Seed dressings were devised to prevent diseases caused by a wide variety of seed-borne plant-pathogenic fungi, to protect the germinating seeds against secondary infections, and to increase crop yields. Various chemicals, including several heavy metals, have been used as fungicides to treat seeds since the end of the nineteenth century. The effectiveness of these fungicides was greatly increased when aryl organomercurials were introduced around 1914. They had a wider spectrum of fungicidal activity than nonmercurial formulations and were used extensively until the mid-1980s to control fungus diseases through their application as seed dressings on many grains, vegetables, and nuts, as well as to protect fruit trees, rice, turf grasses, and golf courses. However, with the introduction of the more effective alkyl mercury compounds in the 1930s, especially methyl mercury and ethyl mercury, severe poisoning incidents followed. In developing countries hundreds of people died or...