APPENDIX. 361 



THE SAN JOSE SCALE. 



By Profs. L. O. Howakh and C. L. Mari.att. 

 HABITS AXI) JLIFE-HISTORY. 



NATURE OF THE DAMAGE. 



The San Jose scale, as already stated, occurs on all parts of the plant, 

 limbs, leaves, and fruit. As the plant becomes badly infested the scales lie 

 very close together on the limbs, frequently ovei'lapping, sometimes with 

 i^everal young ones clustering over the surface of an old mature scale. The 

 general appearance which they present is of a grayish, very slightly rough- 

 ened, scurfy deposit. The natural rich reddish color of the young limbs of 

 peach, pear, and apple is quite obscured when these trees are thickly in- 

 fested, and they have then every appearance of being coated with ashes. 

 When the scales are crushed by scraping, a yellowish, oily liquid will ap- 

 pear, resulting from the mashing of the soft yellow insects beneath the 

 scales. Examined under a hand lens during the summer numbers of the 

 little orange-colored larvae will be seen running about, and the snowy white 

 ,young scales will be interspersed with old brown or blackened mature 

 scales. The appearance presented at this time under the lens is shown in 

 the frontispiece and still more satisfactorily in the accompanying figure 

 ( Fig. 2 ). Very frequently the scale has a marked tendency to infest the 

 extremities of the branches and twigs. This is particularly noticeable with 

 pear. As usually found on peach the sale is massed often more densely on 

 the older growth and works out more slowly toward the new wood. 



The leaves are much less apt to bear scales, but in severe cases the upper 

 .surface particularly becomes infested, the scales frequently ranging in two 

 or more quite regular rows on either side of the midrib. The male scales 

 are more numerous on the leaves than the females. The infested leaves 

 turn purplish brown. 



The San Jose scale was formerly supposed to differ from all others in the 

 peculiar reddening eflfect which it produces upon the skin of the fruit and 

 of tender twigs. This, however, sometimes occurs with other scales, but is 

 a particularly characteristic feature of this insect, and renders it easy to 

 distinguish. The encircling band of reddish discoloration around the margin 

 of each female scale is very noticeable on fruit, especially pears. This 

 appearance, however, sometimes so closely resembles the small spots on 

 fruit produced by a common fungus, Entomosporium maculatum Lev., as to 

 require close examination with a lens to distinguish it. Fruit severely 

 attacked becomes distorted, rough, and pitted, frequently cracking, and 

 may eventually fall prematurely, or at least become unmarketable. 



The cambium layer of young twigs where the scales are massed together 



