38 
BULLETIN 1374, U. S. DEPARTMENT OF AGRICULTURE 
district (fig. 2, p. 3), whereby the fields remain under water for 
periods varying from one to two months and sometimes longer, 
will kill very nearly all the resting larvae in the soil and in bolls on the 
surface. The flooding of heavily infested cotton fields just cleared, 
whenever it can be practiced, should materially retard the infestation 
in new cotton. 
WINTER PLOWING 
To determine the effect of winter plowing on resting larvas in the 
soil, an experiment was conducted in 1922 in which plats in a field 
that was heavily infested with the pink bollworm late in the fall of 
1921 were plowed in different ways. Five quarter-acre plats were 
laid off and the following treatments given: 
Plat 1: Uncultivated. 
Plat 2: Harrowed and cross-harrowed with disk harrow, March 9, 1922. 
Plat 3: Plowed to a depth of about 6 inches, harrowed and cross-harrowed 
with disk harrow, March 9, 1922. 
Plat 4: Plowed to a depth of 6 inches, March 9, 1922. 
Plat 5: Zoca, soil thrown awav from plants with two cultivator shovels, 
first week of April, 1922. 
After this plowing, examinations of 1 square yard of soil to the 
depth of about 8 inches were made in each of these plats at intervals 
of about 20 weeks. Plat 5 was not included in the first examination, 
as it had not then been cultivated. The data obtained in this 
experiment are given in Table 29. 
Table 29. — Effect of different methods of plowing on the pink bollicorm hibernating 
in the soil 
Number of pink bolhvorms found per square yard of soil 
Date examined 
Plat 1, check 
Plat 2, har- 
rowed 
Plat 3, plowed 
and harrowed 
Plat 4. plowed 
only 
Plat 5. culti- 
vated 
Mar. 22- 
1922 
Apr. 17- 
May 1. 
17. 
30- 
June 12. 
26. 
July 10. 
24. 
Aug. 8.. 
Total 
Average 
Percentagi 
dead 
Living Dead Living Dead ' Living [ Dead Living Dead Living i Dead 
49 
43.0 
11 
3 
7 
1 
2 
13 
4 
7 
4 
6 
2 
2 
3 
4 


32 
3.2 
33 
3.3 
36 
.30. 
30 
3.0 
45.5 
41 
4.1 
X o examina- 
tion. 
2 ■ 1 
1 
2 
1 
3 




19 
1.9 
15 
1.67 
34 
Considering only the total number of living individuals found per 
plat, there is a notable reduction in the plowed plats, especially the 
cultivated zoca. But the two harrowed plats show the highest 
percentage of dead individuals, and plat 4 is particularly low in this. 
Considering the individual examinations, the first one shows a very 
decided advantage for the two harrowed plats. Only 4 and 3 living 
specimens were found in these, compared with 10 in the uncultivated 
