TRIFLUMURON AND IMIDACLOPRID BAITS EVALUATED AGAINST FIELD COLONIES OF COASTAL BROWN ANTS (PHEIDOLE MEGACEPHALA)

Abstract:
The Coastal Brown Ant (Pheidole megacephala) is a major introduced nuisance pest species in the most populated regions of Australia. The aim of this trial was to examine the potential of imidacloprid and triflumuron as active ingredients for ant baits. Baits based on peanut butter and the nitromethylene insecticide lmidacloprid and the chitin synthesis inhibitor Triflumuron were fed to nests of Pheidole megacephala for about 12 months. Commercially available Hydramethylnon ant bait stations were used for comparison. A method is described in which the active ingredients are mixed into peanut butter and placed in weather-proof bait stations. Assessment of nest activity used visual assessment of ant activity along with the daily consumption rates of untreated peanut butter monitoring baits. The method proved effective but it is essential that more than one parameter is measured in order to establish whether nests are eradicated or merely foraging elsewhere. Imidacloprid formulated in peanut butter was not found to be efficacious against Pheidole megacephala due to its rapid action and associated a 'bait shyness' for doses above 0.002%. Any initial effect on the colony at 0.0005% disappeared over the following months. Triflumuron was effective at 3% but baiting must continue for many months, even a year. This is possibly due to the longevity of the worker ants. Eradication from areas may require a wide area baiting campaign because other colonies invade the areas made vacant by the elimination of the primary nest. Commercially available Hydramethylnon baits were not readily eaten by ants. Visible ant activity declined within 2-3 months of starting baiting however placement of untreated peanut butter baits at the site of the previously active entrance site, resulted in large numbers of ants appearing and the consumption of bait quantities similar to consumption at untreated controls. Hydramethylnon bait stations are therefore considered to be insufficiently efficacious against Pheidole megacephala.