25 



insect standpoint may be seen at a glance the same trees have been 

 rearranged in a separate table as follows: 



Variety of tree. 



Gingko ( Gingko biloba) 



Tulip tree (Liriodendron tulipifera) 



Sugar maple {Acer sa£charum) , 



iRed oak {Quercus rubra) , 



Tree of heaven {Ailanthus glandulosa) . . 



^ Scarlet oak ( Qwercws coccinea) 



Yellow oak ( Quercus velutina) , 



Willow oak ( Quercus phellos) 



Black maple {Acer nigrum) 



Japanese sophora {Sopluyrajaponica) . . 

 Horse-cliestnut (^Escwius hippocasta- 



num) 



Red maple {Acer ritbnim) 



Small-leafed linden ( TUia microphylla) 



White oak {Quercus alba) 



Sweet gum {Liquidambar styradfiua) . . 



Bur oak {Quercus macrocarpa) 



Kentucky coffee tree {Oymnocladue 



dii^isus) 



Sycamore maple {Acer pseudo-plcUanus) 



Insect 

 rating. 



3.0 

 3.0 

 2.5 

 2.5 

 2.5 

 2.5 

 2.6 

 2.5 

 2.5 

 2.5 



2.0 

 2.0 

 2.0 

 2.0 

 2.0 

 2.0 



2.0 

 2.0 



Variety of tree. 



Shingle oak ( Quercits inibricaria) 



Slippery elm ( Vlmus pubescens) 



Norway maple {Acer platanoides) 



Hardy catalpa ( Catalpa speciosa) 



European linden ( TUia vulgaris) 



American elm ( Ulmus americana) 



Hackberry ( Celiis ocddentalis) 



Silver-leafed maple {Acer saccharinum) 



Oriental plane tree {Platanus orientalis) 



American plane tree {Platanus ocd- 

 dentalis) 



American linden ( Tilia americana) 



Honey locust {Oleditschia triacanthos) . . 



Scotch elm ( Ulmus montana) 



Cottonwood {Populus monUifera) 



Balm of Gilead {Populus balsamifera v. 

 candicans) 



European elm ( Vlmus campestris) 



Black locust {Pobinia pseudaeacia) 



Box elder {Negundo negundo) 



Insect 

 rating. 



2.0 

 2.0 

 2.0 

 2.0 

 1.5 

 1.5 

 1.5 

 1.5 

 1.5 



1.5 

 1.5 

 1.0 



1.0 

 .5 



.5 

 .5 

 .5 

 .0 



^ This estimate of the red oak and scarlet oak was based largely on the beautiful 

 condition of certain trees growing in the streets of Washington, D. 0. Since the 

 publication of the Yearbook article, however, several of these trees have developed 

 rather serious cases of insect injury. The locust borer {Xyleutea roUnise) has attacked 

 a number of the trees, and although it is not apparently weakening their vitality to 

 any serious extent, still it bids fair to do considerable damage. The trees have been 

 treated by injecting a small quantity of bisulphide of carbon into the burrows and 

 covering the opening with putty. In a few cases the obscure scale {Aspidiotus 

 obscurus) has attacked these trees. It has not as yet killed any branches, but it 

 multiplies as abundantly as its dangerous relative, A. tenebricosus, of the maple, and 

 I see no reason why it should not be an equally injurious species. This experience 

 somewhat shakes the confidence of the writer in his estimate of the rating of these 

 oaks, but not to any very serious extent. 



It will be noticed that the trees listed by Mr. Fernow which we find 

 to be most immune are the gingko and the tulip tree. Outside of the 

 grounds of the Department of Agriculture at Washington, and Cen- 

 tral Park, New York, few gingko trees are grown in this •countrj'^, 

 except as occasional isolated examples. The tree itself is a very 

 beautiful one, and singularly free from insect attack. In the long 

 double row of these trees, now nearly twenty-five years old, on the 

 grounds of the Department of Agriculture, but one species of injuri- 

 ous insect has ever been found, and the work of this species is very 

 insignificant. It is the little sulphur-yellow leaf-roller, Tortrix sul- 

 phurea/na. 



The tulip tree, which is given the same rating, is, for practical pur- 

 poses, almost as exempt as the gingko. Of late years in the District 



