Crabgrass

(More lawn weeds)  (Control Options)  

Large crabgrass
Digitaria sanguinalis 

Lifecycle

Summer annual.

Growth habit

Grows up to 2 ft. tall; decumbent growth habit; swollen nodes. may root at nodes. Dies after the first frost in the fall.

Reproduction 

By seed. Seeds germinate from spring through late summer.

Conditions that favor growth

Mowing the lawn too short. Thin turf with bare spots.

Mowed crabgass

Management

Cultural control: Maintain healthy, dense turf that can compete and prevent weed establishment. Proper lawn mowing. 
Mechanical control: Hand pulling or using an appropriate weeding tool are the primary means of mechanical weed control in lawns. This is a viable option at the beginning of an infestation and on young weeds. Hand pulling when the soil is moist makes the task easier. Weeds with tap roots like dandelions or have a basal rosette (leaves clustered close to the ground) like plantain are easier to pull than weeds such as Bermudagrass (wiregrass) or creeping Charlie (ground ivy) that spread with stolons or creeping stems that root along the ground.
General chemical control: (lawns) A granular (apply with a spreader), selective, preemergent herbicide. There are numerous products on the market. Look for a preemergent without nitrogen fertilizer. Active ingredients include: bensulide, dithiopyr (offers postemergent control on young crabgrass seedlings), pendimethalin, prodiamine, and siduron (can be applied when sowing grass seed). 

A postemergent, selective herbicide that contains: Common Name: Quinclorac; Trade Name: Drive; others, can be combined with other active ingredients, Common Name: Fenoxaprop-p-ethyl;Trade Name: Acclaim Extra, others. Controls young weeds only. 

Rainfall or irrigation is required to dissolve the herbicide, which is then absorbed into the upper portion of the soil and forms a barrier which kills weed seedlings. Preemergent grass herbicides have residual activity that lasts for several weeks after application. High temperatures and rainfall will decrease the length of time they remain at sufficient concentration to be effective.

Tips for application:

• If planning soil disturbance, such as aeration, do it before application.
• Apply prior to crabgrass germination which begins when soil temperatures are above 55° to 60°F for 7 to10 days (during and shortly after, forsythia bloom is a rough, but not consistently reliable, guide for application timing). 
• Water after application, according to label.
• A second application may be possible, usually 6-8 weeks later (see label).
• Consult label for specific waiting period between application and overseeding.
• Corn Gluten for crabgrass control.

Organic control

For a glossary of herbicide terms and additional information see: control options  

Publication: (PDF) TT43-Herbicides for Crabgrass and Goosegrass Control in Turf