CONCLUSIONS. 25 



the early parts of the season before the period of total infestation is 

 reached. 



The planting of the two kinds of cotton side by side insures unfair 

 conditions for the late cotton by breeding an extra supply of weevils 

 close at hand. But if the experiment is made in isolated fields the 

 usual inequalities of infestation may give an unfair advantage to 

 either planting. 



A field of late cotton planted by itself might appear at no such 

 disadvantage in relation to weevil injury as would be expected from 

 experiments with early and late rows planted close together. As a 

 matter of fact, it often happens that a late-planted field suffers less 

 from the weevils than fields a mile or two away that were planted 

 a month or six weeks earlier. 



But as soon as we begin to compare the different fields more in 

 detail it becomes apparent that many other elements may modify 

 our conclusions. More fertile soil or more favorable temperatures 

 that enable the plants to make more rapid and uninterrupted growth 

 may be the cause of a larger yield, instead of any particular factor 

 of weevil resistance that might have been under investigation and 

 that might have very definite importance in another case. In short, 

 the problem of weevil resistance is not to be separated from other 

 complex cultural problems. The factors of weevil resistance have to 

 be studied and applied from the standpoint of the local conditions 

 that determine the choice of varieties and methods of cultivation. 



CONCLUSIONS. 



The presence of the boll weevil introduces another factor of un- 

 certainty into problems of cotton production in addition to the usual 

 differences of soils and seasons. The effects of special methods of cul- 

 ture and the special characteristics of varieties should be taken into 

 account in attempting to grow cotton in weevil-infested regions. 



Weevil-resisting characters and methods of cultivation are more 

 useful in dry regions or in dry seasons, because the propagation of 

 the weevils is less rapid and the weevil-resisting factors are effective 

 for longer periods. In dry regions the same factor that restricts the 

 growth of the plants also tends to prevent the propagation of the 

 weevils. In humid regions, on the other hand, the growth of the 

 plants may be impeded by wet or cloudy weather that does not restrict 

 the propagation of the weevils. 



Wet weather not only favors the rapid multiplication of the wee- 

 vils, but also interferes with the application of cultural expedients for 

 avoiding weevil injury. Even the weevil-resistant characters of earli- 

 ness, quick fruiting, and determinate habits of growth are likely to 



220 



