14 



never causes the fleshy part of the berry to adhere to the parchment, 

 in this way making the pulping more difficult. Out of several lots of 

 berries examined, of which all were affected by Stilbella, a varying 

 nimiber, from 6 to 18 per cent, were so badly affected that the dis- 

 coloration could not be removed in the process of polishing to which 

 coffee is subjected in preparation for the market. 



An experiment in the control of this disease, was begun at the sub- 

 station, La Carmelita, to test the efficiency of gathering and destroy- 

 ing the diseased leaves, a method recommended in some publications 

 on this subject. Ten trees in one of the worst diseased areas were 

 selected for this purpose and the leaves with Stilbella spots removed, 

 two rows of the surrounding trees being similarly treated to prevent 

 too immediate reinfection from other trees. The effect of the leaf 

 picking on the prevalence of the fungus was roughly determined by 

 finding the relative proportions of diseased and healthy berries, both 

 being counted, in the trees of the plat and in an equal number of 

 those outside. The proportion of diseased berries in the trees of the 

 plat in the crop immediately following the first picking of leaves 

 was 38 per cent; in the outside trees, 10 per cent. During the year 

 the leaves were picked at intervals of three months. At the end of 

 the year the percentage of diseased berries in the trees with picked 

 leaves had declined to 16 per cent, but in the outside trees had in- 

 creased to 32 per cent. It is probable that an equally large increase 

 of Stilbella-affected berries would have been found in the trees from, 

 which the diseased leaves were picked if it had not been for this 

 treatment, the disease having made great headway in all parts of 

 the plantation. 



Further work in combating the disease was made impossible by 

 a change in the management of the plantation where the work was 

 being carried on. However, such results as have been obtained 

 would indicate that the disease might be successfully combated by 

 removing the diseased leaves. No doubt the defoliation 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 com- 

 paratively slowly and that the diseased leaves are readily recog- 

 nized 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 



