APHIS expanded the regulated area in South Florida for Citrus Black Spot (Guignardia citricarpa) effective March 31, 2015. Citrus Black Spot is a fungal disease marked by dark, speckled spots or blotches on the rinds of fruit. Citrus Black Spot is an economically significant citrus disease. The disease is spread through spores released from fallen, decomposing citrus leaves.

While all commercial citrus cultivars are susceptible to citrus black spot, the most vulnerable are lemon and late-maturing citrus varieties like Valencia.
Click on the image below for more information..
References:
Save Our Citrus. http://www.saveourcitrus.org/index.php/citrus-black-spot