First report of a member of the <i>Fusarium oxysporum</i> species complex associated with <i>Diabrotica speciosa</i> larvae and adults collected from soybean fields in Brazil

Abstract Soil‐borne pathogens of the Fusarium oxysporum species complex (FOSC) reduce soybean production, yet their mechanisms of dispersal in the field conditions remain insufficiently understood. Diabrotica speciosa is a widespread pest in South America, but its potential role in disseminating soil‐borne fungi needs further research. This study evaluated the carriage and contribution of D. speciosa to disperse FOSC members in soybean fields. Larvae and adults of D. speciosa were collected from two commercial areas and dissected and fungi associated with their cuticle, mouthparts, digestive tract and prothorax were isolated. Seven fungal genera were recovered and a FOSC member was consistently detected in all larval body parts and in multiple regions of adults of D. speciosa . Morphological and phylogenetic analyses confirmed its placement within FOSC and it induced characteristic root rot symptoms in soybean in pathogenicity assays. This is the first characterisation of the fungal microbiota associated with distinct body regions of D. speciosa and also the evidence of an interaction between this insect and a FOSC member. These findings revealed an unrecognised pathway for FOSC dissemination in soybean systems with new insights into the epidemiology of soybean root rot, with implications to develop more effective management strategies.