ENGLISH: ILLINOIS TREES: THEIR INSECT ENEMIES 3 



to borers. Newly planted trees suffering from transplanting 

 shock, and older trees growing in unfavorable places where little 

 moisture or food is available, become attractive to the pests. 



Leaf Eaters. — Severe damage by this group of pests is con- 

 spicuous and easy to detect. In many cases, however, damage 

 is not observed until serious defoliation has occurred. The prin- 

 cipal leaf eaters are beetles and their larvae (grubs) and the 

 larvae (caterpillars) of moths and sawflies. Damage by these 

 pests is most likely to occur in the spring and early summer. 



Mites. — Especially destructive to evergreens, these animals, 

 barely visible to the naked eye, have great reproductive power 

 and attack plants in large numbers. Some mites injure plants 

 by rasping the leaf surfaces and removing the plant juices. 

 Mites are not insects, although closely related to them. 



Gall-Producing Insects and Mites. — Galls are abnormal 

 growths appearing as warts or bumps or attractive-looking balls 

 on leaves and twigs. They are of many shapes and sizes, but 

 each kind is characteristic of the animal that produces it. The 

 production of some galls is stimulated by tiny mites too small 

 to be seen with the naked eye. The production of others is stim- 

 ulated by flies, aphids, and small wasps. A part of the life cycle 

 of the gall-producing animal is spent inside the gall. Most galls 

 do not cause serious damage to the plants on which they are 

 found. 



ABOUT TREES AND SHRUBS AND THEIR PESTS 



In the discussion that follows, the host plants are arranged 

 alphabetically. Each pest and the nature of its damage are 

 briefly described ; notes on the life history are given for each of 

 the common and destructive pests. The control measures are 

 numbered and are found at the end of the circular, pages 90, 91, 

 and 92, along with convenient dilution tables, page 89. 



AILANTHUS (TREE OF HEAVEN) 



Ailanthus Webworm, Atteva aurea (Fitch), fig. 1. — An oc- 

 casional pest of ailanthus, or tree of heaven, the olive-brown cat- 

 erpillar of this species feeds on the leaves under a thin web. 

 Sometimes it attacks the petioles, causing the leaves to wilt. 



Control Measure 1 or 2 (end of circular). 



