Plant natural compounds dibromothymoquinone, juglone, lapachol, plumbagin, 1-naphthoquinoline, dichlon, napthazarin, thymoquinone, benzoquinone, and á-naphthoquinone were tested against aphids and two-spotted spider mites in laboratory bioassays. Green peach aphids, Myzus persicae and mites, Tetranychus urticae were introduced on leaf discs treated with different concentrations of the test compounds in Petri dishes. Mortality was determined after 48 hours. Plumbagin was the most effective against mites (LC 50=0.001%) and Dichlon the least effective. Both plumbagin and dibromothymoquinone were the most effective against aphids (LC 50=0.03%). Our results indicate some structure function relationships useful in designing new insect control agents for agriculture