Diquat dibromide is a nonselective, fast-acting desiccant herbicide, which damages only the parts of a plant to which it is applied. It is used agriculturally and also has a number of outdoor residential weed control applications.
Diquat dibromide binds strongly with soil, and has a low mobility in the environment.
Diquat dibromide may be sold under names such as Aquacide, Aquakill, Dextrone, Diquat, Reglone, Reglox, Reward, Tag, Torpedo, Vegetrole, and Weedtrine-D (#EXTOXNET).
Diquat dibromide is a colorless to yellow crystal that is red in solution. It is odorless. It is highly soluble in water and has a high affinity for soil (#CEPA).
Because highly concentrated forms of diquat chemicals are corrosive, they often contain corrosion inhibitors (#CEPA).
Diquat dibromide is registered for weed control on several food crops including potato, carrot, cucumber, melons, pepper, radish, squash, and turnip. In addition, it is also used on some feed crops, most notably alfalfa. It may also be used to defoliate the tops of some seed or root crops. Diquat dibromide can be used to treat irrigation systems and agricultural drainage systems (#EPA).
Residentially, diquat dibromide may be used to control weeds around ornamental plants and trees, as well as in lawns. It can also be used on paved areas, patios, fencerows, or hedgerows (#EPA).
Diquat dibromide targets a variety of plants such as algae: pithophora, spirogyra; and weeds: bladderwort, crabgrass, elodea, jimsonweed, leafy spurge, naiad, poison ivy, salvinia, shepherdspurse, and waterlettuce (#EPA).
Human Health Effects
Diquat dibromide has a moderate acute toxicity. The oral LD50 is 120 mg/kg for rats, 233 mg/kg in mice, and 188 mg/kg in rabbits. Repeated dermal doses of diquat dibromide caused redness, thickening, and scabbing to the skin of rabbits. Workers handling highly concentrated diquat dibromide have reported color change, softening, and shedding of the fingernails (#EXTOXNET).
A study in which rats were fed diquat dibromide for 104 weeks found that cataracts occurred in nearly all test animals. Kidney functions were also disrupted. Another study in which dogs were fed diquat dibromide for one year found chronic intestinal inflammatory lesions and kidney weight increases in addition to a clouding of the eyes (#CEPA).
Inhalation of diquat dibromide may cause coughing and sore throat. Exposing the skin and eyes may cause redness and pain. Ingesting diquat dibromide may cause abdominal pain, diarrhea, nausea, vomiting, and ulcerations in the mouth (#PANNA). Extreme exposures can cause kidney failure or liver damage (#EXTOXNET).
Environmental Health Effects
Plants absorb diquat dibromide rapidly through the leaves. There, the chemical interferes with plant growth, and quickly destroys tissue necessary for translocation before it can move to other parts of the plant. The plant dies after diquat dibromide interrupts normal plant respiration (#EXTOXNET).
Diquat dibromide has a moderate acute toxicity to birds. The oral LD50 is 564 mg/kg for mallard, and 200 to 400 mg/kg in hens (#EXTOXNET). It has a slight to moderate toxicity to fish. The 8-hour LC50 is 12.3 mg/L for rainbow trout and 28.5 mg/L for Chinook salmon (#EXTOXNET). Diquat dibromide is not expected to bioaccumulate in fish. It is practically nontoxic to bees (#EPA).
Diquat dibromide binds strongly with soil, and has a low mobility in the environment. The half-life of diquat dibromide could not be calculated, since no noticeable deterioration of the chemical occurred in three year intervals. This suggests that diquat may accumulate in soil (#CEPA). Diquat dibromide is an unlikely water contaminant (#EPA).
Diquat dibromide is a General Use Pesticide.
Heating diquat dibromide may cause the release of toxic fumes (#NIOSH).
California Environmental Protection Agency. Public Health Goal for Diquat in Drinking Water. (August 2000). http://oehha.ca.gov/water/phg/pdf/diquat.pdf [Accessed 8-31-10].
Environmental Protection Agency. Reregistration Eligibility Decision- Diquat Dibromide. (July 1995). http://www.epa.gov/oppsrrd1/reregistration/REDs/0288.pdf [Accessed 8-31-10].
Extension Toxicology Network. Diquat Dibromide. (1996). http://extoxnet.orst.edu/pips/diquatdi.htm [Accessed 8-31-10].
National Institute for Occupational Safety and Health. Diquat Dibromide. http://www.cdc.gov/niosh/ipcsneng/neng1363.html [Accessed 8-31-10].
Pesticide Action Network North America. Diquat Dibromide. http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC33217 [Accessed 8-31-10].