ENGLISH: ILLINOIS TREES: THEIR INSECT ENEMIES 33 



mines. Emergence of beetles begins about the middle of May in 

 Illinois and reaches a peak about the middle of June. A second 

 brood of beetles which follows reaches a peak emergence in 

 August. 



Control Measure 18 (end of circular). 



Banded Elm Leafhopper, Scaphoideus luteolus Van D. — 

 Rarely seen, this brown leafhopper, narrow and about one-fourth 

 inch long, is reported to be the carrier of phloem necrosis, a seri- 

 ous virus disease of American elms. The eggs of this insect over- 

 winter on the bark of elms and hatch in early spring ; the young 

 hoppers, called nymphs, feed on new foliage, producing a brown 

 area where the sap is withdrawn. The leafhoppers themselves 

 cause little direct damage, but the virus they carry from diseased 

 to healthy American elms is deadly to the trees. 



Control Measure 18 (end of circular). Spraying trees with 

 DDT will reduce the number of leafhoppers and check the spread 

 of phloem necrosis, but mite infestations may follow. 



Mites. — Several species of mites infest elms, but usually the 

 damage they do is of little consequence. However, following the 

 repeated use of DDT on elm foliage, infestations of the two-spot- 

 ted spider mite, Tetranychus telarius (L.), may become dense 

 enough to bronze the leaves by their feeding, and reduce the vi- 

 tality of trees. 



Control Measure 9 (end of circular). 



EUONYMUS 



Euonymus Scale, Unaspis euonymi (Comst.), fig. 26. — This 

 most important and destructive pest of euonymus is common 

 also on bittersweet and pachysandra. The great number of white 

 coverings of the males on the under sides of the leaves of in- 

 fested plants immediately attracts attention and serves to help 

 identify the pest. The female lives under a gray or brown shell, 

 shaped somewhat like the shell of an oyster. In spring, the over- 

 wintering female lays orange-yellow eggs, which produce 

 crawlers that leave the mother shell and find a place to settle and 

 grow on the host plant. This scale produces at least two genera- 

 tions a year. 



Control Measure 3 (end of circular) about July 1 when 

 hatching of eggs is complete. The spray should be repeated early 

 in September. 



