﻿44 



BULLETTlSr 1374, U. S. DEPARTMENT OF AGEICULTUEE 



A field that was heavily infested late in the fall was selected and on 

 November 23, 2 square yards of soil to a depth of 6 inches were 

 examined at each of five different points. An average of 5.2 Hving 

 larv^ per square yard were found in this soil. At the same time all 

 bolls on the stalks growing on these 10 square yards of soil were 

 removed and examined. There was a total of 122 dry and 50 green 

 bolls, an average of 17.2 bolls per square yard, and these contained 

 a total of 397 hving larv^ (first and second instars not included),, 

 or an average of 39.7 per square yard. 



At near-by points in this field two areas of 50 square yards each 

 were staked off on November 25 and the bolls both on the plants 

 and on the ground were counted. On November 28 and 29 the 

 stalks were cut, and on December 1 they were raked up. On the 

 following day the bolls on the surface of the ground in the same 

 areas were again counted. The results are shown in Table 36. 



Table 36. — Number of bolls on stalks and on the ground on an area of 100 square 

 yards, before and after cutting stalks 





Bolls 



Before cutting 



stalks 



After cutting 

 stalks 



Percent- 

 age shed 





On On 



stalks ground : 



On 

 stalks 



On 



ground 



in cut- 

 ting 



Green bolls 



108 ^ 3 

 986 ' 190 i 



177 

 1443 



34 

 733 



28.7 



Open bolls 



55.1 









Total 



1,094 193 



1520 



767 



52.5 









Per cent of total 



15.00 





59.6 















I Calculated. 



This shows that nearly 60 per cent of all the boUs were left on the 

 ground after the fields were cleaned, and that 28.7 per cent of the 

 green bolls and 55.1 per cent of the open bolls on the stalks were shed in 

 cutting the stalks. Using the percentage of 15 for bolls on the ground 

 before cutting and the figure of 17.2 bolls on stalks per square yard 

 already mentioned, at the time the soil examination was made on 

 November 23 there were on an average 3 bolls per square yard on 

 the surface of the soil at the points where these examinations were 

 made. On November 25, 100 bolls collected from the surface of the 

 soil showed an average of 2.12 living larvae per boll, which would 

 make an average of 6.36 hving larvae in bolls on the surface of every 

 square yard of soil. On each of December 2 and 5,100 bolls were 

 collected from the surface of the soil and examined, giving an average 

 of 1.41 hving larvae per boU. And on December 5 another square 

 yard of soil was examined at each of the 5 points where examinations 

 were made before, giving an average of 21.6 hving larvae per square 

 yard in the soil. Then using the figures obtained in these two soil 

 examinations and the percentages given in Table 36, the distribution 

 of larvae before and after the stalks were cut can be calculated. 

 This calculation is summarized in Table 37. 



