STUDIES OP THE PINK BOLLWORM IF MEXICO 
15 
Bolls of the 1921 crop are still available at the present writing 
(April, 1923), so Table 13 is incomplete, but the records now indicate 
a longevity of over 16 months. 
DAMAGE CAUSED BY THE PINK BOLLWORM 
DAMAGE TO IMMATURE FORMS 
As pointed out by Loftin, 9 the young pink bollworm often enters 
a square and reaches maturity therein without causing shedding, 
and the larva may develop to maturity in the bloom without causing 
abnormal development oi the boll. Just what amount of damage 
the pink bollworm does by feeding on the immature forms on the 
cotton plant is difficult to determine, owing to the usual heavy natural 
shed of forms at about the same time that the pink bollworm becomes 
very numerous. Under conditions prevailing in the Laguna district 
during 1921 and 1922, the damage done to squares, blooms, and very 
young bolls early in the season certainly was entirely negligible 
This point is brought out in Figure 6, in which it will be noted that 
the rapid fruiting early in the season quickly outstrips the multiplica- 
tion of the pink bollworm in the blooms. 
Under normal climatic and cultural conditions in this district the 
fruiting of the cotton is very rapid, once it has well begun. Then a 
point is reached at which, owing to lack of moisture, all young forms 
begin to shed off. Later the cotton makes a second growth, which 
may be very little, or very considerable in case the field receives spring 
or early summer irrigation. This is illustrated in Figure 6, in which 
all records after August 21 represent counts in irrigated fields only. 
The results of observations on the relation of shedding to infestation 
made in a field at Tlahualilo during 1922 are given in Table 14. 
These observations were discontinued early on account of the appear- 
ance of the leaf worm. The table shows the number of forms on 100 
plants on the dates indicated, the number of shed forms found under 
these plants at the same time, and the percentage of these shed 
forms that were infested. The field in which these observations 
were made was cultivated on July 18 and irrigated on July 20. On the 
27th it was again cultivated. Many of the shed forms were therefore 
either covered up or floated away, which made the figure for shed 
forms on July 29 unusually low, and not representative of the entire 
shed since July 14. 
Table 14. — Relation of shedding of immature forms from cotton plants to pink 
bollworm attack, Tlahualilo, 1922 
[Number of forms on and under 100 plants] 
Forms on plants 
Shed forms 
Date 
Bolls 
Squares 
and 
blooms 
Total 
Percent- 
age 
attacked 
by the 
pink 
bollworm 
July 14 
1,586 
994 
947 
712 
49 
11 
834 
488 
132 
10 
12 
36 
212 
3.5 
29. 
2.5 
Aug. 9 
4.5 
16 
1,008 127 

29 
1,038 
1,162 
932 
1,319 
33.3 
Sept. 6 
61.3 
14.. 
69.8 
• U. C. Loftin, K. B. McKinney, and W. K. Hanson. Op. eit. 
