INSECTS AFFECTING OHIO SHADE TREES 171 



Dr. E. P. Felt, in his most excellent work on "The Insects Affect, 

 ing- Park and Woodland Trees," has tabulated the more commoo 

 trees of New York state with relation to their liability to insect 

 attack. As Ohio conditions do not vary to any great extent from 

 those found in New York state, the classification arranged for New 

 York holds good in the main here. Dr. Felt's rating, with a few 

 alterations that will be designated later, is as follows: "The figure 

 3 has been placed opposite trees which are practically immune from 

 insect injury; 2.5 indicates some damage. Trees having one some- 

 what serious enemy are rated at 2 and those having at least one 

 notorious insect pest at 1.5. Greater likelihood of injuries is indi- 

 cated by 1 and still more by .5. The species are arranged accord, 

 ing to the comparative injury as follows: 



Tulip tree 3 Catalpa 2 



*Tree of heaven ; 3 European linden 1.5 



Gingko 3 American linden 15 



Red oak 2.5 Horse chestnut 1.5 



Scarlet oak. I 2.5 Soft or silver maple 1.5 



Oriental plane tree 2.5 American elm 1.5 



American plane tree 2.5 *Hackberry ... 1.5 



Sycamore maple ..2 European elm 1 



Sugar maple 2 Scotch elm 1 



White oak 2 Cottonwood 5 



Burr oak 2 Balm of Gilead 5 



Red maple 2 Yellow locust 5 



Honey locust 2 



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

 bers that the rating- can be regarded as provisional only." 



The above arrangement differs from that of Dr. Felt's list in 

 the position of catalpa, rated by him as 3 and here rated as 2 on 

 account of it's being subject to attack from the catalpa sphinx in 

 the southern sections of the .state and rather generally to the action 

 of the catalpa diplosis (or a closely allied species) working in the 

 tender, growing tips. Also the hackberry and elm are rated .5 

 higher because of the fact that the elm leaf-beetle is not well estab- 

 lished in this state. 



pj Another general principle of correct planting, 



mixed varieties. as brou ht out b Y Dr - Felt > is the undesirability 

 of planting clumps or rows of a single species. 



It may easily be seen that an insect on the hunt for its favorite food 

 plant is much more likely to locate a collection of trees than single 

 individuals scattered here and there. Further, that a 'pest is more 

 easily disseminated when once it becomes established on one of a 

 number of trees of the same variety growing close together, than if 

 the trees were at least alternated with other kinds. 



