The Brazilian agricultural sector is responsible for most of our country's economic gains. Among the most significant crops is cotton, the most important textile fibre used in the spinning and clothing industries, as well as being used to extract oils and proteins used in food. Despite its potential, the increase in the number of pests in cotton crops has caused significant economic losses. Among the pests that affect the cotton plant is the apple caterpillar, Heliothis virescens, which can attack up to 15 plant structures, causing irreversible damage and major losses in production. This pest is mainly controlled using chemical insecticides, which, among other consequences, can lead to the development of resistance. In order to find an alternative that is more effective, cheaper and has the least environmental impact for controlling this pest, the aim of this study was to assess the specificity and bioinsecticidal potential of entomopathogenic filamentous fungi on the cotton apple caterpillar.