Crabgrass

Asked October 5, 2020, 8:05 PM EDT

How do i stop crabgrass

Newaygo County Michigan

1 Response

Good Morning,
One of the correlations for turf managers is when the forsythia (yellow bells) is blooming, a preemergent should be applied to prevent crabgrass. The reasoning behind this recommendation is crabgrass starts to germinate when soil temperatures reach 57 degrees F. Forsythia typically blooms about two weeks before soil temperatures are warm enough for crabgrass to begin to germinate. This gives homeowners time to apply a preemergent herbicide. Preemergent herbicides needs to be watered-in or rained on to be effective against crabgrass, so the two week window gives enough time for a rain shower to activate the herbicide for good crabgrass control. This system of watching for the forsythia bloom is better than just using a date on the calendar because, if the preemergent herbicide is applied too early, it will break down and crabgrass will become a problem in late spring. If the herbicide is applied too late, the crabgrass will not be controlled. The forsythia bloom helps get the timing of the preemergent application right.
There are a number that can be purchased and applied by homeowners. Look for products containing active ingredients like: benefin, benefin and trifluralin, bensulide, dithiopyr, indaziflam, metolachlor, oryzalin, pendimethalin, or prodiamine. Many of the products labeled for this have crabgrass somewhere in the brand name or trade name. They are often sold as Crabgrass Preventer. Most prevent other weeds also. Granular products are the most commonly available for homeowners. The two most common active ingredients available for homeowners are either pendimethalin or dithiopyr. They are not always found with the other chemicals but may be located near fertilizers or registers.

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