Gardeners aren’t the only ones who enjoy fruit trees. Pests — like scales, aphids and mites — feast on the tender plant parts and overwinter on the fruit trees. Dormant oils control these annoying insects and are safe for use on fruit trees. Homemade dormant oils provide the same benefits as commercial oils without the costly price tag.
Dormant oils once included heavy oils which needed to be applied when the fruit tree has been in its dormant stage to stop damage to buds and foliage. Nowadays newer dormant oils are lighter, allowing them to be applied at anytime during the year without harming buds. Since you’re able to apply newer inactive oils during the season, the term “dormant” typically refers to the time where the oil is applied. Dormant oil is made up of refined petroleum oil which when applied to trees will smother overwintering insects — like aphids, scales and mites — and their own eggs or will dissolve their protective waxing coating. It is used in the winter months when fruit trees are in their inactive period. For dormant oil to provide appropriate control, the oil needs to come in contact with the insects.
Dormant Oil Recipes
Several dormant oil recipes can be found and help control insects on fruit trees. A dormant oil formulation developed by scientists at Cornell University controls overwintering insects and foliar diseases. It contains 2 tablespoons of ultrafine canola oil and 1 tablespoon of baking soda mixed with a gallon of water. Cornell University scientists also produced a nourishing formulation containing two tablespoons of horticultural oil, 1 tablespoon of baking soda, 1 tablespoon of kelp and 1 tablespoon of mild dish soap mixed with 1 gallon of water. Another dormant oil recipe comprises 2 tablespoons of baking soda, 5 tablespoons of hydrogen peroxide, 2 tablespoons of castile soap that can be made of an olive oil base — plus 1 gallon of water.
No matter which recipe you use, the application for the homemade dormant oil is the same. Through the fruit tree’s dormant stage — that is usually between November and early spring before bud break — fill out a pump sprayer using the homemade dormant spray and thoroughly coat the fruit trees — stems and both sides of the leaves — together with the oil. Never use dormant oil when the temperature is below freezing or when fruit trees are worried. Stressed trees are more likely to become damaged when treated with dormant oil. Furthermore, only use the oil spray when the fruit tree is dry. Moisture or high levels of humidity decrease the effectiveness of dormant oil sprays.
Dormant oils generally won’t harm beneficial insects since they’re applied at a time when valuable insects are not present on fruit trees and have a very low toxicity level to mammals and humans. Furthermore, dormant oils won’t leave unpleasant residue behind. It loses its ability to control insects once dried, however, and can harm plants prone to oil sprays. Cedars, maples, spruce and junipers are a couple of vulnerable tree species which dormant oil should not be used on.