Weeds create problems in lawns by ruining the uniform appearance. Invasive species take over portions of a lawn that are not properly maintained. Herbicides are chemicals used for the control of weeds in lawns. When properly applied, herbicides either prevent the growth of weeds, or destroy them by disturbing their physiology.
Pre-emergent herbicides destroy weeds by preventing the germination of their seeds. For effective application, pre-emergent herbicides are applied two to three weeks before the seeds germinate, says the University of Minnesota Extension. Pre-emergent herbicides are most effective against annual weeds that have a yearly production of seeds.
Post-emergent herbicides are used to kill weeds that already grow in the lawn. Herbicides in this category are broken down into selective and nonselective varieties. Selective focuses on one type of weed, such as broad leaf or grassy weeds. Nonselective herbicides kill all plants that they come in contact with.
Pre-emergent herbicides are applied using a fertilizer spreader. In granular form, pre-emergent herbicides require a light application of water to activate. Post-emergent herbicides are often sprayed on to the plant foliage, says the University of Arkansas. This requires an herbicide-spraying device.
Herbicide Application Safety
Herbicides have safety information on the label that advises the user on proper use. Safety clothing is required during application to prevent contact with the skin and eyes. It is best practice to buy the smallest amount of pesticide needed for weed control in your lawn, says the University of Hawaii at Manoa, to reduce the need for storage and to prevent over application. A wind free day with no chance of rain are best for the spraying of liquid herbicides to prevent drifting. Children and pets are not allowed in the area where herbicides are being mixed. Smoking while mixing is also prohibited.
A tightly sealed, non-corrosive container is required for the proper storage of left-over pesticides. A locked shed with a concrete floor keeps the covered container out of reach and prevents seepage into the soil. The sealed container is never stored near food and water. Do not store the container near food preparation equipment.