STUDIES OF THE PINK BOLLWORM IN MEXICO 
25 
In November and December of 1921, Schutz and Haskell of the 
Bureau of Markets and Crop Estimates of the United States Depart- 
ment of Agriculture made a survey of the Laguna district, to obtain 
data on the economic phases of the pink bollworm situation. By the 
use of questionnaires they obtained from plantation owners and 
managers data on the average loss due to the pink bollworm. From 
a total of 143 estimates of the losses during the period from 1915 
to 1921, inclusive, they obtained an average yearly loss record of 23.4 
per cent of the crop. Their averages were 22.4 per cent for 1921 
and 30.4 per cent for 1920, based on 39 and 36 estimates, respectively. 
CONDITIONS AFFECTING DAMAGE 
SUMMER IRRIGATION 
Cotton in the Laguna district which receives summer irrigation is 
usually more severely damaged by the pink bollworm than unirri- 
gated cotton. The irrigation causes later fruiting, and this late crop 
becomes subject to attack at the time of the season when the pink 
bollworm is most abundant. Table 19 shows the progress of the 
infestation in irrigated and unirrigated fields in both 1921 and 1922. 
Table 19. — Average 
number of 
worms per green 
fields 
boll in irrigated 
and un 
irrigated 
1921 
Date 
1922 
Date 
Irrigated 1 
Unirri- 
gated 
Irrigated 
Unirri- 
gated 
July 24 
0.33 
.27 
.43 
1.22 
1.81 
2.81 
4.37 
3.92 
5.37 
6.36 
0.57 
.45 
.30 
2.34 
2.27 
3.63 
4.08 
3.54 
5.20 
6.16 
June 27. 
July 8. 
18. 
28. 
Aug. 7. 
17.. 
27.. 
Sept. 5.. 
16.. 
27.. 
0.14 
.18 
.38 
.36 
.60 
1.85 
5.05 
6.87 
2 8.32 
2 5.50 
0.03 
Aug. 2. . 
.02 
9 
.11 
16. . 
.14 
23 
.27 
30 
.77 
Sept. 6 
2.95 
13. . 
4.55 
20. 
27. . 
2.69 
2.85 
1.93 
1.10 
Dates of irrigation: 1921, July 24; 1922, July 11. 
2 Not included in average. 
According to these records the unirrigated cotton in the first part 
of the season of 1921 was a little more severely infested than the 
irrigated, but the condition became reversed in the latter part of the 
season, with a smaller percentage difference. In 1922 the irrigated 
cotton showed a heavier infestation throughout the season. 
A few plantations in the Laguna have wells which supply summer 
irrigation water. Their irrigation practices differ from those on other 
plantations in that less water is applied in the fall and winter flood- 
ings and several irrigations are given during the summer. Planta- 
tions Nos. 16 and 27 in Table 17 are irrigated in this manner. An 
unusually low figure for the nonpickable cotton on plantation No. 27 
is shown in 1921 and 1922. The figure for plantation No. 16 for 
1922, however, is not unusually low. Possibly the low damage on 
the former was due to early maturity of the crops as a whole caused 
by timely irrigations, which prevented the usually very definite sepa- 
ration between the first and second crops found in fields that receive 
late irrigation of river water. 
6077&— 26f 4 
