Last updated 2/24/98
Control of Crabgrass
Zac Reicher and Clark Throssell
Crabgrass is the major weed infesting homelawns in Indiana. Crabgrass is an annual weed germinating in April, setting seed in August, and dying with the first frost of fall. Crabgrass has tremendous survival reproductive capabilities. Because of this, it is unrealistic to expect no crabgrass plants in your lawn. You cannot eradicate crabgrass (or any other pest for that matter); a few crabgrass plants in your lawn are acceptable.
Cultural Crabgrass Control
The most effective way to control crabgrass is to create a dense, healthy turf. A healthy turf will compete well with crabgrass and prevent it from establishing.
Often, cultural control alone will not control crabgrass satisfactorily, and herbicides may be needed. This is especially true in new lawns or lawns that are thin from damage or improper maintenance. When using herbicides and all pesticides, be sure to read, understand, and follow all label recommendations.
Preemergence herbicides prevent emergence of crabgrass plants. These products must be applied prior to crabgrass germination which could occur as early as April 1 in southern Indiana and three or more weeks later in northern Indiana. Purdue research has shown that these herbicides can be applied as early as March 1 and still be effective all season. It is essential to apply these products early in spring prior to crabgrass germination.
Often, preemergence herbicides are combined with fertilizers. Since fertilization should be minimized in the spring, purchase products with most of the nitrogen in slow release forms such as methylene ureas or sulfur or polymer coated ureas. Avoid products with most of the nitrogen as urea or ammonical nitrogen.
Do not use these products on new seedlings or before seeding an area. To be most effective, these products need to be watered- in after application. Refer to the label for specific instructions of each product.
|Common Names of Some|
Postemergence herbicides control crabgrass after it has emerged. These products are most effective on small crabgrass. These products are more difficult to use than preemergence herbicides and it is extremely important to follow label instructions. Keep in mind the following when using these products:
|Common Names of Some|
|MSMA (Methane sodium methyl arsonate)|
|DMSA (Dimethyl sodium arsonate)|
Do not attempt to control crabgrass after about July 15, because crabgrass is too large to control effectively. It is better to simply tolerate the crabgrass until it dies with the first frost.
By maintaining a dense lawn, you can limit the amount of crabgrass. Proper fertility, mowing, and irrigation is essential for crabgrass control; consider herbicidal control only if necessary.
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