Articles by Jim Gainan

As published in the Billings Gazette

Gardening Today: Dormant Spraying

Dormant Spraying
Dormant spraying is one of the easiest, most effective of all the spraying you will do in a growing season. Dormant disease control spray is lime sulphur. Lime sulphur helps to prevent diseases from occurring during the growing season by killing disease causing spores that over winter on tree and shrub buds, twigs and bark. These same spores can also over winter on fallen leaves. Be sure to rake and dispose of leaves if you know you have a disease problem.

Insect Control
For insect control, use Bonide Dormant Spray Oil or Volck Oil. They are 97% petroleum oil. The oil will smother insect eggs over wintering in the same places as the fungal spores. These two products can be mixed together at the rate of 5 tablespoons Bonide Dormant Spray Oil or Volck Oil and 5 tablespoons Lime Sulphur for excellent control of insects and disease.


Dormant spraying, true to its name, is applied when your outdoor trees and shrubs are in their dormant stage. The best time for application is in March and April before the trees or shrubs begin to leaf.

When you spray, apply it to all branches, trunks and ground area until the point of run-off. Be careful when spraying around the house, sidewalks, etc., as the lime-sulphur will stain.

Dormant spray can be applied to all trees, shrubs, rose bushes and any other deciduous (leaf bearing) outdoor woody shrubs.

We don't recommend dormant spraying for evergreens. The oil can reflect the sun on your evergreens and cause foliar burn.


How Often
Spraying twice a year during the dormant season (spring and fall) will greatly reduce the chance of having to spray throughout the growing time.

Dormant spraying is one of the safest and economical sprays available.