HANDBOOK ON INSECT ENEMIES OF FLOWERS AND SHRUBS 57 



Figure 91. — Oystershell scale on a 

 poplar twig. Twice natural size. 



Treatment, — Apply an oil spray in 

 the spring before the buds open, al- 

 though frequently this treatment kills 

 only part of the overwintering eggs. 

 After the young begin hatching, spray 

 several times, at intervals of about 10 

 days or 2 weeks, using a nicotine sulfate 

 and soap solution, a white-oil emulsion, 

 or a combination of the oil and nicotine 

 (p. 101). On shrubs* it is advisable to re- 

 move and destroy the dying and most 

 heavily infested portions before spray- 

 ing. 



San Jose Scale 



Shrubs and trees heavily infested with 

 the San Jose scale (Aspidiotus perni- 

 ciosus Comst.) have the twigs, branches, 

 or stems covered with a grayish layer of 

 tiny, overlapping, waxy scales. Injury 

 by these sucking insects is usually 

 indicated by dead or dying branches, 

 poor vigor, and thin foliage. This scale 

 insect has a wide distribution and is a 

 common enemy of fruit trees. It also 

 attacks many shrubs and shade trees, 

 including ash, dogwood, hawthorn, 

 honeysuckle, lilac, mountain-ash, and 

 rose. The waxy scale covering the 

 female insect is circular, about Vie, inch 

 in diameter, with a slight elevation or 

 nipple near the center, and grayish 

 (fig. 92). The male scale is smaller 

 and more oval. The insects pass the 

 winter in a partly grown condition, and 

 in this stage the scale is nearly black. 

 Growth is completed in the spring, and 



the young are then born alive. From 

 two to six generations may be produced 

 annually, depending on latitude and the 

 length of the active season. 



Treatment. — Since this insect win- 

 ters in a partly grown condition it is 

 more easily killed by dormant spraying 

 than the oystershell scale. Spray with 

 a dormant-strength oil spray or lime- 

 sulfur in the spring before the buds open. 

 A strong soap solution (p. 106) used at 

 this time will give fairly satisfactory re- 

 sults. Prior to spraying, remove the 

 dying and heavily infested portions that 

 can be spared. During the late spring 

 and summer, when the young insects 

 are in the crawling stage, many of them 

 can be killed with nicotine sulfate or a 

 white-oil emulsion. 



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Figure 92. — The San Jose scale: a, 

 Adult female scale; b, male scale; c, 

 young scales; d, larva just hatched; 

 d', same highly magnified; e, scale 

 removed showing body of female 

 beneath. Eight times natural size. 



Giant Hornet 



The giant hornet (Vespa crabro ger- 

 mana Christ) has the habit of gnawing 

 the bark from the smaller branches and 

 stems of shrubs and trees. Irregular 

 patches or rings of bark an inch or more 

 wide may be removed and the brandies 

 girdled (fig. 93). The bark tissue is 

 apparently used in building the nest. 

 Lilac is rather commonly attacked, but 

 birch, boxwood, dahlia, mountain-ash, 

 poplar, rhododendron, willow, and prob- 

 ably others are at times injured. Al- 

 though this European hornet has been 

 in our country for many years, it is still 



