Crabgrass, also known as digitaria, can be killed by applying pre-emergent herbicides during the right season. A more preventative measure involves ensuring that green grass stays healthy and well-nourished, as this can prevent the spread of crabgrass and make the use of herbicides less of a necessity.
- Aerate lawn before applying herbicide
Pre-emergent herbicides form a barrier that keeps crabgrass from growing and spreading. This barrier can be punctured and rendered ineffective if a lawn aerator is used following application. Complete all lawn aeration before using herbicides on the lawn.
- Decide which herbicide to use
Dimension and Tupersan are recommended for killing crabgrass; however, both have pros and cons. Dimension is more proficient at disrupting the life cycle of crabgrass over a prolonged period of time but is not safe for all types of lawn grass. Tupersan, meanwhile, is not harmful to normal grass seed but does not offer the long-lasting coverage of Dimension.
- Apply herbicide before germination of crabgrass seeds
Crabgrass seeds germinate when the soil temperature reaches approximately 55 to 60 degrees Fahrenheit. If herbicide is applied following germination, the crabgrass is likely to still spread. In the early to middle parts of spring, apply herbicide about 2 inches beneath the ground before the soil temperature reaches 55 degrees Fahrenheit. Lilac bushes bloom during the same time crabgrass seeds germinate, making them an effective indicator of when to use herbicide.