How do I control crabgrass in my lawn?

FAQ
Question: 

How do I control crabgrass in my lawn?

Answer: 

The best way to prevent crabgrass infestations in lawns is to maintain a thick, healthy lawn through proper mowing, irrigation, and fertilization.  Crabgrass will have a difficult time germinating and surviving in a dense stand of turfgrass.  Gardeners who have had crabgrass problems in recent years should apply a preemergence herbicide in spring.  Preemergence herbicides must be applied before the crabgrass seeds germinate and are not effective on emerged weeds.  Preemergence herbicides should normally be applied in early to mid-April in southern Iowa, mid-April to May 1 in central Iowa, and late April to early May in northern areas of the state.