specific Pests 149 



Othen\dse, applications of hot water, which does not injure 

 the roots, is recommended, or else the use of tobacco dust, 

 the nicotine of which leaches into the soil with the rains and 

 kills at least the plant-lice, while acting at the same time as 

 a fertilizer. This ground tobacco is best placed in a trench 

 around the tree, filling it liberally and re-covering the 

 trench. 



The application of potash fertilizers, such as kainit, or 

 muriate of potash, preferably before or during a rain, sown 

 broadcast or worked into the soil (ten pounds of kainit to a 

 fixe or six year old tree) is said to destroy the grubs and any 

 insect that lives in the soil. At least the tree will be bene- 

 fited by the application and so in\'igorated as to resist the 

 attacks, not only of this, but of any other insect pest. 



Specific Pests. Since the methods of combating the vari- 

 ous insects are based on their life habits, and since these 

 differ considerably, it is necessary to specify more fully 

 with reference to particular pests. In the following pages, 

 therefore, the more obnoxious insects are more systemat- 

 ically treated and the more common enemies to shade trees 

 are briefly described as far as needful; and the methods of 

 controlling them are briefly given. It would not be prac- 

 ticable within the limits of this book to give more than the 

 briefest statements. Those interested in further detail 

 must find it in the very comprehensive literature, a partial 

 reference list to which is found on page 375, and especially 

 to the excellent work of J. B. Smith, "Economic Entomol- 

 ogy for the Farmer and Fruit-grower." 



The insects obnoxious to tree growth may be roughly 

 classed in the three large groups of bugs, beetles, and 

 butterflies (including moths), each of which can be again 

 subdivided into several smaller groups according to the 

 character of the insect or its feeding habit. 



