Summer annual weeds can be an eye-sore for all turfgrass sites. Weeds, in general, like to invade sites where turfgrass is weakened and where the overall density of the turf has been reduced. Therefore, maintaining a healthy, dense turf is the best approach for weed management. But, if you do have problems with these summer annual weeds, there are a number of pre-emergent herbicides that can be used to control these pests.
Summer annuals like crabgrass, goosegrass, grassbur, and prostrate spurge germinate in the late winter, early spring, and into summer. These are annual plants that come back each year by seed. Control of these weeds can be accomplished, but one has to apply the correct pre-emergent herbicide at the proper time. Remember, we are controlling germinating seeds—so the pre-emergent needs to be put out prior to germination. Weeds which germinate late, after the pre-emergent herbicide has begun to break down, may require a post emergent herbicide application to maintain a weed free lawn.
Pre-emergent herbicides are available in liquid and granular formulations and in either case uniform coverage at the correct rate is necessary for optimum results. Irrigation is required to incorporate the herbicide into the soil where it will be effective in preventing weed emergence. Generally 1 inch of irrigation is considered sufficient. When making herbicide applications care should be taken to avoid contact with non-target sites (i.e. flower beds). Many bedding plants are very sensitive to herbicide residues in the soil.
Finally, read the labels on all pesticides prior to application and calibrate your sprayer/spreader to insure proper application. If you are uncomfortable with your ability to accurately apply pesticides, you may want to consider hiring a professional applicator.
For more information contact Monti Vandiver, Extension Agent-IPM, Bailey and Parmer Counties at (806) 272- 4583 or 806-481-3300.