THE COFFEE LEAF SPOT (STILBELLA FLAVIDA) 
IN PORTO RICO. 
CONTENTS. 
Page. 
Introduction 3 
The leaf spot and what it does 3 
A Stilbella-infected plantation 5 
Cleaning out a diseased section 6 
Page. 
Numerous hosts 7 
Observations subsequent to clearing 8 
Recommendations for eradicating 
Stilbella 11 
INTRODUCTION. 
The purpose of this bulletin is to indicate means of controlling in 
the plantations of Porto Rico the coffee leaf spot {Stilbella flavida) 
(PL I), which is the cause of heavy and continuous losses to the 
coffee growers in Porto Rico, few of whom know anything of its 
nature, or are able to distinguish it from any other spotting of the 
leaves. The suggestions given for combating the disease are so 
simple that it is believed they may be easily carried out by any 
planter. There are many abandoned coffee lands in Porto Rico that 
doubtless can again be made to produce at a profit if the grower will 
follow the method outlined. The work required can be done, too, at 
a minimum cost and with very little effort. Many of the ravaged 
lands are not adapted to any other money crop at present, and, while 
the coffee industry is not in flourishing condition in Porto Rico, it is 
the most promising one for certain areas. 
THE LEAF SPOT AND WHAT IT DOES. 
The climatic conditions which seem most favorable for the growth 
of the coffee tree (Coffea arabka) also foster the development of the 
coffee leaf spot disease. 
The disease is described in part by Fawcett x as follows : 
In Porto Rico it is found principally in the higher altitudes, where it is 
favored by excessive rainfall. Lower down it is found near streams and where 
it is sheltered from winds and afforded a moist atmosphere during part of the 
year. It is more dependent on moisture than other coffee fungi, being unable to 
infect new leaves or to form new fruits except under conditions of extreme 
humidity. 
1 Porto Rico Sta. Bui. 17 (1915), p. 11. 
52572°— 21 Q 
