Atrazine is a general-purpose herbicide that works as both a pre- and post-emergent. This means it will kill existing weeds and those that have yet to spring up from the ground. However, you may want to think twice before using atrazine on your lawn.
Farmers regularly atrazine because it kills off grassy weeds. It is also deadly to grasses such as fescue grass and bahia grass. The rate of kill will vary with the type of grass, but atrazine has about a 75 percent success ratio when killing fescue.
Atrazine will kill unwanted annual grasses and broadleaf weeds. The herbicide needs rainfall for it to be effective, so do not apply it during a drought.
Atrazine is it is toxic to humans. The herbicide washes off the grass and contaminates water supplies, according to "Debating How Much Weed Killer is Safe in Your Water Glass," published in the Aug. 22, 2009 edition of "The New York Times." If ingested it can cause issues such as birth defects and menstrual problems in women.