COFFEE LEAF SPOT IN PORTO RICO. 5 
Such results as have been obtained would indicate that the disease might 
be successfully combated by removing the diseased leaves. No doubt the de- 
foliation so produced is as bad for the tree as that caused by the fungus, 
but if the work were carefully done the newly formed leaves would remain free 
from infection, except as they might be gradually reached from trees outside 
the treated area. The fact that the disease spreads comparatively slowly and 
that the diseased leaves are readily recognized make this treatment more easily 
carried out. It would seem that this slow and apparently impracticable method 
might be really of value in combating the disease where the cheaper labor used 
on some of the plantations is available. 
Spraying with .Bordeaux mixture will exterminate the fungus if weather 
conditions happen to be favorable, but it is almost useless where the disease is 
most prevalent because of the frequent rains. The fungus can not infect leaves 
that are not moist much of the time; and when the leaves are dry, the time 
that Bordeaux would be most effective by adhering best, the disease is at a 
standstill, as any of the heads which happen to fall on such leaves do not 
germinate even if they adhere. The violent downpours soon wash the fungicide 
from the smooth upper surfaces of the leaves, where it must adhere to be of 
any effect. Moreover, the hillsides are so steep in many places that only 
knapsack sprayers could be used, and these only with difficulty. In case spray- 
ing is resorted to, it will be of most value when applied to the healthy trees 
near the diseased ones or to those less severely attacked, for the reason that 
the spray will prevent the infection of the leaves to which it adheres, though 
having no effect in preventing the formation of new propagative bodies on the 
already existing spots. 
It is of interest to note that, although the coffee plant is the principal host 
of this fungus, numerous other plants are also affected to some extent. The 
writer has found it on such unrelated host plants as the orange, mango, Begonia, 
various ferns, several of the coitres (Commelina spp.),and guava (Inga vera), 
and bejuco de carro (Velia sicyoides), and have noticed the spots, but not fruits, 
on the yautia, banana, and also on several wild plants.2 The coitres, which 
are perhaps most affected, and the ferns and other plants of low habit of 
growth form in many places a continuous ground covering and catch the 
greater part of the falling propagative bodies which escape the coffee leaves, 
and are hence peculiarly subject to the disease. They are apparently able to 
communicate it to unaffected plants of the same kind and doubtless also to 
healthy coffee plants. There were noticed places where the coffee was not 
attacked until several weeks after the ground plants had become infected. 
A STILBELLA-INFECTED PLANTATION. 
In 1916 the station was consulted in regard to a plantation which 
was said to have produced in former times betwen 300 and 400 
quintals of coffee. For some unknown reason, however, its produc- 
tion became considerably smaller until in some years it did not ex- 
ceed 10 or 12 quintals. A peon on the plantation reported the 1916 
crop as 48 quintals and the 1917 crop as 28 quintals. The plantation, 
which is located in the heart of the coffee country on the slopes of 
one of the highest peaks of the island, was visited by the writer and 
found to be in an almost abandoned state ; in fact, the condition was 
a Porto Rico Sta. Bui. 17 (1915), p. 13. 
52572°— 21 2 
