Diseases and pests are a problem even in greenhouse crops, problem which has to be solved without threatening the plant. Crop protection requires frequent updates in information and therefore sensor networks that are real time monitoring systems are the ones that can deliver such information. The purpose of this paper is to present a way of preventing the appearance of diseases and pests in a greenhouse by using a monitoring system composed of an integrated sensor network. Our sensor system is doing a real time monitoring of the following parameters in the greenhouse: light intensity, soil moisture and temperature, air temperature and humidity and air temperature at canopy level; all of the data being stored using a software made by "Tedelco". A real time monitoring camera is also used for pest and disease detection. A pot experiment, using beans, was established inside the greenhouse to test the applicability of the system. In order to assure the optimal conditions for the inhibition of pests, the greenhouse is also equipped with an artificial lighting system specially designed for greenhouses, an irrigation system and an artificial fog system. Sensor systems are the ideal support for preventive monitoring and at the same time it offers all the support data necessary for decision making regarding crops development.