20 



have died. Although it is as yet impossible to arrive at definite con- 

 clusions, it would seem that treatment of the soil with some sub- 

 stance rendering conditions unfavorable for the growth of the fungus 

 was of practical value. 



As to the cost of materials used, that of lime sufficient for 100 

 square meters is but 35 cents. The cost of sulphur at the rate used 

 in the experiment would be 10 times as much. However, it would 

 be worth while to use even such remedies if cheaper materials were 

 less successful. If begun while the diseased areas are not too large 

 the expense for such treatment would be small. 



As copper sulphate is a substance which is injurious to plant life, 

 except in very small quantity, it was not thought desirable to apply it 

 so freely to the soil as the other substances used. Accordingly it was 

 applied only to the trees near those attacked by Rosellinia. A quan- 

 tity equivalent to 15 grams of the salt was sprayed about the base of 

 the trees. Within a few weeks the fungus had passed the sprayed 

 trees, killing all the Petiveria except near the coffee trees. The form 

 of the disease that remains in places where the fungus has passed 

 seems to be less virulent, probably because less well nourished. After 

 the copper salt has been washed out b}'^ rains the trees so treated will 

 probably be subject to attack from the fungus as soon as enough food 

 material accumulates to give it sufficient start. The spraying of the 

 entire surface with a solution of copper sulphate was tried, the spray 

 being of such concentration as to equal 25 grams of the salt per square 

 meter. This was found in an experiment on 8 square meters of land 

 badly infested with the black-root disease to be sufficient to check and 

 apparently to exterminate the fungus, which has not reappeared 

 during the year which has passed since the spraying. The cost for 

 the copper salt alone used at this rate amounts to 50 cents, at local 

 prices, for a quantity sufficient to treat 100 square meters. Where 

 the drainage is good, as on the clay hillsides, not enough of the copper 

 is retained in the soil to be harmful to vegetation. Under such con- 

 ditions and on soil suitably cleaned this is an effective remedy. Pos- 

 sibly a considerably smaller quantity of the copper salt would be 

 equally effective. However, since satisfactory results can be secured 

 by other means, the use of copper salts in controlling the disease is 

 not to be recommended. 



The work carried on so far would indicate that cleaning the land, 

 ditching, and liming were of value in combating this disease. The 

 cleaning includes the taking up and removal of the diseased and dead 

 coffee trees. The usual custom of cutting off the tops of such trees 

 and leaving the stump to decay is bad. Such material, together with 

 piled-up leaves, branches, and other debris, half-decayed vegetable 

 matter which serves the fungus as food material, should be gathered 

 in the infested places and burned. Large stumps that can not be 



