Chemical Composition and Mode of Action
Lime sulphur is formed by reacting calcium hydroxide (hydrated lime) with elemental sulfur under boiling aqueous conditions, yielding calcium polysulfides (CaSx).
Upon exposure to atmospheric oxygen and carbon dioxide after spraying, it decomposes to form a fine film of elemental sulfur and calcium thiosulfate.
The sulfur vapor interferes with fungal mitochondrial respiration, while the alkaline polysulfides soften and penetrate insect and scale waxy coatings.
- Chemical active: Calcium polysulfides in aqueous concentrate
- Multi-action profile: Acts simultaneously as a protective fungicide, acaricide, and dormant insecticide
- Zero resistance risk: Multi-site surface disruption prevents pathogens from developing chemical resistance
Target Diseases and Orchard Applications
Lime sulphur is extensively used in deciduous fruit orchards during the dormant winter window.
Applying before spring bud-break eliminates overwintering fungal spores, scale insects, and dormant mite eggs without risking foliar phytotoxicity.
- Apple and pear: Dormant spray against apple scab (Venturia inaequalis), powdery mildew, and San Jose scale
- Grapes: Winter wash to control overwintering anthracnose and powdery mildew spores on dormant canes
- Tea: Management of red spider mites and pink mites during cold weather periods
Application Guidelines, Mixing, and Temperature Warnings
Never apply lime sulphur during hot weather when ambient temperatures exceed twenty-eight degrees Celsius, as severe foliar sulfur scorching can occur.
Allow at least twenty to thirty days between lime sulphur applications and oil-based horticultural sprays to avoid phytotoxic leaf damage.
Applicators must wear full personal protective equipment due to strong caustic alkalinity and sulfur odor.
- Dormant timing: Best applied during winter dormancy before vegetative green buds swell
- Oil incompatibility: Never mix or follow within thirty days of petroleum oil sprays
- Safety gear: Wear chemical goggles, protective rubber gloves, and an approved vapor respirator
Official source
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Central Insecticides Board & Registration Committee ↗Related on KisanPe
Common questions
What is lime sulphur primarily used for in fruit orchards?
It is primarily used as a dormant winter spray to eradicate overwintering fungal spores, scale insects, and mite eggs on fruit trees.
Why should lime sulphur not be applied in hot weather?
Applying sulfur compounds in temperatures above 28°C causes severe foliar burning and fruit russeting.
Can lime sulphur be mixed with horticultural mineral oils?
No, combining lime sulphur with horticultural oils causes severe phytotoxicity; maintain a gap of at least 3 to 4 weeks between them.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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