IS 



plant is killed outright, for its food and water supply is entirely cut 

 off. These effects, therefore, are not brought about directly by the 

 nematodes, but only indirectly. That is to say they are not due to 

 the direct action of the worm in feeding upon the root as is the case 

 with the attacks of insects and fungous diseases, where the plant 

 dies or sustains injury from the loss of its vital substance. To be 

 sure the worms obtain their food from the roots after entering them, 

 and must cause some damage in that way, but far more serious must 

 be the result of the derangement of -the vital functions caused by 

 the abnormal growth of the plant, which in trying to overcome the 

 injury in the roots produces greater injury to its other parts. It is 

 evident from published writings, even in experiment station bulletins, 

 that a very general impression exists that nematode worm injuries are 

 brought about by a swarm of little worms feeding upon the roots, 

 much as insect larvae feed, but this idea is altogether wrong. The 

 amount of food which the worms consume is insignificant and 

 entirely disproportionate to the amount of damage caused. The 

 structure of the affected roots, on the other hand, shows plainly that 

 therein lies the chief source of injury. 



Secondary Effects. 



In this connection it will be proper to consider what we may call 

 the secondary effects of these nematode attacks. This would 

 inckide the attacks of other injurious organisms which are favored 

 by the weakened condition of nematode affected plants. Among the 

 most common of these organisms are those fungi which produce 

 diseases. It is a well known fact that the least vigorous plant is 

 most easily affected by disease. While it is true that some of the 

 most destructive plant diseases attack the strong and weak alike, in 

 the case of many others like certain "mildews", "blights", "spots", 

 etc., the disease only appears on plants which for some reason are 

 not growing vigorously. We believe that the destructive effects of 

 the well known " violet disease " (Cercospora Violae) are greatly 

 increased as secondary results of nematode galls on the roots. That 

 is the galls have weakened the plants and thus given the fungus a 

 foothold. In the same way we have seen the cucumber powdery 

 mildew appear on nematode ridden plants while others in the same 

 house which had no nematodes were likewise free from mildew. 

 The tomato blight might easily be induced in the same way. We do 



