CONTROL OF Two ELM-TREE PESTS 



young larvae begin their mines at once. The majority of the eggs are 

 probably deposited, in most seasons, in the middle of May. 



The larvae grow rapidly, and by July i all have practically completed 

 their growth and gone into the ground under the tree. Here they burrow 

 downward an inch or less and soon make a thin, brown, papery cocoon 

 in which they hibernate until the next May. Apparently they pass the 

 winter as larvae, changing into pupae in the spring. Thus there is but 

 one brood a vear. 



C 



FIG. 1 80. Larvae, of elm leaf -miner, much 

 enlarged 



FIG. 181. Three eggs of elm leaf- 

 miner stuck in leaf. Much 

 enlarged 



NATURE OF INJURIES CAUSED BY THE ELM LEAF-MINER 



The work of this miner becomes very conspicuous in June. The leaves 

 become blotched and blistered by the mines of the larvae. Several miners 

 usually attack a single leaf and their mines eventually coalesce and form 

 large, whitish blisters (Fig. 178). Often the inner tissues of nearly the 

 whole leaf are mined out, forming a blister over the entire area of the 

 leaf. The leaves then wither and turn brown and the tree looks as though 

 it had been scorched by fire. Unless the leaves are wholly mined they 

 remain on the tree. Small trees are often almost defoliated, especially 

 small Camperdown elms. A half dozen small English elms standing in 

 a group on the campus have been most seriously injured for several 

 seasons. 



