STUDIES OF THE PINK BOLLWORM IE" MEXICO 
37 
REPRESSION 
CULTURAL CONTROL 
The pink bollworm's habit of pupating in the soil during summer, 
and of passing the resting period there to some extent, suggests that 
considerable control may be expected from cultural methods designed 
to kill the larvae and pupae in the soil. 
IRRIGATION 
In the winter of 1921-22 F. F. Bibby conducted an experiment to 
show the effect of flooding on resting larvae in the soil. Heavily 
infested bolls and double seed were placed in a garden under condi- 
tions as nearly as possible representing those normally found in the 
field. The material was arranged in plats part of which could be 
flooded. In these the seed and bolls were buried at several depths, 
one layer in the first inch of soil, another 3 inches beneath the surface, 
and a third 6 inches beneath the surface. A fourth layer was placed 
on the surface of the soil. The latter material floated when water 
was applied. One plat of each, bolls and seed, was flooded for a 
period of 18 days, another for 33 days, and a third for 64 days. 
Each plat was completely covered with water during this entire time. 
The floating bolls were kept in water for periods of 18 and 44 days 
and the seed for 17, 22, 33, and 56 days. 
The data obtained in these experiments are summarized in Table 
28. In preparing this table the average number of living larvae found 
in the seed and bolls when the experiment was started was determined. 
This was considered as 100 per cent and the percentage of living 
larvae and pupae found in later examinations was calculated on this 
basis. Forty-seven days after flooding was discontinued on one of 
the 18-day plats 5 larvae and pupae were found loose in and on the 
surface. 12 
Table 28. — Longevity of resting larvae in bolls and seed in flooded and in dry fields 
Time 
from be- 
ginning 
of treat- 
ment to 
examina- 
tion 
Larvae surviving in bolls and seed 
Approximate date of examination 
Buried from 1 to 6 inches in soil in field 
In dry 
plats 
In plat 
flooded 
18 days 
In plat 
flooded 
33 days 
In plat 
flooded 
64 days 
Floating 
in water 
Dec. 26. 
Days 

20 
40 
60 
70 
90 
100 
110 
149 
159 
Per cent 
100 
Per cent 
100 
Per cent 
100 
Per cent 
100 
Per cent 
100 
17.1 
Feb. 4 
.2 
24. 
7.6 

Mar. 6 
50.9 
1.2 
26.. 
.06 
4.8 
15 
18.4 
May 24 
1.5 
June 3.. 
1.5 
.4 
According to the data gathered in these experiments, the flooding 
of fields in fall and winter, as commonly practiced in the Laguna 
12 According to Willcocks, irrigation causes larva? to leave bolls that are buried and seek the surface cf 
the soil for pupation to a greater extent than they do in dry soil. 
