334 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



The host plants of importance here are quite different from those 

 encountered in the forest. The pines and firs have been mostly- 

 replaced by a great variety of broad leaved deciduous and evergreen 

 trees, some of which are natives, while the majority are gathered from 

 various parts of the globe. With this importation of shade and 

 ornamental trees have come some of our worst shade tree as well as 

 fruit tree pests. 



Probably a greater variety of insects is encountered on shade trees 

 than on any other class of trees or plants. Many of the pests of 

 deciduous fruits, nut, olive and citrus trees, berry vines, nurseries 

 and greenhouses are met with, besides a large array which are peculiar 

 to forest and shade trees only. 



The harboring of pests on shade trees, which are also common to 

 different kinds of fruit trees, causes an important relation between the 

 two. This is particularly true in southern California, where a number 

 of towns have spread out into the citrus districts, taking shade trees 

 with them, and on many large estates the beautiful homes are sur- 

 rounded by a wealth of trees and shrubs, which in turn are surrounded 

 by citrus orchards. Fumigation and spraying are practiced in the 

 orchards for the control of scale insects, but not to any large extent 

 upon the shade trees, thus leaving a bountiful supply for reinfestation. 



The Argentine ant is probably the main factor in transporting 

 the scale insects from one tree to another, as well as protecting them 

 from their parasites, and thus becoming a pest to be contended with 

 in the control of shade tree pests. The ant is also a pest from another 

 standpoint in that it thrives and multipHes upon the honej^dew from 

 scale insects infesting shade trees, and from here makes detested inroads 

 into the pantries of nearby houses. This is a problem to be reckoned 

 with especially during these days of food conservation. 



Artificial control of insects on shade trees is greatly neglected. 

 Most farmers now realize that such control is necessary for the main- 

 tenance of healthy fruit trees and the production of clean fruit. A 

 great many people, however, believe that a shade tree should always 

 be able to take care of itself. Therefore, one of the problems is to 

 educate the people into seeing that spraying is necessary at times to 

 maintain a healthy and vigorous shade tree. 



If trees and shrubbery were placed farther apart, and if each indi- 

 vidual tree were thinned out in the top a bit, not the way the tops 

 are often slashed by telephone linemen, but by proper cutting, thus 

 letting in the sunshine, much of the need of spraying would be obviated. 

 This has been demonstrated in Pasadena. There the pepper trees 

 were badly infested with black scale until they were systematically 

 opened up to the sun, whereupon very little spraying became necessary 

 and that only about the lower part of some of the trees. 



