Trait Plasticity among Invasive Populations of the Ant Technomyrmex brunneus in Japan

Development of an effective hydrogel bait and an assessment of community-wide management targeting the invasive white-footed ant, Technomyrmex brunneus

BACKGROUND

Ants are one of the most serious household pests. White-footed ants in the genus Technomyrmex (Hymenoptera: Formicidae) are invasive species of increasing global importance as evidenced by recent range expansion, nuisance pest status in residential areas and control difficulties driven mainly by lack of effective bait products. The goal for the current study was to develop an effective hydrogel bait and community-wide management program for controlling the invasive T. brunneus in a residential area of Hachijo Island, Japan.

RESULTS

In laboratory insecticide screening, hydrogel baits containing thiamethoxam achieved higher T. brunneus mortality than those containing dinotefuran, imidacloprid, boric acid or fipronil at the concentrations tested. Hydrogel baits containing 0.01% and 0.001% thiamethoxam resulted in ≥90% mortality within seven days. However, the horizontal transfer effect was not strong with either concentration. Field experiments confirmed that hydrogel baits containing 10% and 30% sugar are highly attractive to T. brunneus. The community-wide treatment utilizing hydrogel bait containing 0.001% thiamethoxam and 30% sugar significantly suppressed T. brunneus. Town residents were given the opportunity to participate in the program by applying hydrogel baits around their homes, and a follow-up survey revealed that the residents regarded hydrogel baits as easy to apply and highly attractive and effective against T. brunneus.

CONCLUSION

The hydrogel bait and management program developed in this study can be used to suppress T. brunneus. Furthermore, our results demonstrate that a large network of highly motivated and properly trained members of the public can be highly effective in managing invasive ant populations. © 2022 Society of Chemical Industry.

Resilience of native ant community against invasion of exotic ants after anthropogenic disturbances of forest habitats

The positive association between disturbances and biological invasions is a widely observed ecological pattern in the Anthropocene. Such patterns have been hypothesized to be driven by the superior competitive ability of invaders or by modified environments, as well as by the interaction of these factors. An experimental study that tests these hypotheses is usually less feasible, especially in protected nature areas. An alternative approach is to focus on community resilience over time after the anthropogenic disturbance of habitats. Here, we focused on ant communities within a forest to examine their responses after disturbance over time. We selected the Yanbaru region of northern Okinawa Island, which is a biodiversity hotspot in East Asia. We compared ant communities among roadside environments in forests where the road age differed from 5 to 25 years. We also monitored the ant communities before and after disturbance from forest thinning. We found that the species richness and abundance of exotic ants were higher in recently disturbed environments (roadsides of 5–15 years old roads), where the physical environment was warmer and drier. In contrast, the roadsides of 25‐year‐old roads indicated the potential recovery of the physical environment with cooler and moister conditions, likely owing to regrowth of roadside vegetation. At these sites, there were few exotic ants, except for those immediately adjacent to the road. The population density of the invasive species Technoymex brunneus substantially increased 1–2 years after forest thinning. There was no evidence of the exclusion of native ants by exotic ants that were recorded after disturbance. Our results suggest that local ant communities in the Yanbaru forests have some resilience to disturbance. We suggest that restoration of environmental components is a better strategy for maintaining native ant communities, rather than removing exotic ants after anthropogenic disturbance.