Distribution of natural enemies and efforts to relocate Solenopsis invicta virus 3 into hybrid fire ant populations in Tennessee

Imported fire ants infest 66 Tennessee counties.  Red IFA (Solenopsis invicta Buren) (RIFA) dominates southern states, but Tennessee is mostly black IFA (Solenopsis richteri Forel) (BIFA) (~25.3%) or RIFA×BIFA hybrid (HIFA) (~74.1%), disconcerting RIFA-focused classical biocontrol. 

Objectives: Determine Tennessee incidence of Solenopsis invicta viruses (SINV-1, -2, or -3) and Kneallhazia solenopsae Kneall Alan Hazard, and SINV-3 relocation from Florida RIFA to Tennessee HIFA populations.  Tennessee IFA regulated area was divided into 14-by-14 km grids, and one colony sampled near grid centers summer/fall (August-October; 2015 and 2016; n=440) and winter/spring (January-April 2016; n=227).  Worker ants were collected for species and molecular pathogen assessment.  During winter/spring, two BIFA colonies had K. solenopsae and one HIFA colony had SINV-1.  During summer/fall, SINV-1, -2, -3 and K. solenopsae infected 2, 0, 0, and 2 BIFA and 24, 1, 6, and 4 HIFA colonies, respectively.  One RIFA colony had SINV-1 in summer/fall.  Incidence was 4.2%, 0.2%, 0.9%, and 1.2% SINV-1, -2, -3, and K. solenopsae, respectively.  SINV-3 occurred mostly in east Tennessee, K. solenopsae in west, SINV-2 only mid-state Rutherford Co., and SINV-1 statewide.  No colonies had multi-pathogen infections common in Florida RIFA.  During 2017-2019, Florida RIFA SINV-3 was inoculated into Tennessee HIFA at Giles, Lawrence, and Hamilton Counties without successful infections.  A hybrid SINV-3 variant was detected during inoculations (https://doi.org/10.1128/genomeA.01273-17). Based on the identified need (i.e., low infections) and ineffectiveness of RIFA SINV-3 in HIFA sites, future relocation efforts should focus on HIFA SINV-3 variant in Tennessee.