Hidden Allies: Endophytic Fungi in Fruit Orchards as Biological Control Agents of Agricultural Pests—A Systematic Review

Fruit production represents a major agricultural sector worldwide; however, it is severely affected by pests that reduce fruit yield, quality, and marketability. The intensive use of chemical insecticides has generated environmental contamination, resistance in pest populations, and risks to human health, increasing the demand for sustainable alternatives. In this context, endophytic fungi (EF) have gained relevance as biological control agents due to their ability to colonize plant tissues and produce bioactive metabolites that affect agricultural pests. This systematic review aimed to evaluate the current scientific knowledge regarding EF as biological control agents against pests in fruit crops and to analyze the tripartite interactions among fungi, plants, and pests. The review was conducted following PRISMA guidelines using the databases Web of Science, Scopus, PubMed, and OpenAlex. Studies were selected according to predefined exclusion criteria focused on the simultaneous presence of endophytic fungi, fruit crops, and agricultural pests. A total of 24 fruit species, 51 endophytic fungi, and 33 agricultural pest species were identified. The most frequently reported fungal genera were Penicillium, Cladosporium, Fusarium, Aspergillus, Gnomoniopsis, and Trichoderma, while a broad diversity of pest species affected by these fungi was recorded. Interaction analyses revealed complex and highly interconnected tripartite relationships, in which some fungi exhibited strong host specificity whereas others displayed broader interaction ranges. The findings demonstrate that EF possess significant potential as sustainable biological control agents in fruit production systems. However, research in this field remains limited and fragmented, highlighting the need to develop standardized models, validate their efficacy under field conditions, and conduct studies focused on the commercial scalability of EF-based management strategies.