INJURY RESULTING TO SCALE [NFESTED TREES. 
15 
to the fruit, as docs also the red scale, resulting in expense for the 
cleaning of fruit in- rendering it of a lower grade and, in extreme 
cases, entirely valueless. 
The black scale, although a much larger insect than either the red 
scale or purple scale, appears to have, generally, little effect on the 
vitality of the tree. Trees severely infested with the black scale may 
appear as healthy as neighboring trees which are clean. Branches 
are seldom if ever destroyed by its attacks alone. 
The commercial importance of the Mack scale arises largely from 
its habit of secreting honeydew, which spreads over the leaves, fruit, 
Fig. 7.— Orange tree show; 
branches at center partly destroyed and stripped of leaves by purple 
scale (Lepidosaphes beckii). (Original.) 
and branches, furnishing a growing medium for a black or sooty-mold 
fungus, resulting in a black coating throughout the tree. This 
coating is removed from the fruit by washing, or in light attacks by 
brushing. In the investigation by Mr. (1. Harold Powell of the 
causes of decay of oranges while in transit from California, it was 
shown that the decay was greater in washed than in unwashed fruit. 
To avoid the washing of fruit ii is necessary to destroy the scale in 
the orchard-. 
a Bui. Ii 1 :;. Bur. Planl Industry, U. S. Dept. of Agriculture, L0O8. 
