater concerns.  It is currently only allowed for use in cotton and limited use on golf courses, sod farms and highway rights of way. 

• Golf courses:

–        One broadcast application allowed on newly constructed courses.

–        Application on existing courses limited to spot treatment (100 sq ft per spot), not to exceed 25% of the total course in one year.

• Sod farms:

–        Two broadcast applications allowed per crop.

–        25 foot buffer strip required for fields bordering permanent water bodies.

• Other MSMA Uses Not Allowed (sales stopped in 2009, usage stopped December 31, 2010).

–        Residential turf

–        Drainage ditch banks, railroad, pipeline, and utility rights of way, fence rows, storage yards and similar non-crop areas

–        Others (cemeteries, parks, etc.)

There are number of ways to manage most broadleaf weeds in turf but some grass and sedge weeds are notoriously difficult to control because it is often difficult to control grass weeds in a grass crop. Sedges are difficult to control regardless of the situation.  MSMA was popular because it controlled or suppressed crabgrass, dallisgrass, goosegrass, kikuyugrass, green kyllinga, and yellow nutsedge. 

On the other hand, a number of new herbicides have reached the market and are registered for use in California (see attached table).  The caveat is that many of these herbicides have the same mode of action and act on a single enzymatic pathway, specifically those in Group 2 (Table 1)).  Dependence on these herbicides has a high probability to cause the weed population to become resistant to those and similar herbicides.  Therefore, it is important to use these in rotation with herbicides in other groups and even more importantly, combine with or use other methods of management such as overseeding and managing irrigation and mower height to help provide sustainable weed management.  Additional information can be found at the Pest Management Guidelines for Turfgrass for professional turf managers (http://ipm.ucdavis.edu/PMG/selectnewpest.turfgrass.html) and the UC Guide for Healthy Turf (http://ipm.ucdavis.edu/TOOLS/TURF/) for home gardeners and managers of parks, school grounds, and other low-maintenance turf.

Table 1. Examples of replacements for MSMA and their mode of action group.

Dimension – dithiopyr (pyridine, Group 3)

Drive XLR8 – quinclorac (quinolinecarboxylic acid, Group 4 (26 for monocots))

Dismiss – sulfentrazone (aryl triazolinone, Group 14)

Tenacity – mesotrione (triketone, Group 27)

Sedgehammer – halosulfuron (sulfonylurea, Group 2)

Monument – trifloxysulfuron-sodium (sulfonylurea, Group 2) 

Revolver – foramsulfuron (sulfonylurea, Group 2)

Certainty – sulfosulfuron (sulfonylurea, Group 2)

Celsius - iodosulfuronmethyl-sodium and thiencarbazone-methyl (triazinylsulfonylurea, triazolone, Group 2)