Candidatus Liberibacter asiaticus (Las) has been reported to increase the susceptibility of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), to selected insecticides. Reduced general esterase activity in Las-infected, compared with uninfected, D. citri has been proposed as a possible explanation for this difference in insecticide susceptibility. The current study was conducted to quantify glutathione transferase (GST) and cytochrome P₄₅₀ (general oxidase) activities in Las-infected D. citri to further explain the possible mechanisms for altered susceptibility to insecticides due to Las infection. GST and cytochrome P₄₅₀ activities (indirectly through general oxidase levels) were quantified in Las-infected and uninfected D. citri nymphs and adults. Mean (±SEM) GST activity was significantly lower in Las-infected (468.23 ± 26.87 /µmol/min/mg protein) than uninfected (757.63 ± 59.46 µmol/min/mg protein) D. citri adults. Likewise, mean cytochrome P₄₅₀ activity was significantly lower in Las-infected (0.23 ± 0.02 equivalent units [EU] cytochrome P₄₅₀/mg protein) than uninfected (0.49 ± 0.05 EU cytochrome P₄₅₀/mg protein) D. citri adults. Immature stages (second and fifth instars) were characterized by significantly lower GST activity than adults for uninfected D. citri. However, cytochrome P₄₅₀ activity was significantly higher in second instar nymphs than adults and fifth-instar nymphs for uninfected D. citri. Lower activities of GST and general oxidase in Las-infected D. citri indicate that infection with Las alters D. citri physiology in a manner that could increase insecticide susceptibility. The reduced activities of these detoxifying enzymes due to Las infection may be explained by examining expression levels of associated genes in Las-infected and uninfected D. citri.