62 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 47 



Control Measure 2 or 3 (end of circular) as soon as insects 

 are found. Spray should be directed to under sides of leaves. 



Two-Spotted Spider Mite, Tetranychus telarius (L.). — The 

 foliage of redbud trees is sometimes infested with great num- 

 bers of green or yellowish mites of this species. The mites remove 

 so much chlorophyll and juice from the foliage that the leaves be- 

 come dry and drop prematurely. The overwintering female mites 

 move to the leaves in early summer to feed and deposit trans- 

 lucent, spherical eggs. Six-legged larvae hatch from the eggs in 

 a few days. After the first molt, the mites have eight legs. Follow- 

 ing two more feeding periods and molts, the mites become adult. 

 The mites of various stages differ in size but are similar in ap- 

 pearance. Males are slightly smaller than females, and their ab- 

 domens are more pointed than those of females. There may be a 

 number of generations of this mite during the summer. 



Control Measure 9 (end of circular). 



Oystershell Scale, fig. 5. — See under Ash. Control Measure 

 5 (end of circular) in late winter or Control Measure 3 about the 

 first of June, after eggs hatch. Thorough spraying is essential. 



SPIREA 



Spirea Aphid, Aphis spiraecola Patch, fig. 44. — This green 

 plant louse occurs nearly every spring in great numbers on the 

 tender shoots of spirea. Eggs deposited on spirea in the fall give 

 rise to mother aphids that produce living young in the spring. 

 Wingless and winged forms may be present ; the latter migrate 

 to other host plants as the plant growth hardens. Quantities of 

 sticky honeydew are produced by an infestation of this aphid. 



Control Measure 3 (end of circular). 



SPRUCE 



Spruce Spider Mite, Oligonychus ununguis (Jac). — The 

 spruce spider mite is small, but its dense populations can do a 

 great deal of damage. It is one of the most troublesome pests of 

 arborvitae, spruce, and juniper. It lives on the juices of these 

 plants. When the sharp green color of the foliage begins to give 

 way to gray, and later brown, it is too late to prevent some de- 

 gree of damage, but prompt action may prevent serious damage 

 or death of the plants. 



