In recent years, the incidence of a new pest has been reported in Guatemalan fir plantations</p><p>(Abies guatemalensis), known as the Green Algae. It is characterized by a green cover that</p><p>grows on the leaves and blocks sunlight, causing wilting and necrosis of the branches. Leaves</p><p>showing signs of the Green Algae, were collected in three locations, and the algae and fungi</p><p>present in the samples were identified by means of in vitro culture, microscopy and molecular</p><p>analysis of the EF and ITS regions. Four terrestrial algae from the genera Desmococcus,</p><p>Klebsormidium (2) and the class Trebouxiophyceae, and 11 fungi from the genera Alternaria,</p><p>Aspergillus, Fusarium (3), Mucor (2), Trichoderma (3) and Ulocladium (1) were identified. It</p><p>was concluded that the algae cover is a biofilm made up of several species of epiphytic algae,</p><p>saprophytic, pathogenic and beneficial fungi that may vary according to location. Factors</p><p>affecting biofilm algal and fungal species richness and the symbiotic relationship between them</p><p>still need to be addressed.