Effects of trail pheromone purity, dose, and type of placement on recruiting European fire ants, Myrmica rubra, to food baits

Gerhard Gries, Danielle Hoefele, Jaime M Chalissery, Regine Gries

Abstract


Trail pheromones of ants guide nest mates to a food source. Applications of synthetic trail pheromone could guide ants to poisoned food baits, which may expedite the demise of nests and help control invasive ant species. The trail pheromone of the invasive European fire ant (EFA), Myrmica rubra Linnaeus (Hymenoptera: Formicidae), has previously been identified as 3-ethyl-2,5-dimethylpyrazine. To facilitate its development as an operational EFA control tactic, our objectives were to determine the effects of (1) pheromone purity (isometrically pure or isomeric mixture), (2) pheromone dose [2, 20, 200, 2,000 ant equivalents (AEs)], and (3) type of pheromone placement (pheromone encircling a food source rather than leading toward it) on ant recruitment to baits. In laboratory binary choice experiments, isomerically pure and impure trail pheromone prompted similar recruitment responses of ants. The presence of pheromone, irrespective of dose, enhanced the recruitment of ants to food baits, with the dose of 200 AEs eliciting the strongest recruitment responses (200 AEs: 69% of foraging ants, 20 AEs:  57%; 2000 AEs 59%). Pheromone applied in a line leading toward the food bait, but not in a circle surrounding a food bait, was effective in recruiting ants, suggesting that 3-ethyl-2,5-dimethylpyrazine has a guiding but not an attractive function to EFAs.


Keywords


Hymenoptera; Formicidae; trail pheromone; foraging behavior

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