Foliar nutrients and secondary metabolites may affect the immunocompetence of herbivorous insects against biological control agents. Dietary levels of specific essential vitamins, such as ascorbate, and micronutrients, such as Se, influence a key fitness trait of Heliothis virescens larvae: immunocompetence against baculoviral infection. Development of more sensitive biomarkers of immune response against biological control agents would speed the analysis of immunomodulatory phytochemicals. Therefore our near-term objective was the identification of plasma proteins involved in the host immune response against entomopathogens and parasitoids (the immunoproteome). Plasma prepared from bacterially infected larvae and from larvae parasitized by the ectoparasitic eulophid wasp Euplectrus comstockii were labeled with Cy3, and compared with Cy5-labeled plasma from naïve larvae by DIGE (2D Digital Gel Electrophoresis). Induced (green-shifted) and repressed (red-shifted) host plasma proteins were picked from gels and subjected to MALDI-TOF peptide sequencing to facilitate identification, isolation, and further analyses of the H. virescens plasma immunoproteome.