96 JOURNAL OF AGRICULTURE OF P. R. 



BLACK MELANOSE OR GREASY SPOT. 



This almost universally present spotting of the leaves is known 

 to many of the growers as melanose, and hence much confusion has 

 resulted. Greasy spot is a common disease in Cuba and the Isle 

 of Pines, but is less prevalent in Florida. Grapefruit leaves are 

 especially subject to it, although it can be found on practically any 

 citrus species. 



It is characterized by generally numerous, somewhat irregular 

 areas, occurring on both leaf surfaces, but more prominently on 

 the upper, and varying from an eighth to a quarter of an inch in 

 diameter. The markings are only slightly raised, and vary in color 

 from a light yellow or mere translucenee of the tissues through vari- 

 ous shades of brown to a very deep brown or black. In the younger 

 stages there is a greasy appearance, suggesting the name. Tliey 

 can easily be distinguislied from melanose markings by the larger 

 size and the fact that tliey are very slightly, if any, raised. 



Trees of all ages and in all conditions of health and disea.se are 

 apparently subject to this phenomenon, and although no fungi or 

 other organisms have been found associated with it, indications point 

 rather decidedly to parasitic origin. Inasmuch as no appreciable 

 damage is caused, affected leaves falling very little if any sooner 

 than normal ones, control measures are not considered necessary. 



STELLATE MELANOSE. 



Certain peculiar markings, given the name of stellate melanose, 

 have been found on grapefruit leaves, but never to such an extent, 

 as to be causing damage. These markings, which occur on eithei* 

 side of the leaf, though more commonly above, may be few or many, 

 and in their raised character and color are similar to melanose mark- 

 ings. They are, however, much more extensive, often from four 

 to eight millimeters across, and irregular to stellate in shape. An 

 especial characteristic is the longitudinal splitting of the branches 

 of the individual spots. 



The cause is not known. It is interesting to note in this connec- 

 tion that this spotting has been found in but three groves, and in 

 each case following Bordeaux spraying. Orange trees and unsprayed 

 grapefruit in the same groves were free of the Tuarkings. 



ALGAL LEAF SPOT (Cephaleuros virescens). 



The lime is especially subject to this leaf spot, to such an ex- 

 tent, in fact, that it almost serves as a distinguishing characteristic 



