SUMMARY AND CONCLUSIONS. 73 



SUMMARY AND CONCLUSIONS. 



If there be a fair amount of moisture in the soil up to the time squares 

 begin to form, and there then ensues a period of from four to six weeks 

 of hot dry weather, with mean average temperatures ranging from 75 

 to 85 degrees F., it may be expected that the weevils, though abundant 

 theretofore, may be so effectively checked as to do little injury to the 

 crop of that season. 



An entire season of extreme drought, even without exceptionally 

 high temperatures, will greatly reduce the number of weevils, but the 

 crop will be small because of the continued lack of moisture. This 

 condition may show little benefit from weevil control during that sea- 

 son, but will greatly favor the production of a large crop, if weather 

 conditions be favorable, during the following season. The difference in 

 effect of a drought during squaring season alone and during the entire 

 season lies in the widely different effect which those conditions exert 

 upon the number of weevils developed in the fall, upon the food sup- 

 ply available to the weevils until time for them to enter hibernation, 

 and upon the shelter obtainable by the weevils during winter. In 

 the former case many weevils may survive, in the latter few weevils 

 will survive to attack the succeeding crop. 



Winter conditions of unusual severity with frequent low tempera- 

 tures and much rainfall have a beneficial effect by reducing the num- 

 ber of weevils surviving hibernation and by preventing the survival 

 of old cotton roots. 



By cultural practices it is possible to secure regularly as great 

 reduction in weevil injury during the following season as occurs 

 occasionally after winters of extreme severity. 



Defoliation of cotton by the cotton leaf worms, if thorough and 

 repeated, may be a very important factor in reducing the number of 

 weevils in a field which may enter hibernation, or which are likely 

 to survive. The planter can usually secure regularly much of the 

 good effect of irregular leaf worm defoliations by destroying the 

 cotton stalks early in the fall. 



Fallen forms contain fully 70 per cent of the weevil stages develop- 

 ing in a field. These stages are exposed to the most effective action 

 of heat and of ant attack. Only in case of the fallen forms is it pos- 

 sible to vary cultural practice so as to increase the effectiveness of 

 these factors. The mortality occurring in fallen forms is fully four 

 times as effective in controlling the weevil as is that in hanging forms. 



Less than one-half of all the weevil stages were still alive when 

 found. If these had been allowed to remain undisturbed, under the 

 continued influence of the three factors of natural control studied, it 

 is very probable that the total mortality resulting would finally have 



