Көмекші заттардан жасалған зиянкестерге қарсы қолданылатын қоспа.

Chemical mixture used as a pest control agent

In horticulture, lime sulfur (lime sulphur in British English, see American and British English spelling differences) is mainly a mixture of calcium polysulfides and thiosulfate (plus other reaction by products as sulfite and sulfate) formed by reacting calcium hydroxide with elemental sulfur, used in pest control. It can be prepared by boiling in water a suspension of poorly soluble calcium hydroxide (lime) and solid sulfur together with a small amount of surfactant to facilitate the dispersion of these solids in water. After elimination of any residual solids (flocculation, decantation and filtration), it is normally used as an aqueous solution, which is reddish yellow in colour and has a distinctive offensive odor of hydrogen sulfide (H2S, rotten eggs).

A New York State Agricultural Experiment Station recipe for the concentrate is 80 lb. of sulfur, 36 lb. of quicklime, and 50 gal. of water. Transferring this formula to the metric system and using a total volume as 100 L of purified water to this we will add 19.172 kg of sulfur and 8.627 kg of calcium oxide. About 2.2:1 is the ratio (by weight) for compounding sulfur and quicklime; this makes the highest proportion of calcium pentasulfide. If calcium hydroxide (builders or hydrated lime) is used, an increase by 1/3 or more (to 115 g/L or more) might be used with the 192 g/L of sulfur. If the quicklime is 85%, 90%, or 95% pure, use 101 g/L, 96 g/L, or 91 g/L; if impure hydrated lime is used, similarly increase its quantity. Avoid using lime that is less than 90% pure. Boil for an hour, stirring and adding small amounts of hot water to compensate for evaporation.

In agriculture and horticulture, lime sulfur is sold as a spray to control fungi, bacteria and insects. On deciduous trees it can be sprayed during the winter on the surface of the bark in high concentrations, but as lime sulfur can burn foliage, it must be heavily diluted before spraying onto herbaceous crops, especially during warm weather. Lime sulfur is approved for use on organic crops in the European Union and the United Kingdom. Bonsai enthusiasts use undiluted lime sulfur to bleach, sterilize, and preserve deadwood on bonsai trees while giving an aged look. Rather than spraying the entire tree, as with the pesticidal usage, lime sulfur is painted directly onto the exposed deadwood, and is often colored with a small amount of dark paint to make it look more natural. Without paint pigments, the lime sulfur solution bleaches wood to a bone white color that takes time to weather and become natural looking. In the very specific case of the bonsai culture, if the lime sulfur is carefully and very patiently applied by hand with a small brush and does not enter into direct contact with the leaves or needles, this technique can be used on evergreen bonsai trees as well as other types of green trees. However, this does not apply for a normal use on common trees with green leaves. Diluted solutions of lime sulfur (between 1:16 and 1:32) are also used as a dip for pets to help control ringworm (a fungus), mange and other dermatoses and parasites. Undiluted lime sulfur is corrosive to skin and eyes and can cause serious injury like blindness.

Lime sulfur reacts with strong acids (including stomach acid) to produce highly toxic hydrogen sulfide (rotten egg gas) and indeed usually has a distinct "rotten egg" odor to it. Lime sulfur is not extremely flammable but combustion produces highly irritating sulfur dioxide gas. Safety goggles and impervious gloves must be worn while handling lime sulfur. Lime sulfur solutions are strongly alkaline (typical commercial concentrates have a pH over 11.5 because of the presence of dissolved sulfides and hydroxide anions), and are harmful for living organisms and can cause blindness if splashed in the eyes. The corrosive nature of lime sulfur is due to the reduced species of sulfur it contains, in particular the sulfides responsible for stress corrosion cracking and the thiosulfates causing pitting corrosion. Localized corrosion by the reduced species of sulfur can be dramatic, even the mere presence of elemental sulfur in contact with metals is enough to corrode them considerably, including so called stainless steels.

Lime sulfur is believed to be the earliest synthetic chemical used as a pesticide, being used in the 1840s in France to control grape vine powdery mildew Uncinula necator, which had been introduced from the USA in 1845 and reduced wine production by 80%. In 1886 it was first used in California to control San Jose scale. Commencing around 1904, commercial suppliers began to manufacture lime sulfur; prior to that time, gardeners were expected to manufacture their own. By the 1920s essentially all commercial orchards in western countries were protected by regular spraying with lime sulfur. However by the 1940s, lime sulfur began to be replaced by synthetic organic fungicides which risked less damage to the crop's foliage.