INSECTS, DISEASES, AND INJURIES 



ISI 



is objectionable, the insect may be eliminated almost entirely 

 by collecting and destroying the cocoons in the autumn. The 

 soil and litter around the tree should be removed to a depth 

 of an inch or two and carted away. It should be buried or 

 disposed of in such a way as to kill all the cocoons. Isolated 

 trees may be rendered free from attack for several years by 

 this treatment. 



Woolly larch aphid (Chermes 

 strobilobius, Kaltenbach). 

 Fig. 17. 



The leaves of the larch are 

 often badly infested by a 

 small, nearly black plant-louse 

 which covers itself with a con- 

 spicuous mass of wax-wool. 

 Infested trees often have the 

 appearance of being dusted 

 with flour. 



The life history of this 

 plant-louse is extremely com- 

 plicated. The insect hiber- 

 nates both on larch and on 

 spruce and can breed for at least two years on larch, but 

 there is a regular migration between these two trees. On the 

 spruce the lice form galls which are similar to those of the 

 spruce gall aphid. On the larch the over- wintered females and 

 their eggs may be found in abundance in early May at the 

 base of the leaf-clusters. On hatching, the young crawl to 

 the leaves where they settle down and secrete a white waxy 

 covering. The aphids are most abundant in late June although 

 they are present in smaller numbers until fall. 



17. Chermes strobilobius. 



