Perimeter treatments with two bait formulations of pyriproxyfen for control of Pharaoh ants (Hymenoptera: Formicidae)

Abstract

Pyriproxyfen, a juvenile hormone analog, was formulated into 2 types of baits and applied to the exterior of buildings for control of natural infestations of the Pharaoh ant, Monomorium pharaonis (L.). Pyriproxyfen baits were formulated at 0.5 and 1% by weight in an unprocessed peanut oil attractant applied to a pregel defatted corn grit carrier and at 0.25% in a composite bait consisting of unknown ingredients. Both baits effectively controlled the ants. Worker numbers were reduced between 84.5 and 94.3% at 2.5 wk after the 2nd bait application when the 0.25% pyriproxyfen composite bait was applied to apartment buildings with separate apartments. Outdoor worker numbers were reduced 84% 2 wk after the 2nd bait application when 0.5% pyriproxyfen bait was applied to a large building with separate wings. A reduction of >85% in worker number was not observed in the 1% pyriproxyfen treatment until 8 wk after the 2nd bait application; however, no ants were ever found indoors in this treatment. Dyes in the pyriproxyfen oil treatments were used to determine if ants foraged from one treatment area to the next. Calco oil dyes used as markers in the oil bait were detectable in the postpharyngeal gland of the queens and workers for up to 14 wk after baiting in the field and 17 wk after baiting in the laboratory. A perimeter treatment applied to large buildings with separate wings was more difficult to evaluate than treatments applied to separate buildings containing multiple apartments because contaminated ants from treated areas, as indicated by the presence of dye, were found in the controls.