THE GEOGRAPHY OF FRUIT GROWING 



633 



OTHER FACTORS INFLUENCING THE GEOGRAPHIC DISTRIBUTION OF 



FRUITS 



Sunshine. — The amount of sunshine to which the trees are exposed 

 during their growing season is perhaps of secondary importance in deter- 

 mining the character of the fruit industry that may develop in different 

 sections, since it nowhere becomes so reduced as to be permanently a Hmit- 

 ing factor. However it is often decisive in determining the varieties that 

 can be grown to advantage. This is true at least in the apple in which 

 coloration depends directly on the relative amount of sunshine that reaches 

 the fruit during the ripening season. Thus the data in Table 9 suggest 

 why it is practicable to grow varieties like Winesap at Grand Junction, 

 Col. and in eastern Washington, but not in the vicinity of Portland, 

 Ore. 



Parasites. — The prevalence of certain parasites is another factor of no 

 mean importance in determining the geographic distribution of fruit 

 growing — at least in determining what kinds of fruit shall be grown 

 in different districts. For instance, European grapes are not grown in 

 the southeastern United States on account of the prevalence there of the 

 grapevine phylloxera and the downy mildew. European plums are 

 commercially unimportant in the Middle West on account of the brown 

 rot and the black knot. Perhaps in the last analysis certain insects and 

 diseases are particularly troublesome in certain districts because they 

 find there temperature and humidity conditions that are especially favor- 

 able for their development and spread ; hence fundamentally it is temper- 

 ature or humidity that really sets limits for these fruits. Nevertheless 



