EXTERMINATING NOXIOUS INSECTS. 275 



left, and then only by the dead roots which they leave be- 

 hind. Small roots, when punctured by them, become knot- 

 ty and greatly deformed ; but large roots, at the collar of 

 the tree, may be sucked dry by them without showing 

 knots. On this account, the real cause of the death of the 

 tree is often overlooked. Indeed we have known persons 

 possessing much entomological information inspect trees 

 killed or damaged without for once suspecting that root 

 lice had any agency in producing the results. Probably 

 there are but few persons who are aware to what extent the 

 Woolly Root Louse injures apple-trees, or how readily they 

 discriminate between roots of trees which are healthy and 

 those that are wounded. 



The Woolly Aphis. This scourge of young apple-orchards 

 (Fig. 106) is sometimes alluded to as the "American Blight." 

 But entomologists assure us that it is a species Fig. 106. 

 of Aphis, or Plant Louse. We frequently see it (j 

 on the branches of young trees covered with tine m 

 white downy hairs. In some instances, they are Wo( ^ y Ap _ 

 so numerous as to destroy a streak of the bark on P le Lonse - 

 a limb the entire length. They are voracious feeders. They 

 suck out the juice of the tender branches with surprising ra- 

 pidity. We have seen branches of trees with a dark-colored 

 streak for several feet in length, where these depredators 

 had been destroyed, which appeared as if a red-hot iron 

 had been drawn along the bark. 



The only true mode of extermination is to apply whale- 

 oil soap with a swab, or strong lime-wash, rubbing the af- 

 fected parts until every vestige of the depredators is wiped 

 out. Then let the streak of injured bark be covered with 

 liquid grafting-wax, or pitch and tallow. 



Aphis, or Aphides. We frequently see untold numbers 

 of the aphis (represented by Fig. 107, on the following 

 page), which is about the usual size of these depredators, 



