THE EUROPEAN ELM SCALE IN THE WEST. 



other ants are known to transport scale insects from one tree to 

 another in order to increase their food supply, and this method of 

 transportation probably applies to this species as well as to others, 

 since it is usually attended by a great many ants. Elms are nearly 

 always planted so close that some of their branches interlace, en- 

 abling the larvae to crawl at will from one tree to another. Thus 

 it is not long before 

 the European elm scale 

 has thoroughly estab- 

 lished itself upon most 

 of the elms in a locality. 



INJURY. 



Thousands of these 

 scale insects sucking 

 the plant juices from 

 the leaves, twigs, and 

 branches (figs. 2, 3) 

 cause considerable in- 

 jury to elm trees. Their 

 effect upon the elm is 

 shown by yellowing and 

 premature dropping of 

 the leaves, stunting of 

 growth, and dying twigs, 

 branches, and entire 

 trees. Their injury is 

 most apparent on young 

 trees, which occasionally 

 they kill. Mature trees 

 are seldom killed. 



A less serious trouble 

 is the production of a 

 considerable amount of 

 honeydew. which covers 

 the leaves, twigs, and 

 branches, making them 

 black and sticky. It also 

 drops on the street and 

 sidewalk, making the 

 pavement slippery and 

 dangerous to passing ve- 

 hicles, besides having an 

 unpleasant appearance and odor. 

 attrRcted by the honeydew. 



In some sections the American elm is reported as the favorite 

 host of the European elm scale, while in other localities the English, 

 Camperdown, or slippery elm is reported to be the favorite. The 

 American and Camperdown elms seem to be preferred by it in Cali- 

 fornia. Probably the degree of infestation depends upon the con- 

 dition of the tree more than upon any other factor. 



Fig. 2. 



Adult females of European elm scale on elm 

 branch. Slightly enlarged. (Wallace.) 



Many disagreeable insects are 



