Energy dispersion X-ray fluorescence technique (EDXRF) was employed to study the effects of the fumagina disease through the elementary chemical composition of leaves. The experimental setup consisted of a Mo X-ray tube (Kµ=17.44 keV) with Zr filter and a Si(Li) detector. The measurements were performed with infected and healthy leaves of citric plants. The elements Ti, Mn, Fe, Cu and Zn were quantified. For all the elements of interest the measured detection limit was at the order of mg . g-1.