28 



the wood will be found to be blackened as if somewhat charred. A 

 fungus, Fusarium sp., is always present in the diseased tissue, but 

 inoculations with pure cultures have failed to produce the disease. 

 It is communicated readily to healthy trunks by means of small 

 pieces of diseased material, and when thus transferred has shown 

 itself to be rapidly developing and destructive, soon killing the 

 living tissue for several inches above and below the point of inocu- 

 lation. 



Infection appears to take place through wounds, as, for example, 

 the stumps left by cutting off part of the branches close to the ground. 

 It frequently accompanies the " white " root disease, attacking the 

 yet living trunk above the diseased roots. It seems probable that it 

 can attack the tree near the crown through small wounds such as 

 those made by the machete in weeding, but no clear evidence of this 

 has been found. The characteristic Fusarium was isolated from a 

 decorticating disease of coffee where all the trees were attacked -at 

 some 2 or 3 feet from the ground. In this case ants and mealy bugs 

 were also present, so that the injury was probably due in the first 

 place to these insects. The decorticated branches with the enlarged 

 outgrowths of healthy tissue at the base of the branches occasionally 

 to be seen are no doubt the after effects of this form of the trunk 

 disease. 



The foregoing includes all the commoner and more destructive 

 Porto Rican coffee diseases produced by fungi. One disease, that 

 caused by Hemileia vastatHx^ which is said to have caused so much 

 damage to the cultivation of this plant in India and the East Indies, 

 does not occur here and has not been reported from any American 

 coffee-growing country. The threadworm Heterodera radicicola^ is 

 often active in trees suffering from root disease, being found in such 

 cases at the upper edge of the diseased area at the base of the trunk 

 (PL VI). It was thought at first that it might be the real cause of 

 the white-root disease, but since specimens have been found free from 

 this worm there can be no necessary relation between the two. It 

 attacks the bases of the trunk, however, causing them to take on a 

 roughened, somewhat swollen appearance for a foot or so above the 

 soil. When cut into with a knife there may be seen, even with the 

 naked eye, the minute globular bodies of the adult females, by which 

 such diseased tissue is characterized. No real evidence that the trees 

 are really injured by this disease has been noticed. The character- 

 istic swellings caused on roots by this worm may sometimes be seen 

 on the fine roots near the surface. The heavy nature of most Porto 

 Rican coffee soils no doubt prevents it from becoming the pest which 

 it sometimes is elsewhere. 



