160 Principles of Plant Culture. 



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. 

 These classes will be considered in their order. 



A PLANTS AS AFFECTED BY ANIMAL PARASITES. 



a By quadrupeds and birds. The four-footed 

 animals that injure cultivated crops nearly all belong to 

 the class known as rodents, which includes mice, go- 

 phers, rabbits, woodchucks, moles, etc. These may 

 usually be controlled by trapping, shooting, or poison- 

 ing, or by protecting the plants. 



271. Damage from Mice to orchard and nursery 

 trees is very common. Mice are usually more trouble- 

 some on sod ground covered with snow, especially be- 

 neath snow banks, hence all grass should be removed in 

 autumn from the immediate vicinty of the trees. It 

 is well to ridge the soil a little, directly about the trees, 

 so that the mice in burrowing beneath the snow will 

 not be likely to come in contact with the stems. Pack- 

 ing the snow immediately about the trees is helpful 

 when damage is discovered during winter. The stems 

 of orchard trees may also be wrapped in heavy paper 

 or inclosed in fine wire netting. If tarred paper is used, 

 it should be promptly removed in spring, or it may in- 

 jure the bark. 



