Management Notes for this Location:
A case-study of little fire ant control in Tahiti on a very small urban infested area (0.3 ha) by a pest control company.
In Te Tavake residence, the infested area was approximately 100m by 30m and sloping. The owners association engaged the services of a pest control company (at a cost of cost of USD 1,300). They used Propoxur first, followed by a second pass some days later to spread Amdro. Post treatment monitoring showed that all contaminated areas were cleared except for an area of about 5m x 5m within one lot (Loeve, E., pers. comm., October 2005).
However, serious concerns have been raised about this eradication effort, especially about the use of the highly toxic Propoxur and potential waste of money. This highly toxic chemical will not kill ants in the nests (which is what is required) unless directly applied in a drench form to individual nests. It will kill the foraging ants and drive the remaining survivors underground. The subsequent use of Amdro is highly likely to have been a waste of money, as there are unlikely to have been any foragers out gathering food to take the bait back to the nest. As Amdro is relatively non toxic and with a short half life, it is unlikely to have achieved the desired result. In conclusion, Amdro is highly recommended for control of W.
auropunctata, but not following the application of the knockdown chemcial Propoxur. As Amdro relies completely on the foraging activity of workers to transfer toxic bait back to the nest, the Propoxur will have removed the foragers from the ground, thereby negating any effect of the Amdro (O'Connor, S.,pers. comm., November 2005).
In fact, a September 2006 assessment, conducted one year after the treatment, showed that while the colony had been substantially weakened, little fire ants were still present in large numbers in the contaminated areas (Loeve, E., pers. comm., September 2006). The lesson learned here is that even with localised appropriate ground treatments using toxic baits, there will invariably be some survivors. To minimise the number of survivors it is advisable to incorporate a treatment buffer zone around known infested areas. This will reduce the likelihood of previously undetected populations missing out on a toxic dose of bait. Additionally, frequent post treatment monitoring will allow timely detection of any surviving populations. High density monitoring using attractant baits at 1 month, 3 months, 6 months is strongly recommended. Any detected surviving nests should be mapped and allowed to increase in numbers to facilitate high recruitment rates to any subsequently applied toxic bait, but do not allow numbers to increase to the point where arboreal nesting commences. Unless frequent post treatment monitoring occurs, it is almost guaranteed that there will be patchy remnants of the infestation, regardless of treatment. The probability of ants surviving treatment is highly variable and depends on the product used, its application rate and method, environmental conditions, microhabitats available to the ants, and whether or not arboreal nests exist (O'Connor, S., pers. comm., November 2006).
Experience suggests that 1m grid surveys must be conducted in order to be sure that all ants have been eradicated. In addition, it is necessary to wait up to 6 months to have an accurate assessment of success, as remnant ant populations can be very low and hard to detect (Hoffmann, B., pers.
comm., October 2005). General consensus is that to be sure that eradication has been achieved in a treatment area, there should be 2 years monitoring with no ants found during that period (O'Connor, S., pers. comm., November 2006). Advice is available (in French) on Detecting and Reporting Wasmannia auropunctata from Fenua Animalia.
