1913.] PUBLIC DOCUMENT — No. 31. 83 



had been used extensively on trolley tracks injury to trees was 

 suspected. 



Other Injurious Factors. — Arsenate of soda, potassium 

 cyanide and other chemicals are extremely poisonous to trees, 

 and when placed in holes bored in the tree the two first named 

 will soon cause death. Since arsenate of soda is often used as 

 a weed killer, it is recommended that care be taken in applying 

 it aroimd the feeding roots of trees. 



A quite common opinion among lino-men is to the effect that 

 copper spikes driven into trees will kill them, but a small maple 

 so treated by us a few years ago showed no abnormal symptoms. 



The foliage of different trees is often injured by spraying 

 with various fungicides and insecticides. It is well known that 

 plum and peach foliage is quite susceptible to this type of in- 

 jury, and even the leaves of maples and other trees may be in- 

 jured by arsenate of lead. The extent of the injury depends 

 not only on the nature of the spraying solution or mixture used, 

 but also on the condition of the foliage sprayed. We have ob- 

 served injury to maples from the use of 12 pounds of arsenate 

 of lead to 100 gallons of water, and Paris green, owing to its 

 present-day uncertain composition, often burns foliage. 



Burning insect nests with torches, although a common prac- 

 tice, is a bad one, and invariably causes injury. Serious harm 

 often results from burning leaves and grass around trees ; and 

 the roots of forest trees, which are often close to the ground, 

 are sometimes injured by burning the imderbrush. 



In conclusion it might be said that in any treatment of trees 

 one should always have before him some definite object; he 

 should leave strictly alone the numerous irrational methods 

 constantly being advocated, and apply to them first the measur- 

 ing stick of common sense. 



