Horticulture/Roundup

Roundup is the brand name of a systemic, broad-spectrum herbicide produced by the United States company Monsanto. It is the most used herbicide in the world, and the top-selling agrichemical of all time. Monsanto developed and patented the glyphosate molecule in the 1970s, and marketed Roundup from 1973. It retained exclusive rights in the US until its US patent expired in September, 2000, and maintained a predominant marketshare in countries where the patent expired earlier.

Uses
Weeds and grass will generally re-emerge within one to two months after usage. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide. Due to the absorption being limited to foliage, soil-bound glyphosate is effectively inert.

Action
The active ingredient of Roundup is the isopropylamine salt of glyphosate. Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the amino acids tyrosine, tryptophan and phenylalanine. It is absorbed through foliage and translocated to growing points.

Precautions
The surfactants used in the Roundup products may cause health issues. Like all herbicides, Roundup should only be applied in accordance with all labeling and legal requirements.

The US Environmental Protection Agency, the EC Health and Consumer Protection Directorate, and the UN World Health Organization have all independently concluded that glyphosate is not carcinogenic.

The toxicity of Roundup has been questioned, not so much because of its active agent (glyphosate) but because of the inactive ingredients, including the surfactant polyoxy-ethyleneamine (POEA). These components are responsible for "acute" toxicity to humans such as eye irritation. Ingestion of Roundup has been proven to cause diarrhea following extremely high exposures.

Roundup has also been found by researchers at Texas Tech University to disrupt the expression of steroidogenic acute regulatory protein (StAR) which has a role in testosterone production in males.

Resistance
Due to heavy use of the herbicide, and its glyphosate-tolerant counterpart plants, fears have arisen that repeated exposure and cross breeding may eventually cause unwanted plants and weeds that might mutate into Roundup tolerant forms effectively creating a superweed.