Mortality of Ant (Hymenoptera: Formicidae) Pest Species Exposed to Sodium Hydrogen Carbonate
AbstractLaboratory bioassays enabled us to determine the mortality of Argentine ant (Linepithema humile [Mayr]) workers, and red imported fire ant (Solenopsis invicta Buren) workers exposed to sodium hydrogen carbonate (NaHCO3, sodium bicarbonate). The median lethal concentration (LC50) of NaHCO3 for Argentine ants was 5.64 mg per cm2 after 5 d exposure and 3.96 mg per cm2 after 6 d. Cumulative mortality for Argentine ants exposed to 28 mg NaHCO3 per cm2 was 89.5% on day 6. Workers of both species were exposed to concentrations of 9.92, 17.70, or 152.00 mg NaHCO3 per cm2 in separate tests. Mortality of Argentine ants was significantly higher than that of fire ants following exposure to 9.92 mg NaHCO3 per cm2, while mortality for the two species did not differ following exposure to the two higher concentrations. Mortality of both species treated with the highest concentration exceeded 99% at 6 d. In tests with equivalent amounts of sodium in NaHCO3 and NaCl treatments, mortality for fire ants exposed to NaHCO3 was about 46% after 6 d. Mortality for fire ants exposed to NaCl was about 15% and was similar to that for untreated ants. Argentine ants were provided sugar water baits containing a range of NaHCO3 concentrations. Argentine ant mortality after 6 d exposure to 5% NaHCO3-sugar water treatment was about 50%. Mortality was not higher for workers exposed to higher concentrations of NaHCO3 in sugar water baits. Enzymatic dysfunction caused by unfavorable increases in internal pH is the most likely explanation for worker mortality following exposure to NaHCO3.
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