Controlling Crabgrass Needs to Start Now

I know it is difficult to think about controlling summer weeds when you are wearing a winter jacket, but crabgrass starts early. By the time you may notice it in the summer, control cannot be achieved. If you had crabgrass last summer you can be sure it is coming back again this year. You need to start thinking about applying a pre-emergence herbicide now.

Crabgrass pre-emergence herbicides need to be applied when soil surface temperatures reach about 55 degrees F for three consecutive days. Typically, 55-degree soil temperature is when Forsythia (yellow bells) is blooming, which is typically the end of February.

You only want to use a crabgrass pre-emergence herbicide if you have a thick, healthy, established lawn. If you have a weak or thin lawn you will want to control crabgrass with a post-emergence herbicide. The reason for this is that pre-emergence herbicides inhibit roots from growing into the soil. So if you need to encourage more grass you do not want to inhibit grass root growth.

Balan (benefin) is a pre-emergent herbicide for crabgrass control that is safe on all turf grass except bent grass. Do not apply to a lawn seeded the previous fall or to newly sprigged turfgrass. You can find this herbicide in a product called Team. Other pre-emergence products include benefin and oryzalin, benefin and trifluralin, bensulide, dithiopyr, DCPA, metolachlor, napropamide, oryzalin, pendimethalin, or prodiamine. Check the label for grass tolerance and application rates.

Besides proper timing of the pre-emergence herbicide you must also have 1/2 inch of water to active it. Too much water will wash it to far into the soil, too little will not form the herbicide barrier needed to discourage crabgrass seed germination. Calibration also is very important to make sure you are putting out the correct amount of herbicide. Too much is an environmental risk, too little provides inferior control. One way to avoid over applying a herbicide is to apply a split application. Put half on when the soil temperature reaches 55 degrees then apply the other half six weeks later. This is a good idea anyway since crabgrass can emerge over a long period of time in the spring.

Some post-emergence herbicides are Vantage that is safe to use on established centipede lawns. Do not apply until 3 weeks after spring green up. Vantage can be used on newly planted centipede after three inches of new stolon growth. MSMA is a herbicide found in many products and is safe to use on bermuda (wire grass), fescue and zoysia. MSMA with repeated applications can also control some other summer weeds such as bahiagrass, nutsedge, and sandspur.

Read the herbicide label for recommended rates and proper application practices. The use of trade names in this article does not constitute endorsement of one product to the exclusion of similarly labeled products.

Date Created: 2/5/2004.