Do Mound Disturbance and Bait Placement Affect Bait Removal and Treatment Efficacy in Red Imported Fire ant (Hymenoptera: Formicidae) at Different Seasons?

Abstract

Abstract:This study provides empirical evidence that disturbing mound immediately before application, as opposed to label recommendation, did not reduce foraging activity of the red imported fi re ant, Solenopsis invicta Buren, except for about 10-min delay in foraging. Despite the delayed foraging, there was no signifi cant difference in the amount of baits foraged between disturbed and undisturbed colonies. Eventually, Ͼ96% of the baits were foraged, with the maximum removal occurred by 2 and 3 h, respectively, in summer and spring trial. The fastest and great amount of bait removal 1 h post-treatment occurred to baits placed on mound, followed by 0.18-0.3-m from mound base, and the slowest 1.08-1.2-m from mound base. All treatment gave 100% control 1 mo later, regardless of the season, without colony relocation or new colony invasion in the test plots. Keywords: solenopsis invicta, individual mound treatment, bait application, season effectThe red imported fi re ant, Solenopsis invicta (Buren) (Hymenoptera: Formicidae), is a major constant pest in agricultural and urban sectors in the southeastern United State 1,2 and has substantial impact on humans, wildlife, and agriculture. 3,4 One approach to manage fi re ants is the use of toxic baits in which a toxicant, a food attractant, and a carrier are combined into granular bait and applied broadcast or to individual mounds. Baits are often promoted to the public as the most practical, economic and effective component in integrated fi re ant management programs because they allow the dissemination of the active ingredients to an entire colony via social feeding behavior. 5,6 Registration labels on commercial fi re ant baits generally suggest, with no research-based data, not to disturb fi re ant mound and to place baits on the ground in a circle Ͻ1.2 m around the mound but not directly on mound. Despite the labels, homeowners and some pest control professionals still claim that applying bait on and around pre-disturbed mounds via foot-kicking or racking or shoveling provides better control. Up to date, research on baits has focused on what makes the best active ingredients 5,7,[8][9][10][11][12][13] or bait formulations. 14,15 The only research on the impact of not following label suggestions reported no signifi cant effect on mound disturbance concerning the total amount of bait removed by fi re ants. The research was conducted in winter season when foraging activity was low. 16 The resulting bait consumption was Ͻ44% regardless of whether the colonies were disturbed. Additionally, that study did not evaluate treatment effi cacy.Fire ants are known for seasonally changing foraging activity 17,18 and bait preference. 19 We conducted this study in spring and summer seasons of the year 2008. Our objectives were to determine: 1) whether disturbing mound before bait application reduces fi re ant foraging activity; 2) whether bait placed on mound is less accessible, as opposed to that around the mound; 3) whether mound disturbance will reduce treatment effi cacy; and ...