Submitted to: Ecological Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/6/2013
Publication Date: 4/1/2014
Citation: Resasco, J., Porter, S.D., Sanders, N.J., Levey, D.J. 2014. Testing sodium limitation of fire ants in the field and laboratory. Ecological Entomology. 39:267-271. Interpretive Summary: Understanding dietary requirements of pest ants assists with both developing effective baits to control them and rearing these ants for laboratory tests. A small amount of salt has been shown to improve the consumption of liquid baits. Scientists at the University of Florida, the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL and the University of Tennessee cooperated in studying the effects of salt baits on red imported fire ant foraging and on colony growth. Results showed that fire ants recruit strongly to salt water baits (1% and 2%) in regions with naturally low salt deposition (Savannah River, SC) but not in areas with high salt deposition (North Florida). Access to salt solutions (0.01%, 0.1%, 1%), however, did not improve the growth of laboratory colonies fed a low salt diet. This study suggests that the addition of salt to baits will likely improve their uptake in inland areas with low natural salt deposition. Salt availability, however, did not improve the growth of laboratory colonies, probably because the laboratory diet already contained sufficient salt.
Technical Abstract: 1) Sodium is an essential dietary element and preferential foraging for high concentrations of sodium by inland herbivorous and omnivorous ants suggests it may be limiting. If so, increased sodium availability through altered deposition and anthropogenic sources may lead to increased colony growth and cascading ecological impacts. 2) For red imported fire ants, Solenopsis invicta Buren, we test (a) whether colonies from coastal and inland sites differ in responses to salt baits and (b) whether supplemental NaCl increases growth of fire ant colonies in the laboratory. 3) Fire ants responded roughly an order of magnitude more strongly to high concentrations of NaCl baits in inland sites with low sodium deposition than did fire ants in costal sites with high sodium deposition. 4) Laboratory reared fire ants, however, showed no signs of sodium limitation or benefits of increased sodium. The link between behavioral responses to baits in the field and effects on colony growth, deserve further investigation to assess the ecological impacts of altered sodium availability.