Insecticides From Plants

stabilizer such as cane sugar to liquid lime-sulfur and evaporating to dryncss. Self-boiled lime-sulfur is made by utilizing the heat of hydration or slaking of quicklime, CaO, to carry on the reactions with sulfur. Ammonium polysulfide and sodium polysulfide are made by passing hydrogen Sulfide gas, H.^S, into ammonium or sodium hydroxide containing excess sulfur. It is supposed that the chemical reactions are similar to those taking place in the preparation of lime-sulfur. Sulfur is used under some conditions for the control of potato leafhopper, the cotton fleahopper, tomato psyllid, mites, and plant bugs. Organic sulfur compounds, including thiocyanates, xanthates, and thiuram disulfides, have some insecticidal properties although they are used largely as fungicides. Sulfur dioxide, SO2, made by burning sulfur, is sometimes used to kill insects in closed spaces. Thallium sulfate, Tl^SO^, sometimes is used as the toxic agent in ant poisons. Several zinc compounds are in limited use as insecticides. Zinc sulfate, ZnS04, is sometimes used in place of copper sulfate in reactions with hydrated lime to form a zinc bordeaux mixture that has special uses. Zinc chloride, ZnCl^, is used to protect against termites.