Solenopsis invicta virus 3: infection tests with adult honey bees (Hymenoptera: Apidae)

Solenopsis invicta virus 3 (SINV-3) is a positive sense, single-stranded RNA virus that has considerable potential as a self-sustaining or classical biocontrol agent against the invasive fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) because it can cause substantial mortality in colonies of this species. Based on extensive host specificity tests with other ants, we predicted that SINV-3 would not infect the honey bee, Apis mellifera L. (Hymenoptera: Apidae). Nevertheless, because of the economic importance of honey bees, it was necessary to confirm this prediction before proceeding with field release of SINV-3 into regions where it does not yet occur. To test our prediction, we 1) examined field bees for the presence of the virus, 2) conducted specific searches of the GenBank databases for sequences (amino acid and nucleotide) with identity to SINV-3, and 3) inoculated laboratory groups of honey bees with large doses of SINV-3. SINV-3 was not detected in field bees or in GenBank libraries associated with honey bees, Apoidea, or non-host Insecta generally. Western blot analysis for SINV-3 capsid proteins showed that viral proteins were not produced in inoculated honey bees, but were produced in inoculated fire ants. Furthermore, qPCR analysis revealed no significant increase in SINV-3 quantity in honey bees, beyond the inoculating dose, whereas virus quantity dramatically increased over time in inoculated fire ants. Based on these results, we conclude that field release of SINV-3 as a biocontrol agent against red imported fire ants in regions without the virus would pose little or no threat to honey bees.