ENGLISH: ILLINOIS TREES: TKEIR INSECT ENEMIES 59 



POPLAR 



The fast-growing poplars, Lombardy, Carolina, aspen, and 

 cottonwood, are almost certain to be short-lived because of the 

 ravages of borers. Some of these borers are discussed briefly be- 

 low. 



Poplar Borer, Saperda calcarata Say. — The white, cylindrical 

 larva, which does the boring, and the adults, bluish-gray beetles, 

 are each more than an inch long. Eggs deposited in slits in bark 

 in the summer produce the borers that work under the bark and 

 sapwood and into the heartwood of an infested tree. Frass or 

 sawdust at the base of a tree indicates the presence of borers. 

 Three years are required for the life cycle of this insect. 



Control Measure U (end of circular) . Heavily infested trees 

 should be cut down and burned in the early spring. 



Cottonwood Borer, Plectrodera scalator (F.). — The adult 

 form of this insect is a large beetle with long, black antennae. 

 The female lays eggs in cavities dug in the bark. The eggs pro- 

 duce white, deeply constricted grubs that when grown are up to 

 2 inches in length. These grubs, the tunnels of which are plugged 

 with wood fibers, work near the bases of trees or even below 

 ground. Badly infested trees may be easily blown over. Two 

 years are required for the life cycle of this insect. 



Control Measure U (end of circular) ; or wire screen may be 

 placed around the bases of trees to prevent egg laying. 



Poplar and Willow Borer, Sternochetus lapathi (L.). — The 

 larva of this insect is a legless grub or borer, about one-half inch 

 long, that bores into poplars and willows. The adults are black 

 snout beetles or weevils. The borer feeds in the limbs and 

 branches, as well as in the trunk, of the tree it infests. It prefers 

 wood 2 or more years old. 



Control Measure 4 (end of circular) . Infested branches and 

 limbs should be removed and burned before July. 



Carpenterworm, Prionoxystus robiniae (Peck). — The larva 

 of this insect is a pinkish, slightly flattened caterpillar, up to 

 2y 2 inches long, that develops from an egg deposited in a bark 

 crevice by a large, gray moth. The carpenterworm requires 3 

 years to complete development, during which time the larva 

 mines and loosens the bark and drills large holes into the trunk 

 of the infested tree. It may deform trees and branches. 



Control Measure U (end of circular). 



