22 MISC. PUBLICATION 6 2 6, U. S. DEPT. OF AGRICULTURE 



Treatment and prevention. — Pro- 

 tect plants by applying a spray made 

 up of 5 ounces of powdered lead arsenate 

 and 3}i ounces of flour in 5 gallons of 

 water. For more complete information 

 on the life history and control of this 

 insect, write to the United States De- 

 partment of Agriculture, Washington, 

 D. C. 



Other Pests of Aster 



Page 



Spotted cucumber beetle 7 



Tarnished plant bug-- 25 



Four-lined plant bug 94 



Red spiders 11 



Cutworms 2 



Thrips 74 



Greenhouse leaf tier 5 



Stalk borer 34 



Potato flea beetle 67 



Wireworms 15 



White grubs 14 



AZALEA 

 Azalea Lacebug 



Typical injury by the azalea lacebug 

 (Stephanitis yyrioides Scott), shows as 

 a spotted or mottled grayish discolora- 

 tion and unhealthy appearance on the 

 upper surface of azalea leaves, with num- 

 erous flattened specks of blackish shiny 

 excrement on the lower surface. The 

 injury is like that caused by the rhodo- 

 dendron lacebug, as shown in figure 119, 

 page 73. The nymphs are small and 

 spiny. The adults are about %-inch 

 long, with lacelike wings lying flat over 

 the oval body, similar to those of the 

 lacebug shown in figure 45, page 28. 

 Nymphs and adults may be found during 

 the summer sucking the juices from the 

 under sides of the foliage. The winter 

 is passed in the egg stage on the leaves, 

 and hatching begins about midspring. 



Treatment. — Spray the under sides 

 of leaves when the insects are present, 

 especially when the nymphs first appear 

 in the spring, with either nicotine sulfate 

 or pyrethrum. A combination of white- 

 oil emulsion and derris powder (p. 10) 

 or of white-oil emulsion and nicotine 

 sulfate (p. 10) is effective and may be 

 used for heavy infestations. 



Mulberry Whitefly 



Azalea foliage becomes discolored as 

 a result of the sucking of the plant juices 

 by the mulberry whitefly (Tetraleurodes 

 mori (Quaint.)), especially when the 

 insect occurs in abundance. This white- 

 fly is found mostly on the lower leaf 

 surface. The nymphs appear as oval, 

 black, scalelike insects with a fringe of 

 white waxy filaments around the edges, 

 and are about the size of a pinhead. 



The adults resemble tiny white moths 

 and are similar in appearance to those 

 of the greenhouse whitefly (fig. 31, 

 p. 18). The insect is usually present 

 from spring until fall and may become 

 most numerous late in the summer. 

 Additional plants attacked are dog- 

 wood, holly, maple, mountain-laurel, 

 and mulberry, and occasionally others. 

 Treatment and prevention. — Same 

 as for the greenhouse whitefly (p. 18). 



Azalea Bark Scale 



Small, white, cottony or woolly 

 masses on the stems, especially in the 

 axils of the branches, usually indicate 

 the presence of the azalea bark scale 

 (Eriococciis azaleae Comst.). When 

 numerous these insects withdraw so 

 much sap for food that the plant is 

 weakened and appears sickly. Each 

 insect is enclosed in a white, feltlike sac 

 (fig. 35), and these sacs are the white 

 masses found adhering to the bark. 



Figure 35. — White, feltlike sacs cover- 

 ing females of the azalea scale on a 

 stem. About 3 times natural size. 



Treatment. — During the dormant 

 season, spray with a white-oil emulsion 

 diluted for dormant spraying. With 

 early-blooming varieties this can be 

 applied on a warm day in late fall, to 

 avoid spray injury to the blossoms in 

 early spring. After the blooming period 

 in the spring many of the newly 

 hatched, unprotected scale insects can 

 be killed by making two or more appli- 

 cations, 2 or 3 weeks apart, of white-oil 

 emulsion, or a combination of oil emul- 

 sion and nicotine sulfate (p. 101). 



