Endothall

Endothall (3,6-endoxohexahydrophthalic acid) is used as an herbicide for terrestrial and aquatic plants. It is used as an aquatic herbicide for submerged aquatic plants and algae in lakes, ponds and irrigation canals. It is used, as a desiccant on potatoes, hops, cotton, clover and alfalfa. It is used as a biocide to control mollusks and algae in cooling towers.

Endothall is a selective contact herbicide that has been used to manage submerged aquatic vegetation for over 50 years. The herbicide damages the cells of susceptible plants at the point of contact but does not affect areas untouched by the herbicide, like roots or tubers (underground storage structures).

The chemical formula for endothall is C8H10O5. Its Chemical Abstracts Service (CAS) name is 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid. It is an organic acid but is used as the dipotassium salt or the mono-N, N-dimethylalkylamine salt. It is considered safe in drinking water by the EPA up to a maximum contaminant level of 0.1 mg/L (100 ppb). Some people who drink water contaminated above this level for many years experience stomach or intestine problems.

Endothall is chemically related to cantharidin. Both compounds are protein phosphatase 2A inhibitors.