D3178: Foraging activity and the use of an improved hydrogel bait in managing invasive long-legged ant Anoplolepis gracilipes, on Oahu, Hawaii

Anoplolepis gracilipes is a widely distributed invasive species and has dispersed globally via human commerce pathways. We explored the foraging activity of A. gracilipes and the potential for an improved biodegradable alginate hydrogel to deliver liquid bait in managing this ant species. In the field, A. gracilipes peak foraging time were found to be between 0700h and 0900h and between 1900h and 2100h. Using the improved hydrogel baits that we developed, we tested the treatment of regular vs. improved hydrogel baits during their peak foraging time on three different field sites for each treatment. After a single treatment using the regular hydrogel baits, ant visits in the monitoring tubes in the field were reduced and showed significant differences when compared with the pre-treatment data by week 2 post-treatment. However, the ant visits in the monitoring tubes gradually rebounded and starting at week 6, the data showed no significant difference with that of the pre-treatment level. In contrast, after a single treatment using the improved hydrogel baits, the ant visits in the monitoring tubes remained low and showed significant differences when compared with the pre-treatment data by week 2 post-treatment through week 8, indicating considerable residual activity of the improved hydrogel bait treatment. The improved hydrogels have the ability to retain moisture for a longer period of time, and subsequently, attract and manage higher numbers of ant populations. Thus, this study demonstrates the potential of the improved alginate hydrogels as an effective delivery system for liquid baits to manage A. gracilipes.