Some materials are systemic and are translocated through the plant. Thorough treatments are essential for success. Spraying the tops of a tree with a contact pesticide will not control the aphids that live on the undersides of the leaves. To get control you must know what you're fighting, and how to fight it. Mites on Alberta spruce require treating the inside of the plant.
Some scale insects require treating the truck and branches in addition to the foliage.
Some insects have more than one generation per year and require multiple treatments to get sufficient control. Date and time of application Name and address of the treatment site. Also, by keeping accurate records we can tell which pesticide performed better than others did and what timing was more effective. Proper calibration materials and save you money. Good pest control requires an integrated approach.