Low Concentration of Azadirachtin Has the Same Toxic Effect as Imidacloprid + Lambda-Cyhalothrin in Workers of Two Species of Leaf-Cutter Ants1

Leaf-cutter ants of the genus Atta are pests controlled by broad-spectrum insecticides that adversely affect the environment and human health. Toxicity of 20 concentrations of chemical imidacloprid + λ-cyhalothrin and biological insecticides azadirachtin and spinetoram were evaluated on workers of A. mexicana and A. cephalotes ants. Initial evaluation determined optimal concentrations to kill 10-90%. Mean lethal concentrations of imidacloprid and azadirachtin were determined, and mean lethal times were through 3 × 10-1 µl/liter concentration of each insecticide. Azadirachtin and imidacloprid + λ-cyhalothrin at 3 × 10-1 µl/liter concentration killed 100% of both species. LC50 values of imidacloprid + λ-cyhalothrin and azadirachtin were similar against both species. But, the TL50 of imidacloprid + λ-cyhalothrin was less (28-29 hours) in both species compared to the TL50 by azadirachtin that was 36 to 41 hours. Insecticide based on extracts of neem (azadirachtin) was as toxic as imidacloprid + λ-cyhalothrin against A. mexicana and A. cephalotes worker ants. Azadirachtin is an environmentally friendly alternative to manage the two ant species, and probably other species of Atta and other ant pests.