Dormant oil applications also control certain overwintered shade tree pests. Summer or foliar treatments are now possible for a variety of pests during the growing season. Oils also can be mixed with other insecticides, providing a broader spectrum and greater persistence of control. Spider mites, whiteflies and young stages of scales are common pests that can be controlled by oils during the growing season. Oils are sometimes applied to prevent transmission of viruses.
Oils also are useful against powdery mildew.
Diluted horticultural oils, often mixed with a small amount of baking soda, can be an effective control for this common plant disease. The neem oil products have been effective against several types of powdery mildew and rust. Some plant pests controlled by horticultural oils. Avoid drift onto sensitive plants. High temperature limitations are primarily related to the drought-stress status of the plant.