INSECTS 171 



insect appearing as a casual invader upon fruit trees may become 

 a serious pest by reason of scarcity of its natural food plant. During 

 a period of minimum production of a given species, some insect 

 which has accepted that species as its food may be driven to seek 

 sustenance elsewhere and is likely to find its wants met by foliage 

 or fruit of some crop plant. 



The clearing away of a timber tract may result in serious depre- 

 dations upon neighboring orchards by insects whose natural food 

 plants have thus been destroyed. When a native insect leaves 

 a wild food plant and finds an acceptable substitute in leaves or 

 fruit of orchard trees, it enters upon a new career and is likely to 

 push rapidly to a maximum in numbers because of the abundance 

 of food at hand. When the apple curculio and the dreaded rail- 

 road worm, which originally fed on the wild hawthorn, and the 

 flat-headed borer, which lived in the oak, were forced by the 

 decrease of their natural food plants to substitute cultivated fruits 

 and fruit trees, they solved their own food problem, but in so do- 

 ing laid a heavy burden upon the fruit-grower. They have become 

 real pests and, while held more or less in check by natural enemies, 

 must be seriously considered in fruit-growing operations. 



From the little that has been said it should be evident that 

 attention must be given to all insect injuries that may be dis- 

 covered on tree or fruit, no matter how slight or infrequent they 

 may be. Establish the connection between the injury observed 

 and the insect that does it ; learn the habits of the insect, its 

 period of work, and all facts possible regarding its history ; or 

 take the safe and more expedient course of sending the insect and 

 a specimen of its work to an entomologist for determination and 

 information regarding its history, its standing as an injurious 

 species, the probabilities of its becoming seriously destructive, and 

 the most efficient remedies. File this information for easy access 

 when the time of need comes. 



The discussion of the insects affecting the apple will be subdi- 

 vided according to the parts of the tree. 



1 . Those affecting woody parts. 



2. Those affecting leaves. 



3. Those affecting blossoms. 



4. Those affecting fruit. 



