Monday, December 11, 2006 - 10:23 AM

Interaction of broadcast baits and native ants for the control and re-invasion of Solenopsis invicta

Alejandro A. Calixto,, Charles L. Barr,, and Marvin K. Harris, Texas A&M University, Department of Entomology, College Station, TX

Higher densities of S.invicta in the US relative to South America are explained by the absence of natural enemies and lack of strong interspecific competition. Despite advances in S.invicta management using biological control agents, broadcast baits remain as the primary tool for effective control. However, the effects of baits on native ants are relatively unknown. Understanding these effects is critical for S.invicta management since native ant competition may enhance the effect of introduced biological control agents. A pilot study documented that the impact of baits was greater on S. invicta and that the majority of unaffected ant species had a positive response to the reduction of S. invicta. This showed that baits and native ants are not always incompatible. We explored strategies to combine the use of baits with interspecific competition. Our goals are to determine whether different types of S.invicta management procedures affect native ants and to determine, if they are not affected, how they contribute to slow re-invasion of S. invicta. We conducted experiments on three sites in Texas using a BACI-P design. Sites were treated with methoprene and indoxacarb baits. Ants were monitored using pitfall traps and hot dogs. Plain bait was applied and species collecting grits were recorded. Preliminary data indicates that different management methods did not impact native ants and that S. invicta is significantly affected, this species discovered and collected more than 98% of broadcasted bait. Whether or not the presence of unharmed native ants slowed S. invicta re-invasion yet remains to be seen.

Species 1: Hymenoptera Formicidae Solenopsis invicta (red imported fire ant)