INSECTS AFFECTING 1>AKK AND WOODLAND TREES 225 



its nourishment from underlying tissues, it can be controlknl only by the use 

 of some substance powerful enough to penetrate the covering scale and 

 destroy the underlying insect. A large number of materials have been 

 employed for this pur])ose. The nearly naked crawling )-oung are un[)ro- 

 tected and on that account easily killed. The great difficulty of attempting 

 to check the insect in this stage, is that \c)ung are produced during an 

 e.xtended period antl therefore the best results have bet-n obtained bj- the 

 use of materials powerful enough to penetrate the sheltering scale of the 

 adult, and such materials are so strong that they can be applied to decid- 

 uous trees only when in a dormant condition. The best results, as a rule, 

 have been obtained by early spring applications, preferabh' deferring the 

 treatment till shortly before the buds begin to open. 



A wide variety of materials have been employed, prominent among 

 which may be mentioned whale oil soap solution, kerosene emulsion, crude 

 petroleum and its emulsions and the lime-sulfur washes. The whale oil 

 soap solution at the rate of 2 pounds to i gallon of water, is fairly effective 

 though costly, and in commercial orchards, has quite generally given way 

 to other materials. Both kerosene and crude petroleum in pure and 

 mechanical emulsions, have been employed to a considerable extent, but 

 in most cases they likewise have been displaced by the cheaper, safer 

 lime-sulfur washes which, as a rule, have been most successful. There 

 are many formulas for these latter, some of which have been used for years 

 and others developed within 12 months. The formulas for several excellent 

 washes and methods of preparing the same, have been given on page 39, 

 to which the reader is referred for further details. It is well to bear in 

 mind when fighting this insect, that thoroughness is absolutely essential, and 

 that it lies within the power of the man at the nozzle to make or mar the 

 entire work. It is advisable, before spraying, to cut the trees back as much 

 as possible, and in sections where this scale is prevalent, low heading will 

 doubtless become popular because of the greater ease in fighting this pest. 

 Another important point is to spray with the wind wherever conditions 

 permit, making the application on the other side of the trees when the wind 



