Monosodium methyl arsonate


Monosodium methyl arsenate is an arsenic-based herbicide. It is an organo-arsenate; less toxic than the inorganic form of arsenates. However, the EPA states that all forms of arsenic are a serious risk to human health and the United States' Agency for Toxic Substances and Disease Registry ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites.
It is a herbicide used against weeds in agriculture, combining selectivity, low weed-resistance, and cost-efficiency. Target weeds include: grasses and broad-leaf weeds including some weeds that are resistant to the herbicide Glyphosate.
Weed resistance to herbicides is on the rise due to the use of the herbicides in general, as well as in conjunction with the introduction of genetically modified crops. Resistant crops are endowed with natural resistance to certain herbicides, a resistance which they may impart to non-crops through cross pollination. There are very few, if any, new herbicides capable of economically combating the resistance problem. With the exception of isolated cases of common cocklebur Xanthium strumarium, no resistance build-up has occurred with the weeds that MSMA controls.
MSMA provides post-emergent selective annual grass and yellow nutsedge control, in cool season. MSMA can be used to control Convolvulaceae and Cyperus rotundus.
Arsenic is classified as a Group-A carcinogen. The EPA states that:
Trade names include: