Four epoxide hydrolase genes, 'NbEH1.1, NbEH1.2, NbEH2.1' and 'NbEH2.2,' were amplified from 'N. benthamiana' infected with the hemibiotrophs, 'C. destructivum, C. orbiculare' or 'P. syringae' pv. 'tabaci,' or undergoing the hypersensitive response (HR) to 'P. syringae' pv. ' tabaci' ('avrPto'). 'NbEH1.1' and ' NbEH2.1' showed the greatest changes in expression, and 'NbEH1.1 ' and 'NbEH2.1' expression was generally higher during necrotrophy and biotrophy, respectively. For HR, only 'NbEH1.1 ' expression increased. Virus-induced gene silencing of 'NbEH1.1 ' and 'NbEH2.1' lengthened the biotrophic phase of ' C. destructivum' but not for 'C. orbiculare. NbEH1.1' silencing reduced populations of 'P. syringae' pv. ' tabaci,' but HR was not affected by silencing either gene. Epoxide hydrolase genes differentially respond to pathogen attack and play an important role in plant defenses. To measure fungal infection of leaves, an image analysis program was adapted to quantify 'C. destructivum' infections of 'N. benthamiana' as well as anthracnose, rust, powdery mildew and scab diseases.