I 



SPRAYING THE APPLE ORCHARD 63 



is unmodified by liuman action insects are not likely to become ex- 

 tremely injurious becaus'e each species is held in check by some natural 

 means. As soon, however, as an insect's environment is changed by the 

 greater growth of its favorite food plant, the career of the potato beetle 

 is illustrative of this point, or by the destruction of its natural enemies, 

 it is liable to become seriously important in a short time. A comparatively 

 harmless insect in one country, harmless because controlled by its natural 

 enemies, may, on its introduction into another country cause untold dam- 

 age, simply because it finds a more salubrious habitat, and is followed 

 by few if any of its natural enemies. Examples of this class of insect 

 pests are the gypsy moth, San Jose Scale, and many other destructive 

 fruit insects. Unless the natural enemies of these insects are introduced 

 with them or imported later we must fight them artificially by sprays or 

 otherwise. As it is practically impossible to prevent the occasional in- 

 troduction of an insect, these imported pests may be looked upion as one 

 of the prices of our intercourse with other nations. 



The greater prevalence of fungus and bacterial diseases in recent 

 years may be accounted for by the fact that Urge areas in fruit growing 

 districts are devoted to the growing of one kind of fruit and a disease 

 once established in these regions has a large field for spread and 

 development. The prevalence of peach yellows in some peach growing 

 districts is an example of this. Certain of our improved varieties may 

 be less hardy than formerly because the quality of disease resistance 

 may have been sacrificed for other desirable points by the plant breeder. 



To be specific we ordinarily spray the apple in Nebraska for two 

 reasons: 1. To kill the codling moth. 2. To control the apple scab. 



We will first consider the habits and life history of the apple worm or 

 codling moth, which causes more damage to Nebraska apples each year 

 than do all other insects combined. The codling moth is commonly the 

 cause of worminess in the a.pple. Nearly every one has been sur- 

 prised at the pinkis'h white worm at his work near the core, and many 

 of you have wondered where the voracious invader came from and whither 

 he went when his appetite was satisfied and his growth completed. 



While we do not definitely know the original home of the codling 

 moth, it is probably that of the apple. Although there are some re- 

 stricted localities in which the apple is grown that are apparently not 

 yet infested with the codling moth, it can be safely said that the moth 

 is found practically wherever the apple is produced. The insect is dis- 

 tributed naturally by means of flight. As the moth is not naturally a 

 strong flyer, the limit of distribution by this means is three or four 

 miles in a single season. If then, an infested orchard is many miles re- 

 moved from other orchards, as is often the case in the wset, it is neces- 

 sary to look for artificial means of distribution to explain the presence of 

 the codling moth in that orchard. It is extremely probable that the insect 

 was introduced into this country and since its introduction has been dis- 

 tributed mainly by the shipping of affected fruit from the infested regions 

 to those previously uninfested. In this way the insect may be carried 



