Manipulation of Viral Titers of Solenopsis invicta Virus-1 by RNA Interference in Laboratory Colonies of Red Imported Fire Ant

The red imported fire ant, Solenopsis invicta Buren, native to South America, is an economically important urban pest that has few natural enemies in the southern United States. Solenopsis invicta virus-1 (SINV-1) is a picorna-like single-stranded positive-sense virus known to affect only S. invicta. RNA interference (RNAi) is a known regulator of RNA viruses in biological systems and is an emerging biologically based insect control method. The purpose of this study was to increase, then decrease viral titers of SINV-1 in S. invicta colonies during a period of 1 month to demonstrate a possible use of SINV-1 as a targeted, controllable management strategy against S. invicta. Manipulation of SINV-1 viral titers was attempted by first exposing S. invicta colonies to SINV-1 and after 15 days exposing the same colonies to novel double-stranded RNA (dsRNA) coded for SINV-1 viral capsid genes. S. invicta colonies were monitored during the 1-month period, and significant increases and decreases in viral titers of SINV-1 were noted. Significantly more workers in S. invicta colonies exposed to SINV-1 died than did similarly sized noninfected S. invicta colonies during 30 days. Increases and decreases of viral titers of SINV-1 directly correlated with the increases and decreases in mortality.