Repellency and toxicity of mint oil granules to red imported fire ants (Hymenoptera: Formicidae)

Repellency and toxicity of 2% mint oil granules were evaluated against worker red imported fire ants, Solenopsis invicta Buren, in a series of laboratory and field experiments. In continuous exposure experiments, LT50 values ranged from 1.2 h with 164.8 mg/cm(2) of 2% mint oil granules to 13.3 h with 1.65 mg/cm(2) of granules. LT50 values declined exponentially with increasing rate of mint oil granules. Limited exposure to 164.8 mg/cm(2) mint oil granules resulted in >50% knock down (KD) after 30 min; however, there was no KD at 15 min. Twenty-four hour mortality increased linearly with increasing exposure time. Mean repellency of worker red imported fire ants ranged front 49.2) +/- 5.4% for 0 mg/cm(2) (untreated control) of mint oil granules at 30 min to 100% for 147.8 mg/cm(2) of mint oil granules at 3 h. Repellency increased with increasing milligrams per S(square centimeter of mint oil granules and exposure time. In field tests, 100% of mounds opened and treated with mint oil granules were abandoned 5 d after treatment and ants had relocated or formed satellite Mounds by 2 d after treatment. Unopened mounds treated topically with mint oil granules were not abandoned, but ants formed satellite mounds 2 d after treatment. Mint oil granules could provide another tool for red imported fire ant integrated pest management, particularly in situations in which conventional insecticides Would be inappropriate.