ARS | Publication request: Characterization of Solenopsis invicta (Hymenoptora: Formicidae) populations in Virginia: Social form genotyping and pathogen/parasitoid detection

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2009
Publication Date: March 24, 2010
Citation: Allen, H.R., Valles, S.M., Miller, D.M. 2010. Characterization of Solenopsis invicta (Hymenoptora: Formicidae) populations in Virginia: Social form genotyping and pathogen/parasitoid detection. Florida Entomologist. 93(1): 80-88.

Interpretive Summary: The red imported fire ant was introduced into the United States in the 1930s and currently infests about 300 million acres. It causes approximately $6 billion in damage annually and can pose a serious threat to human health. Spread of this pest ant within the United States is apparently continuing with recent reports from Virginia authorities that fire ants may be established in Virginia. Studies were formally conducted by an ARS scientist, Imported Fire Ant and Household Insects Research Unit, Gainesville, Florida, and scientists in the Department of Entomology, Virginia Tech, Blacksburg, Virginia, to document the population composition of the red imported fire ant in Virginia and to determine whether or not any biological control agents currently available for control of this ant are present. Evidence indicates that the red imported fire ant is firmly established in Virginia with both social forms, monogyne and polygyne, present. Interestingly, the biocontrol agents Kneallhazia solenopsae, Pseudacteon decapitating flies, and Solenopsis invicta virus 1 are all present in the Virginia fire ant population. This information provides formal documentation of the Virginia infestation and characterization of the biocontrol agents within this population.

Technical Abstract: 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. K. solenopsae was detected in eleven of twenty six colonies (42%). In addition, Pseudacteon spp. flies were detected in two (7.7%) colonies. The sampled colonies were also examined by reverse transcription PCR (RT-PCR) for the presence of Solenopsis invicta viruses -1 and -2. Results indicated that five 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.