In recent years, the use of unmanned aerial vehicles has become popular in the development of agricultural and forestry applications. Due to the importance of plants in both rural and urban environments, the extraction of information from remote sensing data is a relevant research area; such information is fundamental for urban and rural planning, establishing sustainable ecological niches, estimating crop yields, conducting forest inventories, monitoring agricultural management systems and some other agricultural applications. In this article, a systematic review of the literature concerning the use of unmanned aerial vehicles in applications related to vegetation detection and plant inventory is presented. Likewise, an analysis of the main computational and statistical techniques used for processing unmanned aerial vehicles images is also made.