Laboratory evaluation of a boric acid liquid bait on colonies of Tapinoma melanocephalum Argentine ants and Pharaoh ants (Hymenoptera: Formicidae)

A 1% boric acid-sucrose water bait and 0.9% hydramethylnon granular bait were evaluated for efficacy against small laboratory colonies of Tapinoma melanocephalum (F.); Argentine ants, Linepithema humile (Mayr); and Pharaoh ants, Monomorium pharaonis (L.). T melanocephalum workers were reduced by 97% in the 1st wk and brood reduced by 96% in the 3rd wk when colonies were exposed to boric acid bait for as few as 3 d. The hydramethylnon bait did not significantly affect colony growth. L. humile colonies exposed to boric acid bait for 3 d resulted in reductions of 75 and 88% for workers and brood, respectively by the 3rd wk. L. humile colonies exposed continuously caused a 90% reduction of workers and brood by the 3rd wk. Workers and brood in colonies exposed to hydramethylnon bait were reduced 86 and 77%, respectively, after 3 wk. After exposure to boric acid bait for 3 d, M. pharaonis workers and brood were reduced 73 and 50%, respectively, by 8 wk. A continuous exposure of boric acid or hydramethylnon baits caused reductions of 90 and 60% for workers and brood, respectively, by 3 wk