CHAPTER XII 



PLANTS AS AFFECTED BY ANIMAL PARASITES 



THE only instance of a beneficial plant parasite (24) 

 of special interest to the cultivator is the micro-organ- 

 isms in the roots of leguminous plants, which we have 

 already considered (259). Many parasites of harmful 

 insects are beneficial, but these are beyond our scope. 

 We need, therefore, to treat here only those parasites 

 that are directly injurious to economic plants. 



270. Classes of parasites. The injurious parasites 

 of plants are very numerous and a scientific classification 

 of them is beyond the limits of this work. We shall only 

 endeavor to arrange the different parasites into groups 

 based on their manner of working injury and the methods 

 by which they may be controlled. 



With reference to the character of their injury and 

 the preventives used, as well as in their natural char- 

 acteristics, plant parasites are readily separable into two 

 great classes, viz., animal and vegetable parasites. 



The four-footed animals that injure cultivated crops 

 nearly all belong to the class known as rodents, which 

 include mice, gophers, rabbits, woodchucks, moles and 

 so on. These may usually be controlled by trapping, 

 shooting or poisoning, or by protecting the plants. 



Since worms, slugs and snails work the same kind of 



152 



