Effect of Broadcast Baiting on Abundance Patterns of Red Imported Fire Ants (Hymenoptera: Formicidae) and Key Local Ant Genera at Long-Term Monitoring Sites in Brisbane, Australia

Abstract

In 2001, the red imported fire ant (Solenopsis invicta Buren) was identified in Brisbane, Australia. An eradication program involving broadcast bait treatment with two insect growth regulators and a metabolic inhibitor began in September of that year and is currently ongoing. To gauge the impacts of these treatments on local ant populations, we examined long-term monitoring data and quantified abundance patterns of S. invicta and common local ant genera using a linear mixed-effects model. For S. invicta, presence in pitfalls reduced over time to zero on every site. Significantly higher numbers of S. invicta workers were collected on high-density polygyne sites, which took longer to disinfest compared with monogyne and low-density polygyne sites. For local ants, nine genus groups of the 10 most common genera analyzed either increased in abundance or showed no significant trend. Five of these genus groups were significantly less abundant at the start of monitoring on high-density polygyne sites compared with monogyne and low-density polygyne sites. The genus Pheidole significantly reduced in abundance over time, suggesting that it was affected by treatment efforts. These results demonstrate that the treatment regime used at the time successfully removed S. invicta from these sites in Brisbane, and that most local ant genera were not seriously impacted by the treatment. These results have important implications for current and future prophylactic treatment efforts, and suggest that native ants remain in treated areas to provide some biological resistance to S. invicta.

Eradication of two incursions of the Red Imported Fire Ant in Queensland, Australia

“…McNaught et al . () showed that the baits had little effect on the local ant fauna and only one genus, Pheidole , was affected in a similar way to Red Imported Fire Ant. In addition, Pheidole spp.…”

“…The baits used by the programme contain pyriproxyfen and methoprene; these chemicals have been in use worldwide for many years and known environmental side effects are minimal if used according to the labels. McNaught et al (2014) showed that the baits had little effect on the local ant fauna and only one genus, Pheidole, was affected in a similar way to Red Imported Fire Ant. In addition, Pheidole spp.…”

“…Reasons for this variation relate to the knowledge gained by the programme in the previous 5 years on the efficacy of the baits (McNaught et al . ), the comparatively small area of infestation present at Yarwun and the general unsuitability of habitat for Red Imported Fire Ant. Because of safety considerations at the infested commercial properties, an additional round of treatment was applied in lieu of ground surveillance.…”

“…Nevertheless, in Queensland, McNaught et al . () have shown that repeated bait treatments with approved chemicals applied at appropriate intervals will eliminate both monogyne and polygyne populations of Red Imported Fire Ant.…”

Managing Risk and Increasing the Robustness of Invasive Species Eradication Programs

“…Repeated baiting is required to ensure that fire ant colonies are exposed to a sufficient level of pesticide over a sufficient duration for the colonies to die (McNaught et al. ). The high frequency of repeat treatments reflected uncertainty about the mortality of baiting in Australian conditions.…”