Information on Herbicides

Identification

• Chemicals used to cut back or even kill plant growth are called herbicides. The proper application of herbicides depends greatly on agronomic, ecological and economic factors.

Systematic vs. Contact Herbicides

• Contact herbicides work best on annual weeds and only target the parts of the plant where the chemical was actually deposited. For more complete dispersal, systematic herbicides are absorbed by the plant roots and tissue, spreading the chemicals throughout the entire plant system.

Selective Herbicides

• Selective herbicides target specific weeds without damaging a valuable crop in the process. According to Purdue University, scientists are also working on developing crop varieties with increased tolerance to herbicides.

Nonselective Herbicides

• Nonselective herbicides kill vegetation indiscriminately. Entire areas of vegetation can be eliminated or significantly damaged with nonselective herbicides, prompting the need for increased caution and situation control.

Pre-Emergence vs Post-Emergence

• Pre-Emergence herbicides attack vegetation while the seeds are still germinating and can be applied two to three weeks in advance of a weed's growth. Post-Emergence herbicides are designed to kill vegetation that has already broken ground. This is a more reactive treatment and can require several applications.

Agent Orange

• The US military developed a virulent herbicide to clear away jungles during the Vietnam War. The herbicide's code name was Agent Orange and an estimated 19 million gallons were used during the war.