The objective of this project was to evaluate an IPM approach to fire ant control using multiple biological control agents supplemented by a chemical treatment.
RESULTS AND DISCUSSION
Three years after initial treatment, the results in Figure 3 indicate that: a) in Site C (untreated control), fire ant populations increased by 7%, however, during the study, increases as high as 83% occurred; b) in Site B (chemical only treatment), the fire ant population decreased by 80%, and 72 weeks after the initial treatment, the fire ant control dropped below a preestablished 90% threshold. Under normal circumstances, at this point, retreatment would have been necessary; c) in Site A (IPM), there was 95% reduction in fire ant colonies in the final evaluation. In several evaluations during the study, the reduction was 97% or greater. These results indicate that the IPM approach using a single chemical treatment in conjunction with the two biological control agents controlled fire ants for a longer period without the need for retreatments.
In addition, in the IPM treatment area (Site A), the native ant populations increased while the fire ant populations continued to decrease (Figure 4). The native ant populations remained low in all other sites and did not replace fire ant populations.
Figure 5 shows the mean T. solenopsae
infection rates for plots in the different areas. A high infection rate occurred in the IPM untreated area of Site A, while the infection rate in the IPM fipronil-treated area was much lower because there were very few colonies remaining. T. solenopsae
was also detected in Site B (fipronil-treated area) thus the pathogen spread to this site even though it was never applied here.
Figure 6 shows the actual spread in the IPM area (Site A) of the pathogen, T. solenopsae
, in fire ant colonies (yellow dots). At this site, 138 of the 175 (79%) colonies were infected in September 2002, as opposed to only 30% observed in May 2002. It also demonstrates detection of T. solenopsae
in the chemical treatment site, with 35 of the 160 (22%) colonies infected in September 2002 compared to 4 of the 66 (6%) colonies in May 2002. The pathogen may have been accidentally transferred to this site during our surveys, but the fact that this organism is so easily spread is encouraging. The decapitating flies also spread and were found attacking fire ant workers within an area up to three miles around the initial release site. In conclusion, these results are a good indication that it is possible to use an IPM approach for the control of fire ants when the right tools and conditions are available.