CHAPTER XXIV 

 SOME INSECTS INJURIOUS TO ORCHARD FRUITS* 



The San Jose Scale f 



PROBABLY the most serious of all the insect pests of the orchard 

 is the San Jose Scale, for it will kill young trees in two or three 

 years, and old trees must be sprayed annually to keep it under 

 control. So insidious is the attack of the pest to those unfamiliar 

 with it that it has killed many thousands of trees before the 

 owners suspected its presence. It may be most readily detected 

 on the fruit, which becomes spotted with small red circles which 

 form around the scales, but usually the fruit is not attacked 

 until the tree is badly infested. On the young twigs and along 

 the veins of the leaves a similar reddish discoloration appears 

 around the scales. The trunk and branches covered with scales 

 have a rough grayish appearance, as if they had been coated 

 with dark ashes. By scraping the surface the soft, juicy, yel- 

 lowish insects will be revealed beneath the covering scales. If 

 a single female insect be examined it will be found that it is 

 covered by a small, circular scale, varying from grayish to blackish 

 in color, formed of concentric circles, the centre of which is quite 

 convex and forms a "nipple," which is yellowish and shining 

 when the surface is rubbed off. If this scale be raised with a 

 pin, beneath it may be seen a small, soft, oval, orange-colored 

 object, which is the true female insect. She is an almost shape- 

 less mass of protoplasm, lacking head, legs and eyes, only the 

 thread-like mouth parts and anal plate being distinct. The scale 

 itself is merely a waxy covering secreted by the insect beneath. 

 The scale of the male is smaller and somewhat elongated, the 

 nipple being at the larger end. 



* See Quaintance and Seigler, Farmers' Bulletin 908, U. S. Dept. Agr. 



^Aspidiotus perniciosus Comstock. Family Coccidce. See C. L. Mar- 

 latt, Bulletin 62, Bureau of Entomology, U. S. Dept. Agr., and the numer- 

 ous publications of many of the experiment stations, listed in his bibliography. 



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