Submitted to: Insect Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/10/2009
Publication Date: 11/11/2009
Citation: Chen, J., Shang, H., Jin, X. 2009. Response of Solenopsis invicta (Hymenoptera: Formicidae) to potassium oleate water solution. Insect Science. 17:121-128. Interpretive Summary: Contact insecticides are frequently used in the red imported fire ant quarantine and management, which is an important source of the pesticide contamination in the environment. A fatty acid from soap was found to quickly knockdown fire ants. Combinations of the fatty acids with other non-insecticide materials, such as fire ant repellants could improve fire ant quarantine treatments and lead to a more environmentally friendly technology for fire ant quarantine. Incorporating fatty acid into individual mound treatment formulations may also improve their effectiveness.
Technical Abstract: The knockdown, mortality and digging behavior suppression of red imported fire ant adults, Solenopsis invicta Buren, by potassium oleate (PO) water solutions were examined. PO at concentrations of 0.03125%, 0.0625%, 0.125%, 0.25%, 0.50%, and 1.00% (w/w) was used in a knockdown bioassay, 0.03125% in a mortality bioassay, and 0.25%, 0.50% and 1.00% in a digging bioassay. Ants could not float on the surface of the PO solution as they did on the surface of the distilled water. They were immediately submerged after being placed in the PO water solution, which led to a quick knockdown. The time needed to knockdown worker ants (Tk) was always positively correlated with their body weight. Tk ranged from 42.40 ± 1.46 s to 85.30 ± 23.63 s for major workers, 33.55 ± 1.12 s to 49.15 ± 5.46 s for minor workers, 72.65 ± 5.85 s to 84.35 ± 6.26 s for male alates, and 98.80 ± 12.86 s to 627.85 ± 54.21 s for female alates. In most cases, Tk for the major workers was significantly greater than that for the minor workers. Although mortality did occur in one colony after worker ants had been submerged in 0.03125% PO water solution for just 10 min, some workers could still recover from knockdown after being submerged in PO solution for up to 640 min in one tested colony. LT50s for 0.03125% PO water solution at 25 °C were calculated to range from 139.58 to 307.47 min for major workers and 66.40 to 166.29 min for minor workers. PO at concentrations of 0.25%, 0.50% and 1.00% significantly suppressed the digging behavior of workers from all three tested colonies except one colony at 0.25%.