Insecticide formulations can be harmful to humans, livestock and pets due to both the active insecticide neurotoxin and also the inert ingredients used an adjuvant to deliver and apply the insecticide. While the toxicities of the adjuvant ingredients to non-target organisms are of noted concern and study, little has been reported regarding soil microorganisms. Here, we investigate the toxicity of insecticide adjuvant formulations to non-target soil bacteria. Five isolates of soil bacteria were characterized and identified to the genus level by 16S rDNA sequence analysis. Paper disks were impregnated separately with one of either six different insecticide formulations or matched concentrations (0.05%–50% active ingredient) of the pure pesticide found in that formulation and used in disk diffusion assays. All six formulations produced zones of inhibition ranging in diameter from 2.0 to 11.4 mm, with the exception of one formulation of the Serratia genus. However, disks impregnated with the same percentage of reagent grade insecticide showed no zones of inhibition under any condition tested. Growth curve analysis of the soil bacteria generations time shows that insecticide formulation containing 0.7, 7.0 and 70 μM of the active ingredient increased generation times in all isolates ranging from as much as 259%, 1032% and 1979% at volumes achieving active insecticide concentrations of 0.7, 7.0 and 70 μM respectively. Conversely, 120 μM malthione, bifenthrin, esfanvaletae, permethrin, deltamethrin and cypermethrin cause no change in the growth rate of all five bacterial isolates. Soil bacteria play an important role in maintaining healthy soil and providing microorganisms and plants with necessary nutrients and have an adverse effect on the food supply. A further and more careful analysis of the inert ingredients in pesticide formulations needs to be performed as these substances are not only directly toxic to humans but also threaten the food chain and food quality.