Characterization of Solenopsis invicta (Hymenoptera: Formicidae) populations in Virginia: social form genotyping and pathogen/parasitoid detection

Red imported fire ant, Solenopsis invicta Buren, workers were sampled from 26 colonies in Virginia during the 2007-2008 time period. Polymerase chain reaction (PCR) assays were used to determine colony social form (monogyny or polygyny) by genotyping ants at the Gp-9 locus. Twenty of the colonies (76.9%) were found to be polygyne. Multiplex PCR was also used to detect the presence of several organisms currently being used as biological control agents for fire ants in the U.S., including the microsporidian parasite Kneallhazia solenopsae and Pseudacteon spp. parasitioid decapitating phorid flies in the sampled colonies. Kneallhazia solenopsae was detected in 11 of 26 colonies (42%). In addition, Pseudacteon spp. flies were detected in 2 (7.7%) colonies. The sampled colonies were examined by reverse transcription PCR (RT-PCR) for the presence of Solenopsis invicta viruses -1 and -2. Results indicated that 5 colonies were infected with SINV-1 (19%) and none were infected with SINV-2. This study is the first to characterize the red imported fire ant infestation in Virginia and documents the presence of biological control agents in this area.