ORNAMENTAL PLANTS 283 



types of injurious insects are as follows : plant lice, scales, borers, fruit- 

 eating insects, root-feeding insects, and leaf or bud-feeding insects. 

 The leaf or bud-feeding insects are the most harmful to the appearance 

 of ornamental plants, though borers and scales do a vast amount of 

 damage. Plant lice also, during some seasons of the year, spoil the 

 appearance of some ornamental plants as well as do damage. 



Much valuable study and thought have been given to the subject 

 of eradication of insect pests and the information available on this 

 subject is very complete. The spray calendars published by the 

 State Experiment Stations should be consulted for details of how to 

 keep ornamental plants clean and thrifty. 



LIST OF ORNAMENTAL PLANTS SUBJECT TO DISEASE AND 



INSECT PESTS 



Not all trees are equally seriously affected by insect pests and in the 

 list below where a long list of insects and diseases are given after a plant 

 name it does not signify that all those insects and diseases commonly 

 occur, but merely that they are known to occur on one or more species 

 of the genus. The list is given merely as a guide showing along what 

 lines to look for further information, and it also indicates the sort of 

 treatment required as outlined in the chapter on Maintenance, under 

 the spraying discussion (See Page 75). 



Considerable study throughout New York and Ohio in regard 

 to the immunity of trees from insect injury points to the following con- 

 clusions: The arborvitae, tree of heaven, and the ginkgo are practi- 

 cally immune from injurious insects. The American and Oriental 

 planes, the red and scarlet oaks, and the tulip tree and junipers are 

 occasionally attacked. The red, Norway, sugar, and sycamore maples, 

 the white and bur oaks, the honey locust, catalpa, the birches, the 

 spruces, and the white pine have each one serious insect pest. Among 

 the trees very likely to be attacked by insects are the European and 

 American lindens, the American and the water or red elms, the soft 

 maple, the horse-chestnut and buckeyes, and the hackberry. The 

 European and Scotch elms and the willows are very seriously injured 

 by insects, while the yellow locusts and poplars and cottonwoods are so 

 seriously injured as to make it doubtful whether they should ever be 

 used in ornamental planting. 



In the following alphabetical list of plants all the defoliating larval 

 forms of insects are classed as caterpillars for the sake of brevity, and 



