Submitted to: Imported Fire Ants Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/15/2002
Publication Date: 8/20/2002
Citation: Oi, D.H., Williams, D.F. 2002. Mechanisms of Intercolony Transmission of Thelohania solenopsae in Red Imported Fire Ants. Imported Fire Ants Conference Proceedings. p. 21-22. Interpretive Summary:
Technical Abstract: The natural mechanism of intercolony transmission of Thelohania solenopsae, a pathogen of imported fire ants, is unknown. Inoculations of T. solenopsae in ten southern U.S states in 1998-2000 resulted in infections in 9 of 15 inoculation sites. However, sustained, expanding infections occurred only in polygyne S. invicta populations, which are not territorial, and presumably share brood among colonies. Infections in monogyne colonies generally were not found after initial detection except in Florida where infection had been detected for 3 years, but with little spread. Thus, there is circumstantial evidence that the movement of infected brood among polygynous colonies facilitates infection and spread. For territorial, monogynous imported fire ants, we hypothesized that brood raiding may be a mechanism of horizontally transmitting T. solenopsae. Male and female alates that were beginning their mating flights had infection rates of 80%. In addition, newly mated queens that produced infected colonies were collected and reared in the laboratory from 1999 to 2001. Average lifespan of these queens was 127 days ranging from 33 to 652 days (n=25) and colonies contained all life stages (i.e. eggs, larvae, pupae, and adults). Thus, it is evident that small, T. solenopsae infected incipient colonies can be produced. It also is possible that these incipient colonies are susceptible to brood raiding. To determine if imported fire ant colonies can become infected with T. solenopsae via brood raiding, 7 pairs of S. invicta colonies consisting of a large uninfected and a small, infected colony were given access to each other in the laboratory. T. solenopsae infection was detected in 4 of 7 of the large colonies. In the 4 large, infected colonies, brood levels declined an average of 69% after 22 weeks in contrast to an 88% increase in the controls. This further indicated that T. solenopsae infection had established and was impacting the fire ant colonies inoculated through brood raiding. Thus, sharing of infected brood and brood raiding are two ways T. solenopsae can be transmitted between colonies of red imported fire ants.