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By Brad Tipton
OSU Extension Educator
The best time to apply a spring pre-emergence herbicide to control crabgrass and other lawn weeds is right now. A pre-emergence herbicide kills weed seeds as they germinate and begin growing through the chemical barrier near the soil surface.
Once crabgrass or broadleaf weed leaves emerge above-ground, pre-emergence herbicides are useless in controlling these growing weeds. Furthermore, pre-emergence herbicide products must be watered-in with about an inch of rain or irrigation water to activate the herbicide.
Here is a listing of some of the commonly used pre-emergence herbicides. The trade names are listed first followed by the active ingredient in parenthesis.
Barricade (Prodiamine) is a granular herbicide that provides the longest weed control, but must be activated with at least one-half inch of water. The label will indicate that it is preferable to water the product in with 1 inch of water within 14 days following product application.
Surflan (Oryzalin) is a liquid product that provides a broad spectrum of weed control including broadleaf weeds, crabgrass and some reduction in sandburs. Incorporation with one-half inch of water needs to occur within 21 days following application.
Balan (Benefin) is typically an active ingredient in several products like XL-2G, Excel, Regalstar, Team 2G, and alone as Balan. These products are best applied in early March due to Benefin’s shorter time of herbicide activity than other compounds.
XL 2G (Benefin and Oryzalin) is obviously a combination of Balan and Surflan. Activation is necessary within the 21-day window following application and needs one-half inch of rain or irrigation.
Team (Benefin and Trifluralin) is another combo pre-emergence herbicide with Balan and Treflan. This product will photo-degrade quickly and needs to be watered in within a few hours after application.
Pendulum 2G (Pendimethalin) needs to be applied with care according to label directions and watered in soon after application. Products with Pendimethalin will tend to stain more than other chemicals.
Dimension G (Dithiopyr) is a little more expensive for crabgrass control than other materials previously discussed. However, it is the only chemical that has some limited post-emergence activity on young crabgrass that has just emerged.
The previous products mentioned are not all inclusive, but do contain the major active ingredients used for pre-emerge weed control in lawns. Drought has weakened many Bermuda grass lawns, and weeds will be even more problematic this year than they were in 2012.
Pre-emergence herbicides are cheaper and much easier to use than post-emergence weed control products. However, for pre-emergence products to be effective, application timing and proper activation are critical for successful weed control.