10 BULLETIN 875, U. S. DEPARTMENT OF AGRICULTURE. 



ture stages developing in the bolls and squares. These immature 

 stages continue developing every day for a considerable period after 

 the application is made. A single application may tremendously re- 

 duce the adult weevils present in the field at that time, but they will 

 be replaced very quiekty by the new generation which is maturing 

 and emerging. Unless the applications are repeated at the proper 

 time intervals, therefore, freshly emerged weevils will soon become 

 sufficiently abimdant to counteract all the benefit which may have 

 been secured from the first treatment. In some cases one or two ap- 

 plications may control the weevils sufficiently to permit the forma- 

 tion of a considerable crop of young bolls, but unless these bolls are 

 protected by continued applications the weevils usually will multiply 

 with sufficient rapidity not only to infest the squares present but also 

 to prevent these young bolls from reaching maturity. 



SEASON FOR APPLICATIONS. 



When it was first found possible to kill at least a certain percent- 

 age of the weevils by poisoning, it seemed that the best results would 

 be secured by early season applications, thus deriving the double 

 benefit of killing the weevils then present and preventing the de- 

 velopment of their potential progeny. Consequently the first tests 

 were almost entirely early season applications. But it was soon found 

 that far more profitable results were secured by treatments later in 

 the season. Thorough studies on this point have since shown quite 

 definitely that by far the greatest profit is derived by making the 

 applications at the critical time when the weevil injury is just begin- 

 ning to exceed the normal shed of the cotton plants. Another im- 

 portant point is that the plant is fruiting so rapidly at this time that 

 every day of retardation of weevil infestation means a great deal in 

 additional cotton production. 



The time when poisoning should begin has almost no relation to 

 the size of the cotton plant and is purely a question of weevil 

 abundance. Such factors, however, as the size of the farm or field 

 involved will determine very largeh' the basis upon which poisoning 

 can be planned. For example, in some districts where the culti- 

 vated areas are large and more or less consolidated, weevil injury 

 is very eventy distributed, owing to the fact that the weevil adults 

 emerging from hibernation in the spring usually concentrate on. the 

 first fields they reach and do not seriously infest the more distant 

 fields until they have practically overtaken the fruiting of this 

 near-by cotton. This condition is found in many portions of the 

 cotton belt and is particularly pronounced in the district where the 

 majority of this Department's tests have been conducted in the past, 

 namely, the Mississippi Delta region of Louisiana, Arkansas, and 



