Use Prosecutor weed killer by spraying the product directly onto growing weeds until the plant's leaves are wet. Prosecutor kills most small weeds in one day and with a single application, while larger weeds, shrubs or trees can require multiple applications. Be careful not to get Prosecutor weed killer on desirable plants, such as flowers, grass or trees, as the product kills these plants, as well.
The active ingredient in Lesco's Prosecutor weed killer is glyphosate, the same chemical found in Monsanto's Roundup and other highly effective herbicides. Glyphosate kills plants by interfering with amino acid synthesis. After spraying on the leaves, glyphosate spreads rapidly throughout the entire plant, killing it very quickly. Glyphosate is only effective in actively growing plants, as dormant plants do not circulate the chemical internally.
Prosecutor and other glyphosate-based herbicides are relatively safe to use, as they are not especially toxic to humans or animals, and they break down rapidly. After plants sprayed with glyphosate die, the chemical travels into the upper layer of the soil. Unlike many other herbicides, glyphosate does not penetrate deep into the soil where it can cause problems later. Because microorganisms that live in the upper soil layers quickly break glyphosate down into harmless chemicals, plants can grow in areas treated with the chemical within a few weeks.