A fungicide is a chemical that kills fungi, the tiny plant-like organisms that obtain their nourishment from dead or living organic matter. Examples of fungi include mushrooms, toadstools, smuts, molds, rusts, and mildew.
Fungicides can be important in protecting crops from the growth of fungi that cause disease (pathogens). The first known fungicide was sulfur, a naturally occurring substance. One of the most effective of all fungicides, Bordeaux mixture, was invented in 1885. Bordeaux mixture is a combination of two inorganic compounds, copper sulfate and lime.
With the growth of the chemical industry during the twentieth century, researchers invented synthetic fungicides. Ferbam, ziram, captan, naban, dithiocarbonate, quinone, and 8-hydroxyquinoline are examples of synthetic fungicides.
Compounds containing mercury and cadmium were popular fungicides. Methylmercury was widely used by farmers in the United States to protect growing plants and treat stored grains.
During the 1970s, however, evidence of a number of adverse effects of mercury- and cadmium-based fungicides began to emerge. The most serious effects were observed among birds and small animals who were exposed to sprays and dusting or who ate treated grain. A few dramatic incidents of methylmercury poisoning among humans, however, were also recorded. The best known of these, although not related to fungicides, was the 1953 disaster at Minamata Bay, Japan, in which residents of the area developed nervous disorders ultimately linked to methylmercury in fish they had eaten. The fungicides affected their ability to walk, caused mental disorders, and, in some, caused permanently disability.
The problems with mercury and cadmium compounds spurred the development of less toxic substitutes for the more dangerous fungicides. Dinocap, binapacryl, and benomyl are examples of less toxic compounds.
Another approach has been to use integrated pest management and to develop plants that are resistant to fungi. The latter approach was used with great success during the corn blight disaster of 1970. Researchers worked quickly to develop strains of corn that were resistant to the corn-leaf blight fungus and by 1971 had provided farmers with seeds of the new strain.
Research has also identified natural fungicides, which include tea tree oil, cinnamaldehyde, neem oil, and rosemary oil. The bacterium Bacillus subtilis can also function as a fungicide.
A problem with many fungicides is the development of resistance by the target organism, similar to the development of resistance by disease-causing bacteria to antibiotics. If the resistance arises because of a genetic change in the target organism, the resistance can be passed on to subsequent generations. As with antibiotics, a particular fungicide may need to be replaced with another as resistance develops.
A small number of fungi (around 200) are a health threat to humans and cause fungal infections. Even fewer (between 20–25 species) are the cause of common fungal infections in humans. Many fungal infections are a nuisance but cause no serious health threat. If a person has good health and seeks medical treatment in a timely manner, most fungal infections can be quickly and easily treated. However, in people with compromised immune systems (e.g., those infected with HIV or receiving cancer treatment) fungal infections can cause serious health problems.
See also Fungal infections .
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Richardson, Malcolm D., and David W. Warnock. Fungal Infection: Diagnosis and Management, 4th ed. Chichester, West Sussex, UK: Wiley-Blackwell, 2012.
American Osteopathic College of Dermatology. “Fungal Infections: Preventing Recurrence.” http://www.aocd.org/skin/dermatologic_diseases/fungus_preventing.html (accessed October 30, 2012).
MedlinePlus. “Fungal Infections.” http://www.nlm.nih.gov/medlineplus/fungalinfections.html#cat1 (accessed October 17, 2012).
National Pesticide Information Center. “Fungicides.” http://npic.orst.edu/RMPP/rmpp_ch15.pdf (accessed October 30, 2012).
Pennsylvania State University. “Potential Health Effects of Pesticides.” http://pubs.cas.psu.edu/freepubs/pdfs/uo198.pdf (accessed October 30, 2012).
National Pesticide Information Center, Oregon State University, 333 Weniger Hall, Corvallis, OR, 97331-6502, (800) 858-7378, firstname.lastname@example.org, http://npic.orst.edu .
David E. Newton, EdD
Revised by Tish Davidson, AM