Herbicides are classified in a number of ways based on how they are used. In using herbicides to control weeds in forages, timing of application is very important. Herbicides may be applied before planting seed for a new forage stand or may be used to control weeds in an already established stand. Proper timing will lead to adequate weed control, while improper application timing may result in a failure to control weeds adequately. The table below summarizes four commonly used herbicide timing terms.

Term Definition Example
Preplant Herbicides that are applied before planting the crop - typically from several days to just before planting EPTC, Glyphosate
Preemergence Herbicides applied anytime before the weed seedlings emerge through the soil surface Simazine
Postemergence Herbicides applied after the crop seedlings (or weed seedlings) have emerged through the soil surface 2,4-DB, bromoxynil
Established stands Herbicides applied after the roots systems have developed sufficiently enough to allow selective use. 2diuron, terbacil, hexazino

Herbicides are also classified as to their selectivity. Some herbicides are designed to control a broad range of weeds, while others are designed to control only selected types of weeds. The table below summarizes the two commonly used terms with regard to selectivity and gives an example of each category.

Term Definition Example
Selective Herbicide formulated to control specific weeds or weed categories. A material that is toxic to some plant species but less toxic to others. 2,4-D

(Selectively toxic to broadleaf weeds)


(a.k.a. Broad spectrum)

Herbicide formulated to control both broadleaf and grass weeds. Paraquat, Glyphosate



Herbicide Company Links



CWC Chemical www.cwc-chemical.com
R and D Sprayers www.co2sprayers.com
Round Up www.roundup.com
Sprout Less www.sprout-less.com