Fitness Effects of Viral Infection on the Invasive Red Imported Fire Ant

Summary

The red imported fire ant, Solenopsis invicta, is a serious invasive pest species in the United States and elsewhere for which current control methods have failed to alleviate enormous population buildups and the consequent economic and ecological damage. New methods of control of S. invicta will likely rely on knowledge of natural predators, parasites, and pathogens of the ant. We investigated the effects of infections by three different viruses on colony-founding S. invicta queens and their incipient colonies for nine fitness-associated traits. We detected significant differences between infected and uninfected queens for several of these traits, suggesting that manipulation of viral loads in the field may lead to novel biological control strategies for this pest.

Situation

The red imported fire ant, Solenopsis invicta, was inadvertently introduced into the United States early in the past century and has spread rapidly throughout the southern part of this country as well as into California and other regions of the world, including the Caribbean, Australia, New Zealand, Taiwan, and China. The economic impact of fire ant infestations is enormous, with current estimated costs of control, medical treatment, and damage to property in the United States alone greater than $6 billion annually. Current methods of control have done little to alleviate the rapid spread and enormous population buildups of this invasive pest ant.

Response

New methods of control of S. invicta will likely rely on knowledge of the natural enemies of the ant, including known predators, parasites, and pathogens. We conducted a survey of the effects of three different naturally occurring RNA viruses on nine fitness-related traits of colony-founding queens and their incipient colonies. These carefully conducted studies featured large sample sizes and detailed observations under controlled conditions of the effects of viral infection on traits key to successful colony establishment. Such studies rarely have been undertaken previously with natural enemies of S. invicta.

Impact

Our results showed that queens infected with one of the viruses (SINV-2) displayed lower initial weight (fat reserves), greater weight loss during the colony-founding period, a longer duration of the founding period, lower initial weight of their newly founded colony, and slower subsequent colony growth than uninfected queens. These differences likely result in substantial reductions in the success of SINV-2-infected queens in founding new colonies in the wild. The results indicate that further study of SINV-2 infection dynamics is warranted to explore its potential application as a biopesticide of S.invicta in its invasive range.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2013
• Geographic Scope: National
• County: Clarke
• Program Areas:
  • Agriculture & Natural Resources