Infection of red imported fire ant (Hymenoptera : Formicidae) colonies with the entomopathogen Thelohania solenopsae (Microsporidia : Thelohaniidae)

Thelohania solenopsae Knell, Alien, & Hazard is an entomopathogenic microsp oridium that infects imported fire ants. We documented artificially initiat ed transmission of T. solenopsae among colonies of the red imported fire an t, Solenopsis invicta Buren. Microsporidian transmission was initiated by p roviding colonies with brood (mixture of eggs, larvae, and pupae) from infe cted S. invicta colonies. Inoculated laboratory colonies of S. invicta had significantly less brood and adults than control colonies; after 23-29 wk, there was at least 88% less brood in the inoculated colonies. Lower egg lay ing rates, queen weights, and queen survivorship was also documented from i nfected colonies. Thus, T. solenopsae slowly debilitates an S. invicta quee n so that reproductive capacity diminishes and early death results. Artific ial inoculations resulting in infection and spread of T. solenopsae among r ed imported fire ant colonies under field conditions was also demonstrated for the 1st time.