Some science behind the scenes


Herbicides, also commonly known as weedkillers, are pesticides used to kill 'unwanted plants' [ie unwanted by the person who is killing them]. Herbicides are widely used in commercial agriculture and landscape turf management. In the US, they account for about 70% of all agricultural pesticide use, and ....

 “Some herbicides are used in forestry, pasture systems, and management of areas set aside as wildlife habitat [sic]”.

 There are two types of herbicide:

  • Selective herbicides kill specific targets, while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic mimics of natural plant hormones.
  • Non selective herbicides – which may be used to clear waste ground, industrial sites, railways and railway embankments are not selective and kill all plant material with which they come into contact.

Some plants produce natural herbicides, such as the genus Juglans (walnuts), or the tree of heaven; such action of natural herbicides, and other related chemical interactions, is called allelopathy.

For a list see Alan Woods compendium of pesticides

USA figures

Herbicide safeners, on the other hand are chemicals used in combination with herbicides to make them "safer" - that is, to reduce the effect of the herbicide on crop plants, and to improve selectivity between crop plants vs. weed species being targeted by the herbicide. Herbicide safeners are used to pretreat crop seeds prior to planting, or they are sprayed on plants as a mixture with the herbicide - again see Alan Wood's Compendium for a list 


For iPad/iPhone users: tap letter twice to get list of items.