ILLINOIS NATURAL HISTORY SURVEY 



CIRCULAR 53 



includes weakened, dying, and recently killed elms, all elm wood- 

 piles (Fig. 13), bark on stumps (Fig. 14), and weakened or dying 

 branches on healthy trees. Proper disposal of elm material consists 

 of burning it before the beetles can emerge. 



Fig. 13. — Elm branches and trunks with bark intact and stored in ])iles are 

 excellent for colonization by bark beetles. For effective sanitation, such material 

 must be destroyed before the beetles can emerge. 



Fig. 14. I'^lm stubs and stumf)s left standing arc suitable for bark beetle 

 colonization. For effective sanitation, they must be burned, or the bark must be 

 removed, before the beetles emerge. 



