- Lime sulfur
In
horticulture , lime sulfur (British spelling lime sulphur) is a mixture ofcalcium polysulfide s formed by reactingcalcium hydroxide withsulfur . It can be prepared by boiling calcium hydroxide and sulfur together with a small amount ofsurfactant . It is normally used as an aqueous solution, which is reddish-yellow in colour and has a distinctive offensive odour.Use
Lime sulfur is sold as a spray for
deciduous trees to control fungi,bacteria andinsect s living or dormant on the surface of thebark . Lime sulfur burns leaves so it is not as useful forevergreen plants.Bonsai enthusiasts use undiluted lime sulfur to bleach and sterilise portions of trees to give an aged look known as "Jin".Diluted solutions of lime sulfur (between 1:16 and 1:32) are also used as a dip for pets to help control
ringworm . (Note that undiluted lime sulfur is corrosive to the skin and will cause serious injury.)Safety
Lime sulfur reacts with strong
acid s (including stomach acid) to produce highly toxichydrogen sulfide (rotten egg gas) and indeed usually has a distinct "rotten egg" odour to it. Lime sulfur is not extremely flammable but combustion produces highly irritatingsulfur dioxide gas.Safety
goggles andglove s should be worn while handling lime sulfur. Lime sulfur solutions are stronglyalkali ne (typical commercial concentrates have apH over 11.5), and so it is corrosive to living things and can causeblindness if splashed in the eyes.History
Lime sulfur is believed to be the earliest synthetic chemical used as a pesticide, being used in the 1840s in
France to controlgrape vine powdery mildew "Uncinula necator", which had been introduced from the USA in 1845 and reducedwine production by 80%. In 1886 it was first used inCalifornia to control San Jose scale. Commencing around 1904, commercial suppliers began to manufacturer lime sulfur; prior to that time, gardeners were expected to manufacture their own. By the 1920s essentially all commercialorchard s in western countries were protected by regular spraying with lime sulfur. However by the 1940s, lime sulfur began to be replaced by synthetic organicfungicide s which risked less damage to the crop's foliage.References
* [http://entweb.clemson.edu/pesticid/history.htm Chronological History of the Development of Insecticides and Control Equipment from 1854 through 1954]
* [http://www.pestmanagement.info/pesticide_history/Two.pdf Background on History of Pesticide Use and Regulation in the United States, Part Two] (PDF, 54 kB).
* [http://www.croplifefoundation.org/Documents/Pesticide%20Benefits/Fungicides/Final%20Report/Assembled%20Full%20Report%209-12-05.pdf The Value of Fungicides in U.S. Crop Production] , (PDF, 1.1 MB)
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