CHAPTER XX 

 ORCHARD PESTS AND THEIR CONTROL 



THE fruit-grower in the semi-arid regions is fortunate 

 in having but few of the many orchard diseases to con- 

 tend with. The writers are of the opinion that this im- 

 munity to disease, so far as the great majority of common 

 troubles is concerned, will be permanent. We are con- 

 firmed in this view for several reasons, among which may 

 be mentioned this point: orchard pests are often spread 

 from one locality to another on nursery stock, pear- 

 blight and crown-gall having been brought to our or- 

 chards in this way. This being true, it stands to reason 

 that many other things have found their way to our 

 orchards, as trees and plants come to us from all sections 

 of the United States. One can only conclude that the 

 climatic conditions are such that many of these common 

 pests of the humid states will not thrive. At any rate, 

 they are not found here, and bordeaux mixture, the stand- 

 ard fungicide, is unknown to most of our growers. Four 

 years ago a few leaves attacked by curl were found on 

 each of six or eight young peach trees in an orchard at 

 Paonia, Colorado. All affected leaves were picked from 

 the trees for safety, but it is scarcely possible that all 

 traces of the disease were removed. The trees have been 

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