Early spring is the best time to apply dormant oil to fruit trees and other deciduous plants to help control insects and fungal diseases that overwinter in the bark. It is particularly effective on scale and mites but can also be used on the egg masses of gypsy moth if you can’t reach them to scrape them off. It works by coating the eggs of the insects, thereby smothering them and is considered safe for more beneficial insects as well as animals and people once dry.
You will want to spray your trees before the buds break open, on a dry, wind-free day where the temps are going be above freezing for at least 24 hours. Do not apply if the buds are already opening and make sure to move or cover any nearby plants that might be affected by overspray. Do not use dormant oil on maple, black walnut, spruce, cedar, juniper, smoke bush or redbud trees.
Mix the product according to the manufacturers directions and pour into a sprayer. Coat branches thoroughly until they are dripping wet.
Kits and a variety of sprayers are available in-store.