PORTO RICO EXPERIMENT STATION. 449 



of pedicles assumes a more or less spherical shape, becomes a harbor 

 for coccids, ants, cockroaches, etc., and is believed by many peons to 

 give rise to a "rust" disease of coffee growing beneath such shade 

 trees. Although coftVe does frequently die under Guanui trees badly 

 affected with the peduncle disease, no etiological connection has been 

 established between the two effects. The peduncle disease appears 

 to be of a physiological rather than of the '* witches broom" (Exoascus) 

 tj'pe. 



The Guaba {Inga vera), which is usualh' preferred for coffee shade, 

 appears to have no enemy other than the fungus mycelium which 

 sometimes attacks the roots of coffee and coffee shade trees in small 

 areas in old plantations. It is, however, much less prolific than its 

 related species, the Guama, producing but one light and irregular 

 crop of more or less imperfect fruits, instead of two heavy regular 

 (May and October) crops of seeds in an edible pulp. 



FUNGUS DISEASES. 



The following fungi have proved more or less injuritnis during the 

 year: 



CUid<)!i2>oriunt. eitrl, damaging sour stock in citrus nurseries. 



An undetermined '*spot" fungus appearing on the under side of 

 citrus leaves and resembling '"melanose;" this disease occurs com- 

 monly throughout central Mexico in the old orange groves. 



A red-spored "damping off" disease of citrus nursery stock in seed 

 beds. 



St'dhuiit jlavldu.tn on coffee at the coffee substation; not common. 



A root disease of coffee caused by the sul)terranean hypluv of an 

 undetei'mined fungus (Polyporus?). This disease spreads radially, 

 killing the shade trees and nearly all plants in its course, but its 

 progress is fortunateh' very slow. Ditching around the infected area 

 is advised. 



A red-spored fungus occurring in spots on the leaves of the Avo- 

 cado pear causes some damage locally. Practically all of the Avocado 

 pear trees in a district near Joyuda were reported to have died sinud- 

 taneously. The cause was not determined. 



GntpluoUi 2)Ii<itiu-lx is well estal)lished on the date palms of the 

 island. 



Cei'cospvra sp. occurs on Hedionda {Cam la occidental Is). 



Cercospor a per sonata injures peanuts {Arachis Kypoijxd). 



Cercosporium heticola is one of the four or more root rots of the 

 bean. 



Coleosporium iponuvR" appears in red-brown spots on sweet potato 

 leaves, but it is parasitized hy Ii< an ularia coleosjyoi'ii, \fh.\ch. appears 

 as a white dot in the center of the host colony. 



S. Doc. 148^ 58-2 2y 



