HANDBOOK OX INSECT ENEMIES OF FLOWERS AXD SHRUBS 79 



Treatment and prevention. — The 



best way to control these three borers 

 is to cut off and burn the infested shoots 

 as soon as the injury is discovered. 

 Spraying the rose foliage with lead 

 arsenate in June and July will kill 

 many adults of the rose stem girdler, 

 which feed on the leaves during the 

 egg-laying period. 



Leaf-Cutter Bees 



The leaf-cutter bees, belonging to the 

 genus Megachile, frequently attract 

 attention by the circular areas which 

 they cut from the leaves (fig. 132). 

 Rose foliage is most often used for this 

 purpose, although the leaves of locust 

 and other plants are also cut. These 

 pieces of leaves are used in forming a 

 thimblelike cup or cell for the young. 

 These cells or nests are made in the 

 pruned or broken ends of branches or 

 in the pithy stems of plants such as 

 dahlia (fig. 133). As the larvae hollow 

 out the pith of living plants the injured 

 portion is killed. These leaf-cutter 

 bees are of medium size, usually black, 

 brown, or metallic green or bluish. 

 Certain other species of bees and wasps 

 occasionally also have a similar habit of 

 nesting in the pith of various plants. 



Treatment. — Wilted or dying shoots 

 containing the nests should be de- 

 stroyed. The cutting of the leaves is 

 usually not extensive enough to cause 

 serious injury to the plant. 



Figure 132. — Circular areas cut from 

 rose foliage by a leaf-cutter bee 



Figure 133. — Larva of leaf-cutter bee 

 in rolled leaves inside a dahlia stalk. 

 Slightly enlarged. 



Rose Sawflies, or Slugs 



The larvae of three species of sawflies 

 injure roses by skeletonizing the foliage 

 or chewing large ragged holes in the 

 leaves. The larvae are often referred 

 to as false caterpillars, or slugs. The 

 adults are small wasplike insects, and 

 the females deposit their eggs in slits 

 "sawed" in the leaves. 



The bristly rose slug (Cladius isomerus 

 Xort.), when young, skeletonizes the 

 leaves on the underside, imparting a 

 glazed appearance to the foliage. As 

 the slug increases in size it eats large 

 holes (fig. 134) or the entire leaf tissue, 

 leaving only the larger veins. When 

 full-grown the larva is about half an 

 inch long and is dirty yellowish green 

 with a darker green stripe on its back. 

 The body bears stiff hairs, from which 

 it derives its name. This species has 

 about six generations a year in the 

 neighborhood of Washington, D. ('.. 

 and overwinters in cocoons in protected 

 places, such as rubbish. The cocoon 

 is a thin, transparent, papery covering 

 which sometimes has a pale-brownish 

 tint. 



