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MISC. PUBLICATION 62 6, U. S. DEPT. OF AGRICULTURE 



Another leaf roller, Evora hemidesma 

 (Zell.), occasionally injures spirea in 

 midsummer in much the same way as 

 does the oblique-banded leaf roller. 



Treatment. — Same as for the green- 

 house leaf tier (p. 5). 



Spirea Aphid 



About the time the spireas are through 

 blooming the tender shoots of these 

 plants often become infested with the 

 spirea aphid (Aphis spiraecola Patch). 

 These small plant lice may be found 

 clustered along the new shoots, where 

 they suck the plant juices and stunt the 

 tips. The aphids on the tip appear 

 similar to those shown in figure 124. 

 This aphid, which is also called the 

 citrus aphid, is mostly greenish, but as 

 the winged form develops the fore part 

 of the body turns dark brown. Several 

 other aphids also may at times attack 

 the various kinds of spirea. 



Treatment. — Same as for aphids 

 (p. 9). 



Other Pests of Spirea 



Pa?e 



Red spiders . - 11 



Oystershell scale 56 



San Jose scale 57 



Cottony maple scale 47 



SPRUCE 



Eastern Spruce Gall Aphid 



Small conelike swellings, or galls, may 

 develop on the base of the new-growth 

 shoots of Norway and white spruce, and 

 occasionally on black, red, and possibly 

 other spruces. The galls are usually 

 about %-inch long and resemble some- 

 what a miniature pineapple (fig. 143). 

 They are caused by the eastern spruce 

 gall aphid (Chermes abietis L.), which 

 occurs in the eastern half of the United 

 States. Many of the infested twigs die, 

 and the tree may be deformed and 

 weakened by heavy or repeated infesta- 

 tions. Certain individual trees appear 

 to be more susceptible to attack than 

 others. The tiny, bluish-gray, young 

 aphids, or nymphs, spend the winter on 

 the twigs, principally at the base of the 

 buds. In the spring they develop into 

 wingless adults, about Ma-inch long, 

 which become covered with a white 

 cottony secretion and lay groups of eggs. 

 The hatching young begin sucking at the 

 bases of the new needles, causing the 

 needles to swell and form the gall which 

 encloses the insects. In August the galls 

 turn brownish and each cell opens, per- 

 mitting the emergence of the maturing 

 aphids, which soon develop wings and 

 lay groups of eggs on the needles. These 





Figure 143. — Galls of the eastern spruce 

 gall aphid at the base of new-growth 

 shoots. About two-thirds natural 

 size. 



hatch into the young aphids which over- 

 winter near the buds. 



Treatment. — Spray the trees in the 

 spring before the buds begin to swell, 

 taking special care to wet the buds and 

 twigs. A nicotine sulfate-soap solution 

 at the usual strength (p. 97) will give 

 good results if applied on a warm day, 

 and it is safe to use on the trees. A 

 pyrethrum spray would no doubt be 

 equally effective. A soap solution (1 

 pound of laundry or fish-oil soap in 10 

 gallons of water) will often give good 

 results. Lime-sulfur at dormant 

 strength is safe and effective, but it 

 leaves a temporary yellowish deposit on 

 the foliage and will also discolor paint. 

 Miscible oils are also effective but may 

 occasionally injure the needles. A 

 combination of 2-percent white-oil emul- 

 sion and nicotine sulfate (p. 101) has also 

 been reported as satisfactory. Spraying 

 may be done also in the fall (October) 

 after all eggs have hatched, but 

 since many of the aphids die during the 

 winter, spraying in early spring is prefer- 

 able. Where only a few galls occur on 

 small trees, the infestation can usually 

 be controlled by cutting off and destroy- 

 ing the fresh galls by midsummer, be- 

 fore the insects have emerged. 



Cooley's Spruce Gall Aphid 



Cooley's spruce gall aphid (Chermes 

 eooleyi Gill.), also known as the Sitka 

 or blue spruce gall aphid, causes a gall, 

 or swelling, 1 to 3 inches long at the tips 

 of the new-growth shoots (fig. 144). 



