Diseases are one of the most serious threats for citrus production worldwide. Sao Paulo, Brazil and Florida, USA, are the most important citrus producers and, both, are making efforts for citrus diseases control. Citrus canker is one of the serious diseases, caused by the Xanthomonas citri subsp. citri bacteria, that infects citrus trees and relatives, causing a large economic loss in the citrus juice production. Another important disease affecting the citrus production worldwide is the Huanglongbing (HLB, Greening), present too in Sao Paulo and Florida. Both bacterial pathogens are, mainly, under suppression control, applied by eradication of symptomatic and no-symptomatic plants. In this way, the detection and diagnostic of the related symptoms and, consequently, the eradication of the citrus trees are essential for higher economical losses prevention. However this task is very hard and it is done by: a) A field detection, made by naked eye inspection of each citrus three; and b) the laboratory diagnostic. In this way, our goal is to develop a new optical technique, applied in field conditions, to detect citrus diseases using a portable fluorescence imaging unit.

Our system is composed of: i) Several high power light emitting diodes at 365, 405, 470 and 530 nm; ii) One motorized filter wheel with different interference transmission filters at 690 and 740 nm; iii) Imaging optics and a CCD camera. This system allows us to perform image of the chlorophyll fluorescence in the whole leaf. We have obtained fluorescence images of citrus leaves contaminated with Citrus canker, Citrus Scab, Citrus Variegates Chlorosis and Huanglongbing. For each disease, we have collect images of one hundred different leaves from field orchards. This procedure reduces the detachment time effect on the fluorescence. At the moment, we are carrying out different image analysis to try to discriminate between these four diseases.