Several microorganisms have been reported from Phytoseiulus persimilis. Some microorganisms, including bacteria (Rickettsiella, Wolbachia) and virus-like particles, have not been studied in detail. Microsporidia cause debilitating, sub-lethal effects and may contribute toward poor predator performance. The accumulation of birefringent crystals causes prominent disease-like symptoms; however, effects on fecundity are observed only when symptoms become severe.