INSECTS AFFECTING PARK AND WOODLAND TREES 



47 



estimate of the relative resistance of these trees to insect attack in New 

 York State, specially in the Hudson river valley. The tij^ure 3 has been 

 placed opposite trees which are practically immune from insect injury, 2.5 

 indicates some damage. Trees having one somewhat serious enemy are 

 rated at 2, antl those having at least one notorious insect pest at 1.5. 

 Greater likelihood of injuries is indicated by i and still more by .5. The 

 species are arranged according to the comparative injury and the list follows : 



Tulip tree 3 



*Tree of Heaven - - - 3 

 Hardy catalpa - - - - 3 



Gingko 3 



Red oak ----- 

 Scarlet oak - - - - 

 Yellow oak - - - - 

 Oriental plane tree - 

 American plane tree - 

 Sycamore maple - - 

 Norway maple - - - 

 Sugar maple - - - 

 White oak . - . - 

 Bur oak 



-o 



2-5 



2-5 

 -•5 



2-5 

 2-5 



2 



Red maple 2 



Honey locust - - - - 2 

 European linden - - 

 American linden - - 

 Horse-chestnut - - - 

 Soft or silver maple - 

 American elm - - - 

 *Hackberry - - - - . 

 European elm - - - 

 Scotch elm - - - - 

 Cottonwood - - - - 

 Balm of Gilead - - 

 Black locust - - - - 



1-5 

 1-5 



1-5 



Those that are starred have been seen only in parks or in such small 

 numbers that the rating can be regarded as provisional only. 



Massing of trees. It is not only advantageous to select trees possessing 

 relative immunity from insect enemies but it is also advisable to avoid plant- 

 ing too many of one variety together. It is a well recognized principle 

 among agriculturists that large areas devoted to a single crop, specially for 

 a series of years, increase the danger from insect enemies and the same 

 applies in the case of shade trees set in parks and along our streets. It would 

 be much better could different varieties be alternated on the same street or 

 at least set in small groups, so that in case a few became badly infested by 

 such a species as the white marked tussock moth, Hemerocampa 



