Many insect natural enemies are omnivorous, in that they include extra-floral nectar, floral nectar, honeydew and pollen, as well their insect prey in their diet for at least part of their life. Access to these plant-based foods can reduce pest pressure by increasing both the individual 'performance' and local density of natural enemies. Commercial 'food sprays' that are rich in carbohydrates and proteins, such as Amino-Feed and Envirofeast, can be applied to cotton crops to act as artificial plant-based foods. *We examine the extent to which Amino-Feed and Amino-Feed UV benefit a predator, the Pacific damsel bug, and a pupal parasitoid, the banded caterpillar parasite. These insects are important natural enemies of heliothis. *The provision of either wet or dry residues of Amino-Feed UV had no discernible effect on Pacific damsel bug survival and development rates. *In contrast, the provision of artificial nectar, cotton extrafloral nectar and Amino-Feed (plus extrafloral nectar) had a marked effect on banded caterpillar parasite longevity. Whilst fed female parasitoids lived longer, the total number of eggs they laid was unaffected by diet. This is because females exhausted their maximum egg supply around the same time across all treatments, and death occurred shortly thereafter in the water control treatment but after considerably longer in the other diets. Because females of the banded caterpillar parasite were also able to feed on small amounts of host body fluid, this alternative source of nutrition best explains why there was no effect of diet on fecundity (i.e., the number of eggs laid). *It is likely that providing natural enemies with a supplementary source of food will be more important during periods of prey/host scarcity or absence. Thus, from the perspective of integrated pest management, artificial and natural plant-based foods are worthy of further investigation because they have potential to improve the ecosystem service of biological pest control.