r.-i 



NATT'RAT. CONTROL OF THE COTTON BOLT WEEVIL. 



DESTRUCTION OF COTTON FORMS BY WEEVIL ATTACK OR BY 



NATURAL CAUSES. 



It seems advisable in connection witli tliis study of factors con- 

 cerned in the natural control of the boll wee^-il to place on record some 

 of the data which have l)een obtained, showinfj the ])r()])()rti()n of 

 squares and bolls which have l)e(Mi found to be destroyed by wecA'il 

 attack or Avhich were shed by the ])lant from natural causes without 

 insect mjury. 



COLLECTIONS OF FALLEN FORMS IN 1905. 



Durinj^: the season of 1905 quite extensive experiments were made 

 to determine the A^alue of a thorouo:h collection of fallen forms in 

 checkiiig the injur}' done by the weevil. These experiments showed 

 a net loss. The cost of collectino^ fallen forms exceeded by several 

 dollars per acre the slight increase in yield shown by the plots from 

 which collections Avere made as compared with plots under similar 

 conditions, but in which no forms were collected. Xo examinations 

 were matle of these forms to determine the ])rop()rtion which had been 

 attacked by the weevil, but from sample lots as shcnAii in Table XIV 

 the propc^rtion of squares and bolls was determined. 



Table XIY .^Proportion of squares and bolls among fallen fruit, Texas, 1905. 



Locality. 



Date. 



Squares. 



Bolls. 



Total i , 



'SeT Number.' ff^ff^' ! Nun.ber.| g^got 



Gurlev, Tex Aug. 10-12 I 



Do Aug. 17 1 



Do ' Aug. 19 ' 



Do Aug. 31 1 



Quinlan, Te.x ' Aug. 24 j 



Waco Tex i Aug. 31 ! 



2,442 



775 



650 



2.542 



4.036 



Total or average. 



10.943 



147 

 411 

 239 

 240 

 472 

 1.269 



29.5 

 16.8 

 30.8 

 36.9 

 18.6 

 31.4 



2.778 



25.4 



a5i 



2.031 



536 



410 



2.070 



2.767 



70.5 

 S3. 2 

 69.2 

 63.1 

 81.4 

 68.6 



8.165 



74.6 



It should be stated that the lots for which figures are given in 

 Table XIA' were from the last collections made in those experiments. 

 The picking began early in July, and doubtless a test at that time 

 would have sho\\Ti a considerabl}' larger proportion of squares. As 

 it was, the average proportion among the nearly 11,000 forms exam- 

 ined was approximately one square to every three small bolls. In 

 the held at Gurley five collections were made in about six weeks. 

 This work extended over one-half of the 16-acre field. I^pon this 

 8 acres a])oiit 730,000 fallen forms were collected. According to the 

 proportions shown in Table XY, it would seem conservative to esti- 

 mate that in this field at Gurley there were collected fallen scjuares 

 containing from 100,000 to 125,000 weevil stages, and in the fallen 

 bolls from 100,000 to 115,000 stages. From this S acres, therefore, 

 there were collected, during July and August, 1905, in all probability 

 from 200,000 to 250,000 weevil stages. If we apply to this number 



