Pre-Emergent Control for Crabgrass

Recommended Herbicides

• Pre-emergent crabgrass control herbicides include benefin, pendimethalin, dithiopyr, prodiamine, oxadiazon and siduron, as noted by the Purdue Cooperative Extension. All chemicals are sold under different trade names. Keeping the crabgrass seed from germinating consistently over the year is the main strategy for crabgrass control.

Organic Pre-emergent Control

• Corn gluten is an organic crabgrass control obtained from the processing of corn meal. The use of corn gluten on lawns and other landscape areas reduces crabgrass by 86 percent in the first year and by 98 percent in the second year of growth, according to "The Ann Lovejoy Handbook of Northwest Gardening." Since it is also a rich source of nitrogen, 10-1-10, corn gluten also works as an effective weed and feed source.

Application Time

• The best time to apply pre-emergent herbicides is between early April and early May as this is the typical time for crabgrass seed germination. However, according to research by Purdue University, the products may also be used as early as the beginning of March. Avoid the use of any pre-emergent herbicide, except siduron, on newly-seeded lawns or areas that need to be seeded. The chemicals will affect the germination of grass seed as well, warns the University of Rhode Island Extension.

Application Suggestions

• Water the treated areas well after application. The germination rate of crabgrass seed varies by weather conditions. A good indication of when to use the chemicals is once you see forsythia start to bloom, suggests David Mellor in "Picture Perfect." Apply the herbicide evenly over the entire lawn area. If not applied uniformly, it will encourage the weed to move into non-treated areas. Do not seed treated areas for two to four months after herbicide use.