Herbicides for Lawns

• There are several different ways to classify herbicidal chemicals used on lawns; one of the most useful ways classifies herbicides according to when the herbicides are applied. Preemergent herbicides are typically applied when the lawn is in a dormant state in order to kill weeds before they sprout and begin to grow throughout the lawn. Postemergent herbicides are applied directly to weeds after they have begun to grow. Within each category are selective herbicides --- those designed to only kill specific plant species and leave other species intact --- and nonselective herbicides, which are those that simply kill all vegetation to which they are applied. If weeds have already begun to overtake your lawn, preemergent herbicides will be of little use to you, so a selective postemergent herbicide would be ideal for controlling an individual weed species, while a nonselective herbicide would be ideal for attacking multiple species.
  
  

Chemical Recommendations

• There are numerous different herbicidal chemicals commonly recommended for use on lawns. Herbicides containing glyphosate are commonly used for quackgrass, while herbicides containing 2,4-D, MCPP or dicamba can offer effective control of most species of broadleaf weeds. Other herbicidal chemicals frequently used on lawns include benefin, benefin + trifluralin, benefin + trifluralin + isoxaben, DCPA, isoxaben, pendimethalin, 2,4-D + 2,4-DP + MCPP, 2,4-D + MCPP + dicamba, 2,4-D + dicamba + MCPP +MSMA, glufosinate, MSMA and triclopyr + clopyralid. First identify the species that is invading your lawn, and then choose an herbicide that is labeled for control of that specific weed species.
  
  

Application Methods

• The lethal herbicidal chemical in postemergent herbicides must be absorbed through weed leaves, so, in general, liquid formulations offer more effective weed control than dry granular formulations. The addition of a surfactant, a chemical additive sometimes sold separately from herbicides and mixed with the herbicide prior to use, can augment the effectiveness of any herbicide by increasing the "stickiness" of the herbicide so it will not be washed away by wind, rainfall or any other natural factors.
  
  

Other Considerations

• An herbicide used in a manner not intended by the manufacturer can present potentially serious risks to your health and the environment. Airborne "drift" from herbicidal chemicals can make its way to other plants, shrubs and trees in your yard and injure them. Moisture runoff from lawns that are heavily contaminated with herbicidal chemicals can make its way to neighborhood water sources or natural bodies of water. To avoid these and other potentially hazardous situations, always exactly follow the manufacturer's instructions listed on the herbicide.