We focused our study on the effects of Larrea cuneifolia phenolic resin on leaf-cutting ants from two populations (Sierra de las Quijadas National Park and San Roque) of Acromyrmex lobicornis in San Luis, Argentina. We conducted two bioassays of food choice (field and laboratory) to compare the effects of phenolic resin on ant workers from these two populations. Results of the field experiment indicated that there were no differences in preference for either leaves treated with resin or untreated leaves among colonies from both localities. However, results of the laboratory experiments with individual ants indicated a significant effect of population and treatment on the time spent in different treatments. While leaf-cutting individual workers from Quijadas preferred the phenolic resin, workers from San Roque avoided it. These results evidence that ants respond according to time of exposure to chemicals from plants (presence or absence) and that the effects of resin among a population can be observed and measured on individual ant workers, even in the absence of fungus garden influences in the nest.