60 JOURNAL OF AGRICULTUnE OF P. R. 



revealed that a high-water table was the primary cause, it being 

 in some places within two feet of the surface. Neighboring trees 

 on slightly higher land were unaffected. The trees had grown nor- 

 mally for a number of years, until their roots began reaching down 

 below the water level. From this time on they became unthrifty, 

 as evidenced by a yellowing of leaves, and dying back of twigs and 

 branches. After a longer or shorter such period, death came sud- 

 denly. The final wilting of the leaves and drying out of the bark 

 often took place within a very few days', as a result of girdling at 

 the crown by a fungus, which had worked up along • one or more 

 of the main roots. This fungus {Vstiliua vulyaris) is very common 

 on dead wood, and is not generally considered parasitic. In the 

 present case it had undoubtedly acted as a wound parasite, gaining 

 entrance through the ends of the roots killed by the water. The 

 fruiting or reproductive bodies were produced around the crown 

 shortly after the death of the tree, as black, carbonous, crust-like 

 layers, pitted wdth the innumerable openings into the spore sacks. 

 Affected roots and trunks showed a characteristic dry white rot. 



No indications have been found at any time of the presence of 

 the truly parasitic root fungi reported from other citrus regions, 

 RoseUinia spp., SpkaerosHIhe, Fomes, or Arm ill aria mellea. These 

 fungi are serious for the most part only where there is an abundance 

 of dead wood in the form of logs or stumps scattered through the 

 groves, on which they gain a foothold, and from which tliey spread 

 to adjoining citrus trees. The fact that most Porto Rican citrus 

 groves have been set in what was formerly open pasture lands of 

 long standing, will make extremely improbable any infection from 

 fungi of this nature. One fungus {Valsa sp.) has been commonly 

 noted on exposed roots, and crowns of dead and dying trees. It 

 is also common on dead wood, and beyond imicli doubt has only 

 been able to attack, as did the Ustilwa, by working in through 

 wounds, or roots killed by standing water. It produces a di> rot. 



Fn all cases of death of trees in this manner, the first steps shovdd 

 be to look for poor drainage, which is [)rimarily responsibU' as far 

 as observations to date show. When this cannot be corrected in 

 low-lying sections of blocks of trees, replanting is not advisable, since 

 the same conditions will almost certainly recur. All dead and dying 

 trees should be removed, and care taken to dig out at least all of 

 the larger roots, which would otherwise serve to harbor injurious 

 fungi. Except where drainage is impossible or other factors inter- 



