The red flour beetle, Tribolium castaneum, is an important coleopteran pest of stored grain and cereal products. This study was aimed at screening on the extract of latexproducing plant for controlling T. castaneum based on their efficiency to alter the sugar metabolism by inhibiting trehalase activity and α-amylase activity. Four species of plants; Morus alba, Manihot esculenta, Ricinus communis and Carica papaya, have been extracted with methanol and were investigated for their bioinsecticidal effects and inhibitory activity against trehalase and α-amylase both in vivo and in vitro. Results showed that M. esculenta was the most toxic with 38.9% mortality after treatment. The duration of larval and pupal periods were extended by M. esculenta, R. communis and C. papaya. Adult emergence rate and the F1 progeny production were reduced by all plants. The methanol extract of all plants inhibited α-amylase activity both in vitro and in vivo. The trehalase activity was inhibited by M. alba extract in vitro, but all plants exhibited inhibitory activity against soluble trehalase after the extracts were incorporated into the diet whereas the membrane-bound trehalase activity was not interfered. The concentration of glucose decreased after treated with all extracts, but trehalose level was constant. At molecular level, M. alba, R. communis and C. papaya reduced the expression level of both Tcα-amylase and TcTrehalase-1 genes, but not TcTrehalase-2. Taken together these results suggest that these plants contained some compounds which affected the activity of α-amylase and trehalase enzyme at biochemical and molecular levels and consequently altered the level of glucose in red flour beetle.