92 INSECTS AFFECTING THE ORANGE. 



the circulation through the roots of the plant, would be far more likely 

 to injure the plant itself than the Bark-lice upon it. 



Inoculating with Poisons. For the same reason it has been found im- 

 possible to reach and destroy insect pests by inoculating the bark or 

 wood of the trunk or branches. 



The attempt has usually been made by boring into the trunk of the 

 tree, introducing the article to be tested, and tightly closing the hole 

 with a plug. Numerous experiments of this sort are recorded. Of the 

 long list of substances which have been thus tried, and which includes 

 many mineral and vegetable poisons, as well as sulphur and other sub- 

 stances possessing insecticide properties, none have proved effective. 



Popular Fallacies. There is a widespread and apparently well-founded 

 opinion that vigorous trees are in little danger from attacks of Scale- 

 insects, but if from any cause a tree becomes enfeebled, its investment 

 is only a question of time. Many persons therefore reject the aid of 

 insecticides, and when a tree becomes infested, rely upon a liberal use 

 of fertilizers to restore its lost vitality and force it into vigorous growth, 

 believing that in this way it will rid itself of the pest. It cannot be de- 

 nied that this course of treatment is often successful, at least for a time, 

 but the Scale-insect is never entirely eradicated, and its return at some 

 future time may be expected. Indeed, overstimulation by means of 

 fertilizers is apt to defeat its object, and reaction follows in unfavorable 

 seasons. 



In fighting Scale with fertilizers, therefore, success may be said to 

 depend upon conditions unknown or beyond our control. When these 

 are favorable, the system may be found to work well; otherwise failure 

 is inevitable, and by adhering to it valuable time will be lost, and the 

 pest will perhaps be allowed to spread until it can with difficulty be 

 controlled. 



' EFFECTIVE REMEDIES. 



Kerosene. This is without doubt the most effective insecticide for use 

 against Scale-insects, and it is almost the only substance known which 

 will with certainty kill their eggs without at the same time destroying 

 the plant. The difficulty of diluting it, and the danger to the plant of 

 applying it undiluted, have long prevented its extensive use. Easy 

 methods of emulsifying the oil and rendering it miscible with water are 

 now known, and have recently been set forth by Professor Eiley in his 

 official reports. 



Milk and Kerosene Emulsions. The method of- emulsify ing kerosene 

 with milk, as given in a preliminary report on Scale-insects in the Ee- 

 port of the Commissioner for the years 1881 and 1882, remains the 

 best and simplest, where milk can be easily and cheaply obtained. 

 The milk should first ba heated nearly to the boiling point, and then 

 mixed with kerosene in the proportions one part of milk to two parts 



