One of the most important soilborne diseases affecting avocado (Persea americana Mill.) crops is white root rot, caused by the fungus Rosellinia necatrix. In this study we investigated the metabolic responses elicited by white root rot in the aerial part of the plant with special focus on the potential applications of imaging technique (including chlorophyll fluorescence (Chl-F), blue-green fluorescence and thermography) in early detection of the disease on leaves. The results show that leaf metabolism was significantly affected by the infection only when symptoms started to appear, which was probably related to the loss of root functionality. However, changes in some Chl-F parameters provided early indications of stress even prior to the development of symptoms. We suggest that the combinatorial analysis of several Chl-F parameters could be used as a method for early detection of stress related to white root rot, and might prove useful as a general indicator of biotic and abiotic stress in avocado plants.