Dormant Oil Spray

Dormant Oil Spray

This product is often sold as a kit containing Horticultural Oil and Liquid Lime Sulphur.  It is important to spray your roses, deciduous trees and shrubs, especially fruit trees, (avoid some evergreens) with a combination of Lime Sulphur and Dormant Oil to help kill over-wintering insect eggs and fungal spores.  This is a non-toxic material and not harmful to the environment.  It starts the plant material fresh and clean in the spring.  Be on the lookout during the growing season for new pests and problems.

Did you have trouble with Gypsy Moths last summer?  Be sure to spray vulnerable trees with dormant oil to eliminate any overwintering eggs.

The Dormant Oil is refined oil which is sprayed uniformly on the bark of trees and shrubs.  The oil suffocates any over-wintering insects or their eggs. 

Lime Sulphur can be sprayed when plants are dormant as well as on its own during the growing season to treat any fungal problems as this does not harm leaves.

It is best to spray before the buds begin to swell and break, showing green.  Spraying of dormant oil should occur on a clear day when temperatures are expected to remain over 5 deg C (40 deg F) for at least 24 hours.  Try to avoid applying dormant oil when severe freezing trends are expected in the 3 – 4 days following application.

If there are plants under the trees you plan to spray, covering them is a good idea as the dormant oil/lime sulphur can hinder the growth of perennials.  Sprays must not be applied to fruit trees in bloom as it will harm the bees trying to pollinate the fruit trees.  It should never be applied to blue spruce as it affects the colour of the needles.

CAUTION:  completely cover tender vegetation (ie. Pansies) BEFORE spraying nearby trees and vines with dormant oil.

Dormant Oil Spray Kits are available at Dufferin Garden Centre, $18.99