Leaves of tomato plants were wounded with scissors and then treated with Helicoverpa zea (tomato fruit worm)labial salivary gland extracts, autoclaved salivary extracts, leucine amino peptidase (LAP) purifed from caterpillar salivary glands or water. Four days later the tomato leaves were measured for anti-herbivore defenses such as trypsin inhibitor and polyphenol oxidase. Tomato plants wounded and treated with purified LAP had significantly higher levels of trypsin inhibitor and polyphenol oxidase. In addition caterpillars that fed on leaves treated with LAP had signifcantly the lowest body weights. A microarray was then performed to determine gene expression in tomatoes in response to labial salivary extract.