Communication disruption of red imported fire ants (Hymenoptera: Formicidae) and reduced foraging success

Invasive pest ants often coordinate resource retrieval and colony expansion through the use of recruitment pheromones to optimise their foraging; the potential for disruption of trail pheromone communication deserves investigation as a new biologically-based method to control pest ant species. Workers from monogyne red imported fire ant colonies following trails to feed on crickets were presented greater than normal quantities of their orientation trail pheromone, Z,E-α-farnesene. The pheromone was presented as either a 300 μg point source or a linear source at 5.5 μg / cm. Ant behaviour was video recorded from above and digitised. Ants following a 10 ng / cm synthetic trail of Z,E-α-farnesene past an upwind source of the same synthetic trail pheromone took 2.4-fold (single release points) or three-fold (linear source) longer to discover the bait and remove it than ants following trails in the absence of pheromone treatments. About half (48%) of the fire ants that went past the linear sources of trail pheromone were prevented from arrival at the food compared with untreated controls (100% arrival), and ant trails had significantly lower trail integrity, measured as r² (obtained by linear regression), both towards the food and when returning to the nest. The less than complete drop in arrival was likely due to the ability of the ants to recover their normal ability to sense and follow the recruitment trail in clean air. A few ants were able to follow low concentration synthetic trails despite exposure seconds earlier to a 550- fold greater concentration of pheromone, which disrupted trail following behaviour. Trail pheromone disruption of fire ants has potential for fire ant population reduction if low cost commercially available disruptants become available. Structure-activity studies and biorational design of suitable analogues / homologues that overcome trail pheromone sensitivity would be a next step.