The fall armyworm, Hyphantria cunea Drury (Lepidoptera: Arctiidae) is an insect native to North America that was recently introduced into Iran resulting in severe damage to trees and agricultural production. An experiment was conducted to examine potential effects of medicinal plants, Artemisia annua and Lavandula stoechas and the insect pathogenic bacterium Bacillus thuringiensis var. kurstaki on activities of digestive enzymes (α-amylase, α- and β-glucosidase, lipase and proteases) and lactate dehydrogenase (LDH) in H. cunea by using two hosts, mulberry and sycamore. Results showed that B. thuringiensis var. kurstaki and plant extracts when administered orally, affected the digestive enzyme profiles of H. cunea. Combined effect of B. thuringiensis, A. annua and L. stoechas extracts on mulberry decreased the activities of digestive enzymes in a dose-related manner, except for β-glucosidase and lipase. When larvae were treated by different concentrations of the mentioned insecticides, LDH activity increased i.e. the higher activity was obtained by B. thurengiensis alone and B. thurengiensis and L. stoechas extracts together. The least activity was observed in the case of L. stoechas extracts alone on both hosts. Physiological analysis would be particularly informative when using combination of biopesticides to enhance the efficiency of a safe management process.