To mulch or smother weeds often is considered mechanical, even though it simply excludes light rather than physically disrupting weed growth. Biological control methods use an organism to disrupt weed growth. Often the organism is an insect or disease and a natural enemy of the weed. This is called classical biological control. Classical is not the only form of biological control.
Livestock can be effective weed-management tools if used correctly.
Generally biological control is environmentally sound, particularly classical biological control. Chemical control methods use herbicides to disrupt weed growth. The first rule of any pesticide use is to read the label before using the product and follow all directions and precautions. Plant injury or death can occur. A weed-management system uses two or more control methods.