Lime-sulfur is a widely used pesticide with insecticidal, miticidal, and fungicidal properties that is labeled, in general, for control of insects, mites, and diseases including scales (e.g., San Jose scale), mites (twospotted spider mite, Tetranychus urticae), powdery mildew, black spot, and rust. It is used extensively on fruit trees to combat numerous diseases such as peach leaf curl (Taphrina deformans). It is interesting to note that lime-sulfur was first used as an insecticide in the USA in 1880 and the first instance of insecticide resistance occurred in 1908 with San Jose scale, Quadraspidiotus perniciosus developing resistance to lime-sulfur sprays.
The active ingredient is calcium polysulfides. Organosulfurs are useful because they have ovicidal activity or kill insect or mite eggs. The sulfur component of the formulated active ingredient is what provides miticidal activity, thus preventing the build-up of mite populations. Lime-sulfur is produced by boiling lime and sulfur together. The compound is strictly a contact pesticide with limited residual activity. As such, thorough coverage of all plant parts is important in order to obtain control of insect and mite pests and diseases.
However, lime-sulfur applications should never be performed when ambient air temperatures exceed 85ºF. Applications should be made in spring prior to buds swelling and again in fall after leaves drop. Labeled rates vary from 1/2 fl oz/1 gallon to 4 fl oz/1 gallon with applications made at 10 to 15 day intervals in the summer. It is important to avoid using horticultural oils (e.g., petroleum-based) for several weeks after applying sulfur because sulfur residues may cause horticultural oil sprays to create phytotoxic reactions in plants. Many commercially available products contain a “Danger” signal word on the label. However, some formulations of lime-sulfur may be used in so-called “organic gardens.” Always be sure to read the label prior to using lime-sulfur or any pesticide, and wear the appropriate protective clothing (e.g., respirator).
For more information contact:
Raymond A. Cloyd
Professor and Extension Specialist in
Horticultural Entomology/Integrated Pest Management
Kansas State University
Department of Entomology
123 Waters Hall
Manhattan, KS 66506-4004
P – 785.532.4750