The ability of plants to exhibit induced responses to herbivore damage is now widely recognized. It is not clearly known, however, how induced responses are elicited by and ultimately affect omnivores that feed both on herbivores and the plant itself. Previous studies have shown that plants can respond differentially to different species and even life-stages within a species. We don’t know if omnivory per se is also likely to evoke specific plant responses. For a plant hosting both an herbivore and its omnivorous natural enemy, there are numerous scenarios where specificity or lack thereof could substantially influence biological control. These ideas were explored with a mathematical model that generated specific testable predictions. We tested these predictions within the cotton agro-ecosystem through a series of laboratory and field experiments. The response of cotton seedlings challenged either by herbivorous mites or omnivorous thrips was evaluated through both bio- and biochemical assays. Our results suggest that cotton plants may not respond differently to herbivores and omnivores that produce the same type and amount of damage. This raises the possibility that an omnivorous natural enemy provides not only predation services, but also ‘immunization’ services to its host plant.