Despite the raise of awareness on the use of pesticides during the last 30 years, pesticide industries grew up thanks to the lack of information about the real damage these products could cause on the environment, human health and on producers’ incomes. The lack of knowledge using large and small scale fields led to an uncontrolled overuse of pesticides and to a consequent accumulation of pollutants in the soil and in the air. Additionally, treatment schedules, which correspond to a preventive defense planned through periodical treatments, were established without analyzing neither the harmful populations of pests (mostly insects, harmful for olive trees and olive plantations) nor the climate and weather conditions in which the insects could develop. This type of treatment was independent from the infections’ progress and from the effective risk. In the following text, harmful species are considered as the ones which are harmful to olive trees/olive plantations.