sulphur dust

Powdered sulphur, used as an insecticide (especially against mites and scale insects) and as a fungicide, particularly in the control of mildew. It gives off sulphur dioxide when ignited and is thus often used as a *fumigant. It is also mixed with soil to kill soil-borne pathogens. Elemental sulphur, in combination with calcium hydroxide and water, forms lime sulphur, an orange-coloured liquid used to kill various mites and to control peach leaf curl, scab, and powdery mildew.