Pre-Emergent Herbicide Guide

Crabgrass seeds will begin to germinate when the soil stays above 50° for 2 or 3 days in a row.

***PRO TIP*** When to apply pre-emergent herbicides. The first crabgrass that sprouts in the spring is usually next to sidewalks, driveways, and patios. These concrete slabs heat up in the sun and keep the nearby ground warm. Any seed that accumulates next to these slabs will sprout a little sooner than seeds in the rest of the lawn. Watch for those "early bird sprouts." When you see them, it is time to apply your preemergent herbicide.

Pre-Emergent Herbicide Active Ingredients

  • Pendimethalin

(Products: Pendulum Aqua CapPendulum 3.3 ECPendulum 2G) is a common crabgrass preemergent used on lawns. Although it is inexpensive, it has some drawbacks. It inhibits root growth in existing grasses, it may stain concrete, and it is relatively short-lived. A second application is often necessary, which can eliminate any cost-saving.

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  • Oryzalin

(Products: Surflan Pro, Surflan 4 Pro, Surflan ASSurflan T&OXL 2G) Similar to pendimethalin. It is inexpensive and effective but the concentrates can create orange stains on concrete if not washed off immediately after applying. Also, it may injure ornamental plants and shrubs so careful application is very important.

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  • Dithiopyr

(Products: Dimension 2 EWDimension Ultra 40 WPDithiopyr 2LBonide Crabgrass & Weed Preventer) has become a very popular choice for preemergent applications because it doesn't stain, and it doesn't cause damage to roots like oryzalin and pendimethalin. This is important when you overseed in the fall since there may be immature grass sprouts struggling to survive in the lawn. Like other preemergent products, dithiopyr stops crabgrass seeds from growing. What sets dithiopyr apart is that it also kills newly sprouted crabgrass shoots, as long as they have not gotten past the 2-3 leaf stage. This gives you more latitude in the timing of the application. Dithiopyr is the most forgiving preemergent herbicide available.

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  • Prodiamine

(Products: Barricade 65 WGResolute 65 WGProdiamine 65 WDG) is one of the least water-soluble herbicides, making it very long lasting in the soil. In fact, it is often applied in the fall to prevent crabgrass the following spring. You should not overseed within four months of applying prodiamine.

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  • Isoxaben

(Products: Gallery 75DFIsoxaben 75 WG) works only on broadleaf weeds, so it is not effective on crabgrass. It is a long lasting (8 month) preventer for broadleaf weeds though.

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