﻿42 



BULLETIN" 1374, U. S. DEPARTMENT OF AGRICULTURE 



If the pink boll worm normally remained in the blooms until they 

 were shed, a considerable number of those in blooms falling between 

 the rows should be killed by the heat of the sun. On September 26 

 some blooms containing larvae were tagged for observation, to ascer- 

 tain whether the larvas remain in the blooms until they are shed. 

 Some of these blooms were removed from the plants each day and 

 examined, with results as follows: 



Sept. 27. 20 blooms removed, 19 contained larvae. 



28. 20 blooms removed, 16 contained larvae. 



29. 20 blooms removed, 9 contained larvae. 



30. 18 blooms removed, 4 contained larvae. 



This shows that normally the majority of the larv^ leave the 

 blooms before they are shed. Thus they may have a better oppor- 

 tunity to seek suitable shelter in the shade of the plants than they 

 would have if they remained in the blooms until they are shed. 



It would appear from the results of the foregoing tests that a method 

 of cultivation during the summer in which the top layer of soil is 

 thrown away from the plants might materially increase the mortality 

 in the soil by exposing larvae and pupae to the sun. An experiment 

 aimed at this point was conducted during the summer of 1922. 

 Four plats of about 12 acres each were laid off and numbered. Plats 

 1 and 4 were checks, and plats 2 and 3 were cultivated every 6 days, 

 plat 2 on 1 day and plat 3 on the following day. Cultivators with 

 shovels set so as to throw the soil away from the plants were used. 

 This work was continued from August 4 and 5 to September 14 and 

 15, a total of 8 cultivations being given each of the plats. When this 

 experiment was begun, regular cultivation had been discontinued, 

 so plats 1 and 4 received no cultivation whatever during this period. 

 A 6-day interval was used between cultivations. This is the min- 

 imum pupal period at this time of the year, according to Loftin ^^ 

 and the purpose was to stir the soil at least once during the time each 

 individual is in the pupa stage. The pupa would not be able to move 

 about to any extent if exposed to the sun by the cultivator. 



A square yard of soil from each plat was examined weekly and a 

 sample of boUs from 2 points per plat every 10 days. The results of 

 these examinations are given in Tables 34 and 35. 



Table 34.- — Effect of summer cultivation on the pink hollworm in the soil 

 [Living and dead larva and pupae and pupa cases in 2 square yards of soil] 





Plats 2 and 3 (cultivated) 



Plats 1 and 4 (check) 



Date of examination 



Living 



Dead 



Pupal 

 cases 



Living 



Dead 



Pupal 

 cases 



Aug. 8 





1 

 3 



7 

 12 

 11 

 20 



5 





1 

 1 

 9 

 14 

 10 

 19 

 3 







15 - 











22 



3 



18 

 5 



15 



7 



1 



16 

 10 

 19 



24 

 2 





29 



3 



Sept. 5 



1 

 4 

 3 



4 



12 



7 



21 



1 







Total. 



48 



59 



9 



57 



71 



15 







Total 





116 



50.9 





143 





Percentage dead 



49.6 















13 U. C. Loftin, K. B. McKinney, and W. K. Hanson. Op. cit. 



