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

Authors: Porter, Sanford; Gavilanez Slone, Jenny; Valles, Steven

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2016
Publication Date: 12/15/2016
Citation: Porter, S.D., Gavilanez Slone, J.M., Valles, S.M. 2016. Solenopsis invicta virus 3: infection tests with adult honey bees (Hymenoptera: Apidae). Florida Entomologist. 99(4):729-733.

Interpretive Summary: Solenopsis invicta virus-3 (SINV-3) is a single-stranded RNA virus that has considerable potential as a self-sustaining biocontrol agent against the invasive fire ant, Solenopsis invicta because it causes substantial worker and colony mortality. This virus is found in fire ants in both the United States and Argentina, but it is not found in fire ant infestations in the Caribbean or the Pacific Rim. Based on extensive tests with other ants, scientists at the USDA Agricultural Research Service (ARS), Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL predicted that SINV-3 would not infect the honey bee, Apis mellifera. Nevertheless, because of the economic importance of honey bees, it is necessary to confirm this prediction before applying for field release of SINV-3 into regions where it does not yet occur. To test the prediction that SINV-3 would not infect honey bees, ARS scientists 1) examined field bees for the presence of the virus, 2) conducted specific searches of the GenBank databases for sequences 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. Western blot analysis for SINV-3 capsid proteins showed that viral proteins were not produced in inoculated honey bees. Furthermore, qPCR analysis revealed no increase in SINV-3 in honey bees, beyond the inoculating dose. In contrast, the virus dramatically increased over time in inoculated fire ants. These results are important because they provide strong evidence that field release of SINV-3 as a biocontrol agent against red imported fire ants would pose little or no risk to honey bees.

Technical Abstract: 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, 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. 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 examined field bees for the presence of the virus, conducted specific searches of the GenBank databases for sequences (amino acid and nucleotide) with identity to SINV-3, and 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, while 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 imported fire ants in regions without the virus would pose little or no threat to honey bees.