PINK BOLLWORM OF COTTON IN MEXICO. 



27 



Table XII. — Results of experiment to determine damage caused by feeding of the pink 

 boll worm in the blooms of cotton. 



Blooms. 



Number 

 of tags. 



Dropped 

 off. 



Set bolls. 



Per cent of 

 blooms 

 dropped. 





343 

 343 



140 

 232 



203 

 111 



40.8 





67.6 







From the above table it will be seen that 40.8 per cent of the normal 

 blooms did not set bolls, but 67.6 per cent of the infested blooms did 

 not set bolls, a difference of 26.8 per cent. Granting that under 

 favorable conditions the natural tendency of the plant will be to 

 reset these fruits, it is obvious that 26.8 per cent of the blooms will 

 make bolls at a much later date than they normally would, thereby 

 subjecting them to a far heavier infestation, hence a greater amount 

 of damage. The later maturity of the crop due to shedding of the 

 early squares would also greatly increase the damage by the boll 

 weevil in countries where this insect is present. (See Table XI 

 on "Progress of infestation. ") 



The rate of monthly increase of the infested blooms in a given 

 field is shown in Table X. 



DAMAGE TO BOLLS. 



In estimating the damage caused to the mature bolls (PI. I), 

 pickable as well as nonpickable cotton must be considered. By 

 pickable cotton is meant cotton that is picked, ginned, and marketed 

 from the beginning to the end of the crop; by nonpickable cotton, 

 the bolls or portions of bolls that are left on the plants as unfit for 

 picking, due to damage by the pink bollworm. 



PICKABLE COTTON. 



To arrive at a conclusion as to the extent the cotton taken from 

 the fields is damaged, a 100-pound sample of seed cotton was taken 

 from each picking in each experimental field. These samples were 

 taken by picking all the open cotton on about every twentieth 

 plant in each row, in this manner obtaining as nearly as possible a 

 composite average sample of the cotton open in the field on that 

 date. After the sample was taken the remaining open cotton was 

 picked in the customary manner, thereby guarding against the 

 possibility of mixing any of the first and second pick cotton in the 

 taking of the later samples. 



The samples were stored until the end of the season and then 

 ginned separately, using a small 10-saw sample gin. A gin sample 

 of approximately 2 pounds of lint and a sample of seed weighing 

 about 2 pounds were taken from each of the field samples at the 

 time of ginning. 



