Lime Sulphur

by Mark Paterson (edited 2011)

Contents: 1. How to use lime sulphur as a pesticide. 2. What is lime sulphur. 3. History of lime sulphur. 4. Bonsai and lime sulphur. 5. Safety.

1. How to use Lime Sulphur as a pesticide
Lime sulphur may be purchased at garden centres or other stores with garden departments. It is usually sold in a a two-pack with another product known as Dormant Oil. Lime sulphur is a combination fungicide/insecticide and dormant oil is an insecticide. For use, a mixture may consist of a dormant oil/ lime sulphur mix, dormant oil alone in a more dilute mix (known as horticultural oil), or lime sulphur alone, diluted in water.

Please mix the ingredients according to package directions. Spray your tree(s) with enough of the mixture to ensure good coverage (including underside of needles and leaves, without creating excessive runoff. The pot and soil surface should be covered to prevent the mixture from saturating the soil (where lime sulphur would likely have deleterious effects on beneficial micorrhyzal fungus growing in close association with the roots)

Dormant oil should not be used on Beech, Butternut, Colorado Blue Spruce, Cryptomeria, Junipers, Cedars, Spruce - especially Dwarf Alberta Spruce, Douglas Fir, Hickory, Holly, Maples, Walnuts, Redbud, Cotinus and the Delicious variety of apple.

A lime sulphur mixture can protect trees from a variety of pests including apple and pear scab, powdery mildew, rust mites, brown rot, black knot, certain mites, leaf spot, certain blights, scale insects, aphids, and ants. The pathogenic action of lime sulphur is through direct contact or fumigation by sulphur vapors.

Lime Sulphur should not be used on sulphur sensitive plants like blackcurrant, grape, lemon, currants, apricots and cranberry

Users of sulphur and sulphur-based pesticides should remember that sulphur is lethal to many beneficial insects as well as spiders and beneficial mites.

Also - lime sulphur may cause phytotoxicity in plants. This can range from yellowing to leaf drop. It is caused when Lime sulphur is applied to leaves, and when lime sulphur is mixed with other chemicals and oils than those specified as safe. The lime component moderates the phytotoxic effect of the sulphur. Usually the mixture is used in late winter/ early spring when temperatures are above freezing and before the tree leafs out. Lime sulphur can be used in the growing season (i.e., leaves present) if applied early in the morning or late afternoon - not in direct sun. Scorching effects are greater in hot weather or arid conditions.

2. What is lime sulphur?
Lime sulphur is a mixture of calcium polysulfides formed by reacting calcium hydroxide, slaked lime, with sulfur. It is most commonly sold as a premixed liquid concentrate of 30% calcium polysulfide.

Sulphur is an effective fungicide/insecticide. The pests absorb the sulphur, resulting in the sulphur being converted to hydrogen sulfide - which then disrupts electron transfer. Sulphur inhibits fungal spore germination.

Hydrated lime is highly alkaline (11.5) and corrosive in effect. It dissolves the binding agents of protein bundles, allowing it to penetrate insect - and human - tissues readily. It is effective against hard to kill insects like scale insects.

3. A little history
Lime is one of the oldest chemicals humankind has produced and elemental sulphur is readily available. Monsieur Grison, head gardener at Versailles in 1851 is credited with boiling these ingredients together with water to create lime sulphur for pest control. Until 1904, gardeners and commercial gardeners were expected to make their own lime sulphur, there was no commercial product. The boiling of hydrated lime and sulphur creates fumes which are highly corrosive,so making your own is not encouraged.

Lime sulphur and copper sulphur were the choices of grape farmers to control grapevine powdery mildew in France. It was used in the Americas by 1885 to control San Jose scale. By the 1920’s, the product was in common use. By the 1940’s, synthetic pesticide use was on the rise and replaced many of the uses of lime sulphur.

So far as I can tell, synthetic pesticides are better only in that they can be used on plants with foliage without as much risk of the phytotoxic effects. They are not necessarily more effective as pesticides, nor better for the environment.

4. Lime sulphur and bonsai
Ahh, yes. The last thing to note about lime sulphur. It is used by bonsai artists to bleach areas of jin and shari - exposed heartwood that enhances the effect of age and the battle with the elements. The artist paints the (very stinky) lime sulphur onto the exposed wood with a small paintbrush. For this, the product is quite perfect and the sulphur protects the wood from rot and insect damage. The whitening effect gives the wood an appearance very similar to that of aged, sun-bleached wood. Some artists mix a little soot or black paint with the lime sulphur to moderate the whiteness of the bleached wood. The effect appears in a few hours, or at most, a few days. The treatment needs to be reapplied periodically.

5) Saftey
Don’t let the warnings about lime sulphur deter you from using it. Lime sulphur is very effective when used properly. However, I advise you to heed the warnings on the label and wear appropriate protective gear!

Saftey Appendix:
Calcium polysulphide 22%
Reactivity & Under What Condition: Thermal decomposition.
Effects of Overexposure: Product is generally considered to
be of low to moderate toxicity, but may cause severe
irritation to eyes, nasal passages, throat and skin.
Corrosive to eyes and skin; may cause damage to eyes.
Sensitization of Material: Pre-existing skin or respiratory
disorders may be aggravated by excessive exposure to this
Respiratory Protection: OSHA/NIOSH approved respirator with
organic particulate cartridge.
Eyes: Goggles/Face Shield
Gloves: Rubber or Impervious
Footwear: Rubber or Impervious
Clothing: Coveralls or Impervious apron when handling
Other: Work in well ventilated area.
Leak & Spill Procedures: Use appropriate protective
clothing during clean up. Absorb with an inert material
such as sand, soil clay or vermiculite. Sweep up and
If On Skin: Remove all contaminated clothing. Wash skin and
hair thoroughly with soap and water. Wash clothing before
reuse. If irritation persists, get medical attention. Sources:

---------------- MATERIAL SAFETY DATA SHEET ---------------
United Agri
C:\Documents and Settings\Owner\Desktop\Mark's\Lime Sulphur toxicology sheet.htm