a very serious oltstaele to the suecessful eulture of the ehayote. All' 

 of our collections of leaf spot on this host have been of this latter 

 type, pyenidia of Phijllosficta being found in only one very old spot, 

 making it appear probable that the Phyllosticta is but secondary 

 when present at all. 



A root rot has lieen reported by some growers, but no data iias 

 ])een secured. 



Corn {Zea mays). 



Both the rust and smut were observed, the latter less commonly. 

 The rust Vredo paUi'la Diet and Holw.) attacked the older and lower- 

 leaves, generally at a time when the ears were nearly mature so that 

 little damage could be attributed to it. It appeared as numerous 

 small b]'own pustules on the under side of the leaves. 



The smut (Ustilago zeae [Beck] Ung.) attacked all parts of the 

 plant, distorting or destroying them, and forming irregular masses 

 covered by a white membrane, which broke away, liberating the black, 

 powdery, spore mass. It is of no importance in Porto Rico as yet. 



A third disease occurred quite commonly, but is of no economic 

 importance as yet. This is manifested as numerous black, carbonous 

 slightly raised spots on the leaves (both surfaces) and leaf sheaths 

 in which tlie spore-bearing bodies are produced. Each spot is sur- 

 rounded ])y a yellow or brown circle of dead tissue. The death of 

 old or basal leaves is hastened, especially when the rust is also present 

 as is usually the case. The fungus is Phylhiclioro (/rauiinis (Pers.) 

 Fuekel. 



CowPEA {Vigua unguiculnia). 



This legume has been used in some gardens between crops to- 

 improve the soil. Certain varieties thrive very well and th.-ir in- 

 creased use is reconnnended. The iron variety is especially good for 

 growing in this connection since it is not sul).i('ct to nematodes, and 

 in so far as observed does well under Porto Rican conditions, (^ther 

 varieties are cultivated to some extent under tlie name of "'frijoles"' 

 as food plants. INIost of these latter types are. however, very subject 

 to root-knot and proper precautions must hv taken to avoid this 

 trouble. 



Leaf Spot (Cercospora vigna^- Racib.) — Tliis leaf spot as men- 

 tioned in a previous report (10) caused defoliation of an unknown 

 variety of cowpea (not tlie iron) grown at tbi- Station. The spots 

 Avere numerous, circular, up to one centimeter in diameter, reddish 

 brown in color, with distinct margins, and soon <'onfluent. causing- 

 tlie death of the leaf. 



100 



