Get the jump on insect problems and more when you use a dormant spray kit.

Prevention really is the best way to keep your trees and shrubs healthy, and healthy plants mean more time to enjoy your beautiful garden.

Applying dormant spray is an essential part of good garden practice. At Peter Knippel Garden Centre, we often recommend dormant spray kits to prevent or control insect problems on trees and shrubs, and/or the effects of fungal diseases on fruit trees.

Dormant spray kits contain two products: Horticultural oil and lime sulphur. Both these products can be used individually to treat a variety of health and insect problems in plants. When mixed together, horticultural oil and lime sulphur form what we call 'dormant spray.' The mixture is applied using a sprayer, which may be a hose-end, backpack, or hand-held model.

Horticultural oil is a great low-impact pesticide. In this case, it is used to treat trees and shrubs that are particularly vulnerable to attack by insects like scale and mites. It works by smothering insects (or the eggs of insects) that overwinter in the bark of the tree.

Lime sulphur is a fungicide. It is used primarily to prevent fungal diseases that affect fruit on trees, such as apple and pear scab. When applied in fall, lime sulphur controls overwintering fungal diseases. When applied in spring, it will help prevent these diseases from becoming a problem during the growing season. It also has a secondary effect on insects and mites.

Both horticultural oil and lime sulphur can be applied in spring and fall. The timing of application of both these products is important.  

In spring, temperatures should be warmer than 5°C (ideally 12-15 C for three or more days in a row with no chance of rain or frost in the 24 hours following application) but before the leaf buds start turning green, called "bud break."

In fall, dormant spray can be applied when the leaves of the plant have died or fallen off but when the temperature is still above 5°C. Again, you will have the best results if the 24 hours following application are frost- and rain-free.

Some plants can be harmed by the application of these products. Incorrect application, including using dormant spray after bud break, can also harm plants. Make sure to read all instructions carefully, and check with one of our garden advisors if you are still unsure.