Crabgrass is one of the most common weeds in local lawns. It germinates when soil temperatures are approximately 60 degrees for 3-5 days at the 1/4-inch soil depth. It flowers and sets seed in July and dies with the first frost of fall.
Crabgrass has amazing abilities to survive and reproduce. Because of this, it is unrealistic to expect a crabgrass free lawn. You cannot eradicate crabgrass, or any other pest for that matter. A few crabgrass plants in your lawn are acceptable.
There are two methods to limit crabgrass in your lawns. The first, and preferred way, to keep crabgrass in check is to fertilize, water and mow properly. These cultural methods help the desirable grasses outcompete and crowd out the crabgrass and other weeds. The second method, crabgrass preventers, are spread over a lawn and create a chemical barrier that prevent the seeds from sprouting.
In our climate, water is another key to lawn success. Our turf needs about 2 to 3 inches of water a week to thrive, depending on soil type and temperature. Having an irrigation system set to automatically water once a day is not a good watering program. Water should be applied in large amounts, about 1 to 1.5 inches per application, and infrequently. This allows the turf to develop good, deep healthy roots.
In hot weather, you may need the sprinklers to run two or three times a week. In cooler weather, you can cut that back to once or twice a week if rainfall doesn’t occur. For this type of watering program, you need to know how much water you are applying and how much rainfall has occurred, so a rain gauge or a straight-sided cup can serve as an aid.
Mowing height and frequency are the important factors in cultural weed control. Do not scalp a lawn! This exposes soil, weed seed and reduces grass/weed competition. Our common turf grasses in northern Indiana should be mowed at 2½ to 3 inches in height. Do not remove more than 1/3 of the grass blade at any one time. At times of rapid growth, you may find it necessary to mow every three days.
Clippings are about 98 percent water and do not contribute to thatch, so they can be blown back on the lawn. If you find you need to pick up clippings because of matting, you are probably not mowing frequently enough.
Often, crabgrass preventers are combined with fertilizers as weed-and-feed products. 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 mostly quick-release nitrogen such as urea or ammonical nitrogen. Better yet, look for preventers that contain no fertilizer at all.
Do not use crabgrass preventers 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. Some of the more common crabgrass preventers contain benefin, oxadiazon, benefin/trifl uralin, pendimethalin, dithiopyr and prodiamine.
credit:goshennews.com