56 



begin developiiiciit. In the order of their general im- 

 portance and with the average percentage of mortality 

 caused by each, they are as follows. 1. Climatic con- 

 ditions (especially heat and drought in summer), 25 

 per cent.; (2) Predacious insects ("fire ants" princi- 

 pally), 16 per cent.; (3) Plant resistance by prolifera- 

 tion. 12.5 per cent.; (4) parasites, 4 per cent. Naturally 

 the mortality from heat and predatory ants is greatest 

 among squares and small bolls which fall to thu 

 ground. These constitute about seven-eighths of the 

 total nund)er of infested forms. The work of parasites 

 is greatest among the small portion (one-eighth) of 

 forms which remain hanging, but dry up, upon the 

 plant. 



These Factors Affect Weevil Iiijiiry. — As a direct 

 result of the varying influence of these factors in dif- 

 ferent sections and during different seasons in llu' 

 same locality, the direct injuriousness of the boll wei- 

 vil varies quite widely. Climatic factors affect the 

 growth of the cotton plants as well as the development 

 of the weevils. Conditions of frequent and heavy 

 rainfall, with high humidity and warmth, produce 

 naturally the maximum vegetative growth of cotton, 

 or the largest weed, and also the maximum number of 

 weevils with their consequent maximum direct injury 

 to the cotton yield. Under such conditions the cotton 

 crop is almost certain to be a failure. On the other 

 hand, with a rainfall in June and July especially of 

 less than four inches per month, and if good cultural 

 conditions are maintained so that the plants may con- 

 tinue fruiting steadily, there should be no serious doul)t 

 of the possibility of raising a very good crop of cotton 

 in spite of the weevils. 



Summer Control by Heat and Drought. — Long peri- 

 ods of extreme heat and drought occurring early in the 

 fruiting season are most effective in checking the mul- 

 tiplication ol the weevils. To exert a very marked 

 •effect this period must extend beyond four weeks with 

 maximum lemperatures, as recorded by the Weather 

 Bureau, nuiging above 90 degrees much of the time. 

 During the lirst month or six weeks after squaring be- 

 gins, the plants do not shade the ground very nuich and 

 weevil stages in fallen squares and small bolls may 

 be more certainly destroyed by heat and drying than 

 will be the case later in the summer when the ground 

 is more completely shaded. This matter is quite fully 



