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When to apply dormant oil or lime sulphur?

  • Botanical Garden
English

Dormant oil is a horticultural oil (mineral oil) applied when a plant is dormant. This low-impact pesticide is used to treat trees and shrubs vulnerable to attack by insects (particularly scale insects) and mites.

Lime sulphur is mainly used on trees and shrubs as a fungicide (e.g. against apple and pear scab). This low-impact pesticide also affects insects and mites.

Horticultural oil and lime sulphur may be used when the plants are dormant (in spring, before the buds open), or in lower concentrations during growth. During dormancy, horticultural oil may be combined with lime sulphur, in accordance with the manufacturer’s guidelines. During growth, you must wait at least 30 days between applying horticultural oil and lime sulphur.

In the dormant period, horticultural oil may be sprayed before the buds open and when there is no chance of rain or frost in the 24 hours following application. For the most effective results, it is preferable to wait until the daytime temperature reaches 12-15 oC three to four days in a row. Applying too soon will not produce satisfactory results. However, applying too late (when the buds have started opening or are already open) may cause damage.

Warning: Read the product label carefully before use to find out how to apply, plus the precautions to take during treatment, the risk of phototoxicity for certain plants, etc. Always keep pesticides out of reach of children.

To learn more, read our page about mineral oil and our page about calcium sulphide

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