22 BULLETIN 838, U. S. DEPARTMENT OF AGRICULTURE. 



The common privet {Ligustrum vulgare Linn.) forms an admirable 

 hedge. The holly-leaf cherry {Primus ilidfolia Walp.), Atriplex 

 canescens James, and Plttosporum spp. also are recommended. Pit- 

 tosporum, however, is subject to attacks from scale insects which are 

 just as difficult to control as the cypress bark scale. The Oriental 

 and Italian cypresses form quite effective coniferous hedges, the lat- 

 ter being tall and slender. Certain forms of red cedar (Jtmiperus 

 virginianm Linn.) are used as trimmed hedges in certain sections of 

 the United States. If this proves to be immune to the scale insect, 

 it should be a very good substitute for the Monterey cypress. 



SUMMARY. 



The main cause of the browning and death of so many cypress 

 trees, hedges, and windbreaks throughout California is the cypress 

 bark scale, EhrJwrnia cupressi. 



It was found in the course of a thorough investigation that the 

 scale insect was not a native of the Monterey cypress, but of the 

 incense cedar which occurs in the mountains of California, Nevada, 

 and southern Oregon. From this host it has probably spread to 

 the Monterey cypress by the transportation of incense-cedar seedlings 

 or rustic timber to the regions infested. 



The characteristic injury caused by this insect begins to show on 

 one or two limbs and slowly spreads to the rest of the tree. The 

 foliage turns first yellow, then red or brown, giving the tree a very 

 dilapidated appearance. After a few years the whole tree dies. 



The food plants of the cypress bark scale are Monterey cypress, 

 Arizona cypress, Guadalupe cypress, and incense cedar. 



The larvae are small oval bodies, pale yellow in color, which are 

 active for a short time after hatching. They attach themselves in 

 crevices of the bark and are soon enveloped in a white cottony secre- 

 tion. As they reach maturity they become reddish -brown in color 

 and nearly spherical in shape. 



Oviposition begins in the spring and lasts throughout the summer. 

 The eggs hatch into larvae in less than an hour and soon attach 

 themselves. The females reach maturity in the fall and hibernate 

 over the winter, starting oviposition in the spring. The males ap- 

 pear in the late fall or early winter to mate and die. 



There are several insects which prey upon the cypress bark scale, 

 none of which, however, is abundant enough to control the scale 

 insect. Consequently remedial measures have to be adopted. A 12^ 

 per cent solution of a high-gravity miscible oil is the spray recom- 

 mended. To obtain complete control it is necessary to spray twice 

 in the early fall, once in August and once in the latter part of 

 September. 



