Insect-pathogen interactions can be modulated by other organisms present in the ecosystem. Perhaps the clearest example of this is the observation that baculovirus infectivity depends on the host plant on which the insect feeds. This is because plant produced compounds can influence the physiological condition and magnitude of the immune response of the insect. We have observed that the presence of other pathogenic and non-pathogenic microorganisms can also influence the infective process. During the last years we have also observed, in the study of the interaction of S. exigua with its baculovirus, that the gut microbiome, and also other RNA viruses producing unapparent infections, significantly altered the susceptibility of the insect to baculovirus infection.