Fruit trees are dormant when the leaves have fallen from the limbs. During this time spider mites, scale insects and aphids may have already laid eggs on the bark of the fruit trees. Spraying dormant fruit trees with a petroleum-based product (called "dormancy oil spray") is effective in suffocating these insect eggs. According to the Colorado University extension service, the dormant oil spray should be sprayed just prior to the bud emergence of the fruit tree. The dormant oil spray must not be sprayed if freezing weather is predicted, as damage can occur to the tree.
Mix the dormant oil spray according to the label directions. There are many dormant oil products in varying strengths on the market.
Apply the dormant oil spray one week prior to the buds breaking open. Spray the tree on a calm and dry day to accelerate the drying process.
Cover each limb portion of the fruit tree with the oil spray. The dormant oil spray is only effective if it covers the entire tree.
Inspect the tree the following day to ensure good coverage. Respray the dormant oil if areas on the tree are not fully covered.