56 MISC. PUBLICATION 626, U. S. DEPT.OF AGRICULTURE 



suck the sap for food. Infested branches 

 may be weakened or killed. This aphid 

 is about V% inch long, reddish brown, and 

 its body is partly covered with a white 

 powdery secretion. The aphids are not 

 easily noticed because their color re- 

 sembles that of the bark; however, the 

 presence of ants, wasps, and flies about 

 the trees, attracted by the honeydew 

 excreted by the aphids, may call atten- 

 tion to them. Infestations occur in the 

 spring, and the aphids apparently leave 

 the trees before midseason. Frequently 

 the injury is not noticed until after the 

 insects have left, and the only evidence 

 that remains is the sooty appearance of 

 the foliage caused by a black mold that 

 develops in the honeydew. 



Treatment. — See treatment for 

 aphids (p. 9). 



Other Pests of Juniper 



Bagworm 



Spruce spider mite. 



Page 

 .. 19 

 - 85 



LILAC 



Lilac Borer 



The lilac borer (Podosesia syringae 

 syringae (Harr.)) is the caterpillar of one 

 of the clear-winged moths. The borers 

 tunnel under the bark and into the wood 

 (fig. 90), weakening the stems or girdling 



Figure 90. — Work of the lilac borer 



them and causing the foliage to wilt. 

 Roughened scars showing the old borer 

 holes may occur on the larger stems at 

 places where the borers have worked for 

 several seasons in succession. The cater- 

 pillar is creamy white and about % inch 

 long when full-grown. It passes the 

 winter in the tunnels in the stems. The 

 adult moths emerge in the spring and 

 early summer and usually lay their eggs 

 on roughened or wounded places on the 

 bark. In addition to lilac, this borer 

 attacks ash and mountain-ash, and 

 occasionally privet. 



Treatment. — Cut and burn before 

 spring the dying and unthrifty stems 

 containing the borers. During the 

 summer watch for evidence of fine boring 

 dust being pushed from small holes in 

 the bark by the young borers and cut 

 these out with a' sharp knife. Where 

 the borers have entered the wood they 

 can be killed by injecting a few drops 

 of carbon disulfide (p. 103) into the 

 tunnels. The openings should be closed 

 immediately with some gasproof ma- 

 terial, such as grafting wax, putty, or 

 wet clay, and kept closed for a day or 

 two to retain the fumes. The larger 

 wounds may then be cleaned and 

 painted over with shellac or a tree- 

 wound dressing. Sometimes where the 

 tunnels are fairly straight the borer can 

 be killed by probing with a flexible wire, 

 or pulled out by means of a hooked wire 

 to make certain of its destruction. 



Oystershell Scale 



The oystershell scale (Lepidosaphes 

 ulmi (L.) (fig. 91) is shaped like a minia- 

 ture oystershell, about % inch long and 

 brown to brownish gray. When numer- 

 ous these small sucking insects often 

 coat the bark of twigs, branches, and 

 smaller stems. The plants become 

 weakened, produce undersized foliage, 

 or may be killed if a heavy infestation 

 continues. This scale insect is widely 

 distributed and attacks many kinds 

 of trees and shrubs, having been re- 

 corded on more than 100 different host 

 plants. Among these are ash, boxwood, 

 dogwood, lilac, maple, poplar, tree 

 peony, and willow. Lilac is commonly 

 attacked. One form of this scale also 

 attacks fruit trees. The winter is passed 

 in the egg stage under the female scales. 

 Hatching of the young crawling stage 

 starts in the spring about the time the 

 apple blossoms are falling. A second 

 generation of young is produced late in 

 July and in August in the southern half 

 of the countrv. 



