IXSECTS AFFECTING PARK AXD WOODLAND TREES 225 



its nourishment from underlyinn;- tissues, it can Ije controlled only by the use 

 of some substance powerful enou>^h to penetrate the covering; scale and 

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

 employed for this purpose. The nearly naked crawling young are unpro- 

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

 to check the insect in this stage, is that )oung are produced during an 

 extended period and therefore the best results have been obtained bv the 

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

 adidt, and such materials are so strong that the\- can be applied to decid- 

 uous trei;s only when in a dormant condition. The best results, as a rule, 

 have been obtaineil by earl\- spring applications, preferably deferring the 

 treatment till shorth' l)efore the butls begin to open. 



.\ wide \ariety of materials have been employed, prominent among 

 which ma\ be mentioned whale oil soap solution, kerosene emulsion, crude 

 l)etroleum and its emulsions and the lime-sulfur washes. 'Ihe whale oil 

 soap solution at the rate of 2 j)ounds 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 the)' likewise have been displacetl 1)\' the cheaper, safer 

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

 are many formulas for these latter, some of which ha\'e Ijeen used for \'ears 

 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 



