192 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



writer to attempt in a brief compass to show the most important 

 points to be considered in the treatment of plants. 



But it should be distinctly recognised that local experience, 

 and experiment, are the only real guides to a successful result. 



Classes of Pests. 



Almost all the serious pests that attack plants are insects or 

 fungi. We can take them in order as they attack a plant. 



1. Boot-feeding Insects, which attack the roots of plants. They 

 may devour the roots, suck the sap, or cause swellings to form, 

 and the same insect may even attack the plants above ground as 

 well as at the roots. 



2. Boring Insects, which live within the plant, and mostly 

 attack the stem or trunk, but also bore the leaves and fruit. 



3. Sap-sucking Insects, which attack the upper part of the 

 plant, boring in the leaves and stems to obtain their food. They 

 resemble those that suck the sap from the roots, but the last are 

 a much more difficult economic problem. 



4. Defoliating Insects, which eat up the leaves and other green 

 parts of plants. 



5. External Fungi, growing over and living upon the exposed 

 parts of the leaves and stems of plants, and only sending feeding 

 suckers into the plants. 



G. Local Fungi, which enter the plant, but remain at the 

 point where they found an entrance, and only spread by the 

 spores being carried to other parts of the plant, and there 

 growing into it again. 



7. Benctrating Fungi, which have the power of passing from 

 one part of a plant to another by boring their way through the 

 plant. Each of the classes of pests must be treated in a different 

 way, and usually the remedy for one would be entirely useless if 

 applied for a pest of another class. 



Insects. 



Boot-feeding Insects. — Fortunately the number under this 

 class is not many, for there is no remedy known, that is practical 

 for general use, by which they can be treated. It is not becauso 

 the insects are hard to kill, but because the nature of the soil is 

 such that it is very difficult to reach them. The best of the 

 known processes — the use of carbon bisulphide — is not certainly 



