Specific Pests 149 
Otherwise, 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 
five 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 invigorated 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. 
