Most manufacturers package oil sprays. Brand names include Volck, Superior and Dormant Spray. Organic gardeners use only the oil, while others find that adding diazinon increases the effectiveness. If pear trees are sticky and turn black in the summer, add Thiodan to the spray. Read and follow all label directions to protect yourself and desirable organisms.
Purchase dormant oils at any nursery or garden center. Do not confuse dormant oil sprays with dormant disease-control spray. Dormant disease control is a lime sulfur spray that controls peach leaf curl and other diseases that are not common in this area.
Vegetable oils are also insecticidal, although the type of oil can greatly affect its activity. Cottonseed oil is considered the most insecticidal of the vegetable oils. Soybean oil, the most commonly available vegetable oil used in cooking, also provides some control.