Preemergent Crabgrass Products

Recommended Herbicides

• Preemergent herbicides are applied to lawns prior to the growth of crabgrass. These chemicals retard the germination of weed seeds and keep the weeds from emerging. Recommended preemergent herbicides include benefin, oxadiazon, dithiopyr, prodiamine, pendimethalin and a combination of benefin and trifluralin, as listed by the Purdue Cooperative Extension. All chemicals are sold under different trade names. Corn gluten is recommended as an organic crabgrass control strategy.

Application Time

• The best time to apply preemergent herbicides is during early spring, prior to seed germination. Herbicides that are applied as early as March 1 are still highly effective in controlling weed growth all through the season. Use herbicides when temperatures are below 85 degrees F and preferably on clear days. Low atmospheric humidity at the time of application helps to increase the efficacy of chemicals.

Application Tips

• Water the treated area well after chemical application. Do not use preemergent herbicides on newly seeded lawns or new seedlings, since the chemicals will impede the germination of grass seed as well. Preemergent crabgrass control products containing siduron are the safest ones for newly seeded grass, as these do not affect grass seeds, suggests the University of Rhode Island Extension.

Corn Gluten Use

• Corn gluten is a nontoxic by product obtained from the wet milling of corn. The product is high in protein and is also used as part of animal feed mixes. The high protein amount in corn gluten keeps a wide number of weed seeds, including crabgrass, from germinating in spring. Use 10 to 20 lbs. of powdered corn gluten meal per 1,000 square feet of lawns, recommends Mike McGrath in "Mike McGrath's Book of Compost." Spread the product evenly on grass and water in well.