Herbicides for Weed Control in Grass

Characteristics

• Herbicides can be broken up into two main groups: selective or nonselective. Herbicides that are selective kill a specific weed while leaving other plants and grasses untouched. Consequently, selective herbicides are best used on established lawns that you do not plan on reseeding. Nonselective herbicides kill everything they touch. Nonselective herbicides are generally used when you plan to reseed the entire lawn. Herbicides can further be classified as pre-emergent or post-emergent. Pre-emergent herbicides are applied before weeds actually emerge from the soil, and post-emergent herbicides are applied after weeds have risen above the soil.

Application

• Herbicides are generally applied to lawns, using a fertilizer spread for granular herbicides or a sprayer for liquid herbicides. Keep in mind that if you are going to use either of these tools for application, you should avoid using them in the future for other purposes, such as fertilizing the lawn or watering the garden. This is because even a thorough cleaning may not remove all the herbicide residue. Timing and rate of application varies, depending on the herbicides, and thus you should always read the instructions printed on the package.

Herbicide Resistance

• Several weeds that could once be controlled with herbicides are now resistant, due to repeated applications. Moreover, a small number of plants have the tolerance to survive any herbicide application. Weeds can become resistant to a particular herbicide within anywhere from five to 20 years. Consequently, steps such as mixing herbicides, crop rotation and use of alternative weed control techniques should be used to combat herbicide resistance.

Dangers

• Herbicides are toxic, and thus extreme caution should be used whenever applying an herbicide. Improper use of herbicides can poison livestock, injure crops and lead to eye and skin infections. Moreover, herbicides can be carried by air movement to areas where herbicide application is not intended. This process, known as drift, can lead to the contamination of bodies of water and neighboring homes and gardens.