BOLL WEEVIL CONTROL BY USE OF POISON. 11 



Mississippi. Here the plantations are fairly large, usually involv- 

 ing at least 500 acres of cotton in a single organization and fre- 

 quently a much larger area than this. Under such conditions the 

 poisoning is conducted upon the heavily infested fields with a two- 

 fold object: (1) To secure a reduction in weevil injury upon such 

 fields, and (2) to reduce the numbers of weevils to the point where 

 they will not migrate to the adjoining cotton. It has been found 

 that by operating under such a system it is practically never neces- 

 sary to poison the entire acreage. Complete economic control of 

 the weevils for the entire acreage can be secured by concentrating 

 or, the most heavily infested cuts early in the season and thus pre- 

 venting weevil multiplication and migration. This is particularly 

 advantageous in that it distributes the cost of poisoning over a much 

 wider area than would otherwise be the case. On the other hand, 

 this system has the disadvantage, which will be discussed later, of 

 requiring a rather complicated organization for conducting the 

 poisoning work. 



In districts where the cleared areas are smaller, or farther South 

 where the weevil mortality is so low during the winter that hiberna- 

 tion is possible practically throughout the fields, a more generally 

 distributed infestation is found early in the season and it becomes 

 necessary to treat all fields alike. This is especially true in districts 

 of small farms where the fields are comparatively small in extent and 

 are more or less surrounded by weevil hibernation quarters. Under 

 such conditions the only safe method of procedure is to poison the 

 entire area alike, and this naturally requires a larger amount of 

 poison per acre than is the case where it is necessary to poison only 

 a portion of the crop. 



TIME OF STARTING POISONING. 



Many studies have been conducted upon the subject of determining 

 che proper time for starting poisoning, but so far no thoroughly sat- 

 isfactory simple method has been devised. In order to secure uni- 

 formity, in studies conducted during the past, a system of what is 

 termed " percentage of infestation " has been utilized. This means 

 the percentage of squares present in the field which are weevil-punc- 

 tured. While this is fairly simple of determination, a certain amount 

 of care is required if false conclusions are to be avoided. The method 

 utilized throughout this work has been to examine a hundred or 

 more squares at several points in a field — usually the four corners and 

 the center, although this is not generally necessary under ordinary 

 farming conditions. The percentage of these squares which are 

 weevil-punctured is noted and serves as a basis for the poisoning op- 

 erations. In this connection, however, it should be noted that weevil 



