June 15, 1914 
Citrus-Root Nematode 
2 29 
needed is the careful application of well-known suitable cultural methods. 
Where the climate, soil, and cultural conditions are suitable to the 
Citrus family these diseases will not appear, or will appear in such a mild 
form as to be largely negligible. An examination of the literature of 
Citrus diseases and of the fungi and other microorganisms which have 
been found parasitic upon Citrus trees discloses a long list of parasites, 
so long, indeed, as to suggest that species of Citrus are liable to the 
attacks of an unusually large number of parasitic microorganisms. The 
foregoing remarks, of course, apply only to aerial parts of the tree. If, 
therefore, among these numerous parasites of the above-ground portion 
of the tree, relatively few are found that are really harmful, the thought 
arises that something similar may be true of the subterranean parasites. 
Should this prove true and should Tylenchulus semipenetrans prove to be 
one of a series of rather harmless parasites which attack the roots of 
these trees, the injurious results of which may be combated by proper 
cultural methods, then all may be well. This, however, is something that 
needs to be demonstrated. The history of this parasite is altogether too 
recent and incomplete to render final judgment possible. Hence the 
necessity for several years' further careful observation. 
It will have been noticed that the evidence thus far accumulated is, in a 
considerable number of cases, indecisive. It may be compared to a two- 
edged sword, which may cut in either direction. The parasite is found 
to be somewhat more abundant in orchards that are out of condition, but 
so far as the present evidence goes, this may be either because the parasite 
is there and causing the difficulty, or because the trees are out of condition 
for some other reason, and therefore are not resistant to the parasite. On 
the other hand, the parasite is found on the roots of trees which appear 
to be in good health. Here, again, this may be either because the parasite 
has not yet been there sufficiently long to cause visible injury or because 
healthy trees do not have much difficulty in counteracting the bad effects 
undoubtedly due to the parasite. It would, however, be unwise for 
Citrus growers to allow such reasoning to lull them into a feeling of 
security. History abounds with similar cases in which either apathy or 
optimism has led to deplorable inaction, permitting devastating diseases 
to continue on their course unchecked. 
Tylenchulus semipenetrans is distributed from place to place on nursery 
stock. This is the method by which in all probability it is most frequently 
distributed from one district to another, and it follows that any method 
of inspection by which infested nursery stock can be readily distinguished 
from noninfested will make it possible to establish at least one efficient 
check on the spread of the disease. 
As Tylenchulus semipenetrans is a parasite with which from now on 
Citrus growers will have to reckon, it seems certain that sooner or later 
appropriate inspection will be undertaken by Federal authorities, by 
State authorities, and by private enterprise. The most beneficent inspec- 
