56 



direct methods of destruction aimed against them, 

 and are rapidly spreading to new territory all the 

 time. The only hope of their ultimate control seems to 

 be the introduction of natural enemies from European 

 countries where the insects have long existed, and 

 where certain natural enemies largely hold them in 

 check. Many efforts are being made to introduce 

 and develop some of these enemies in this country 

 throughout infested districts. It is altogether prob- 

 able that some organism already present in this 

 country may yet adopt these pests as their host and 

 eventually help to control and check their damage. 

 Diseases of plants are more insidious in their at- 

 tacks than insects. Oftentimes the presence of the 

 trouble is not suspected until long after infection 

 has occurred and the plant begins to die from the 

 effects of the same. Here, even to a greater extent 

 than with insects, is it necessary for the intelligent 

 grower to have some knowledge of the character of 

 the more common diseases likely to attack his plants 

 and the manner in which they manifest their pres- 

 ence before intelligent treatment can be given. 



For purposes of treatment the common diseases 

 may be divided into the following very general 

 classes: First, local diseases consisting of those 

 which are generally confined to local sections of the 

 host and which do not spread rapidly through the 

 tissues of the plant. Diseases of this class may be 

 effectively controlled by cutting away the infected 

 parts. 



Second, the surface or superficial diseases, such 

 as the mildews and molds. Direct applications of 

 bordeaux mixture or various sulphur compounds 

 effectively destroy diseases of this class. Internal 

 diseases, such as the various rots, rusts and smuts. 



