REPRESSION. 159 



April 8 and in Louisiana 64 per cent. In Texas, after May 1, in all 

 the experiments, from 4 to 18 per cent of the surviving weevils 

 appeared. In Louisiana, after May 1, from 30 to 40 per cent emerged. 



It is obvious that the fact that many weevils do not appear until 

 long after cotton can be planted and brought to a fruiting stage is a 

 very great advantage to the planter. A portion of a crop at least 

 can be set before the weevils have become active. Usually it is 

 possible to plant a crop sufficiently early to have it set some fruit 

 before much more than 50 per cent of the surviving weevils have 

 emerged. 



Attention was directed to the fact that the development of the 

 weevil is much slower in the early portion of the season than later. 

 For instance, at Vicksburg, Miss., the average period of development 

 in April is 30 days and in May 19 days. In June the period is short- 

 ened to 15 days. Consequently the planter has an opportunity to 

 force the development of fruit on the plants when the weevils are 

 being held in check by the temperatures of the spring months. The 

 ability of the cotton plant to grow during April and May is much 

 greater than that of the weevils. This gives a margin of which the 

 planter can take advantage. 



In the section dealing with natural control it was shown that 

 climatic checks are the most important that the boll weevil experi- 

 ences. The principal manner in which climatic factors affect the 

 weevil is through the drying of the fruit. Naturally, the more heat 

 and light there is to reach the fallen squares, the greater will be the 

 effectiveness of the most important natural means of control. This 

 is the basis for the recommendation that the plants should be given 

 considerable space, not only between the rows, but in the drill. Of 

 course, it would be possible to place the plants entirely too far apart, 

 and thus reduce the yield. There is a happy medium, however, at 

 which planters must arrive from experience on their individual 

 places. At the same time, varieties should be cultivated which have 

 a minimum tendency toward the formation of leafage. 



The work of the insect enemies of the boll weevil is increasing from 

 year to year. This work should be encouraged in so far as possible. 

 It happens that several of the recommendations made for other rea- 

 sons will result in facilitating the work of the enemies of the weevil. 

 This is the case with early planting, wide spacing, and the use of 

 varieties with sparse rather than dense leafage. Even fall destruc- 

 tion is not a disadvantage, because it forces the parasites at the 

 active season to native hosts that carry them through the winter. 

 Wherever possible, varieties should be planted winch retain a large 

 proportion of the infested squares, because the hanging squares are 

 more favorable for parasite attack than those winch fall. 



Whenever the squares are picked by hand they should not be burned 

 or buried, but placed in screened cages. In this way the weevils will 

 be destroyed while the parasites may escape. 



Numerous experiments have shown that a large proportion of the 

 weevils buried under 2 inches of moist soil can not reach the surface. 

 Unfortunately, it is not possible to plow the infested squares under 2 

 inches of sod during the growing season. The operation would 

 result in injury to the root system and cause great shedding. Never- 

 theless it is possible for the planter to follow this practice after 

 maximum infestation has been reached and after the plants have 



