August, '19] HERBERT: WESTERN SHADE TREE PESTS 335 



Many shade trees become so large that the question of spraying 

 is not an easy one. A high power spraying apparatus of good capacity 

 has been found practicable for such trees, but this is not always 

 available. Fumigation is often the most satisfactory method of con- 

 troHing certain pests, but again, due to the large size of many trees 

 and the lack of apparatus in all localities outside of the citrus districts, 

 this becomes almost impossible. 



There is not a great deal known here about the proper sprays to 

 use upon conifers and evergreens. What such trees will stand in 

 summer or winter is not very definitely known. This is one of the 

 problems we are working on and hope to solve. 



Washing trees off with a solid stream of water is known to be one 

 of the best remedies for removing many soft bodied scale insects. 

 This is the most feasible means for controlling the European elm 

 scale, particularly on large elms wherever a good pressure of water is 

 available. At least fifty pounds pressure is necessary to give the 

 water enough force to remove the insects. Even with this pressure 

 one needs a travelling platform and an eight or ten foot extension 

 rod in order to get close enough to the scale insects to remove them. 

 With a number of large trees and plenty of available water, it is 

 advisable to use a fire engine and hose if possible, thus obtaining 

 a large head of water under a pressure of 125 pounds or more, which 

 is sufficient to reach all parts of the tree from the ground. One 

 hundred and ninety large trees in San Jose were washed in this way 

 with good success which was more economical than any spraying 

 would have been. 



Some people would rather let a shade tree die than to lift a finger 

 to save it from its enemies, placing more value upon the tree for fire- 

 wood than for any other purpose, while others would pay a great price 

 to save a single tree, realizing that it would take many j^ears to replace 

 it. Thus the question of economy of control does not always enter 

 into a problem. 



The writer has specialized to some extent upon the scale insects 

 infesting shade trees. Below are enumerated some of the more impor- 

 tant of them. 



The European elm scale, Gossyparia spuria (Linn.), mentioned 

 above, is one of our worst pests, occurring in many localities of the 

 west and becoming a disagreeable and harmful pest, causing the trees 

 to become black and sticky, killing limbs and sometimes whole trees. 

 Much of the honeydew falls on the ground, making the streets and 

 sidewalks disagreeable and dangerous to passing horses. 



The cypress l)ark scale, Ehrhornia cupressi (Ehrhorn), is a serious 

 pest in central California upon some of our most popular shade trees. 



