Toxicity of a boric acid-sucrose water bait to Solenopsis invicta (Hymenoptera: Formicidae)

Boric acid-sucrose water baits were evaluated in the laboratory for toxicity, consumption, and efficacy against the red imported fire ant, Solenopsis invicta Buren. Over the dosage range from 0.02 to 1.0% boric acid, LC50s (95% CL) ranged from 1.27% (1.05-3.88%) at 3 d to 0.11% (0.09-13%) at 8 d. Amount of bait consumed was related inversely to the concentration of active ingredient. High concentrations of boric acid bait (5%) were consumed at a lower rate than the control (10% sucrose water). In large fire ant colonies exposed continuously to 4 concentrations (0.25, 0.5, 0.75, 1.0%) of boric acid bait, workers and brood were reduced by 90% at 6 wk. Therefore, low concentrations of boric acid are necessary for delayed toxicity and reduced repellency