In recent years, the use of unmanned aerial vehicles for the development of agricultural and forestry applications has become popular. Given the importance of plants in both rural and urban environments, the extraction of information from data obtained by remote sensing is a highly relevant area of research. Such information is vital in urban and rural planning activities, the establishment of sustainable ecological niches, estimation of crop yields, the realization of forest inventories, the supervision of agricultural management systems, and some other agricultural applications. In this paper, we present a systematic review of the literature regarding the use of unmanned aerial vehicles in applications related to the detection of vegetation and plants inventory. Likewise, an analysis of the software used and the main computational and statistical techniques for the processing of images taken from unmanned aerial vehicles is made.