26 
BULLETIN 1374, U. S. DEPABTMEKT OF AGKICULTURE 
DISTANCE FROM COTTON FIELDS OF PREVIOUS YEAR 
On the Tlahualilo plantation a system of rotation is practiced in 
which cotton is not planted on the same land two consecutive seasons. 
In addition a zoning system has been instituted providing the planting 
of cotton in fields more or less distant from cotton fields of the previous 
year. Studies were conducted in 1921 on the influence that distance 
from source of infestation has upon the damage caused by the pink 
bollworm. Regular boll examinations were made throughout the 
season in four selected fields on the Tlahualilo property, located at 
different distances from 1920 cotton fields. Data on this experiment 
are given in Table 20. The four fields are hardly comparable in one 
group, as fields Nos. 1 and 2 were west of old cotton fields and Nos. 
3 and 4 were north. But field No. 1 is comparable with No. 2 and 
No. 3 with No. 4. Only a slight advantage is shown for the more 
distant fields. 
Table 20.— Pink bollworm infestation in 1921 fields located different distances from 
1920 fields 
[Worms per boll] 
Date 
Field 1 
(1,000 
meters) 1 
Field 2 
(2,750 
meters) 1 
Field 3 
(3,500 
meters) 1 
Field 4 
(6,250 
meters) 1 
June 23 ..- .. .... . . - 
2 0.06 
.01 
.008 
.038 
.47 
.44 
.54 
1.74 
2 0.09 
30 
.015 
.024 
0.075 
.037 
0.02 
July 8 
.002 
15 
.006 
.08 
.15 
.37 
.80 
.05 
.42 
.45 
.60 
1.07 
1.74 
.026 
22 . . - - 
.23 
29 . . 
.35 
.61 
ii :. 
1.12 
18 
1.69 
26 
2.84 
3.15 
Sept. 1. ._ -.- 
3.55 
3.32 
9 
6.02 
4.50 
15 
5.48 
4.34 
1.35 
1.01 1-35 
1.17 
1 Distance from 1920 fields. 
2 Not included in average. 
In Table 21 the results of nonpickable cotton counts made in 1921 
at 47 different points in unirrigated fields on the Tlahualilo property 
are presented with reference to the distance of these points from 1920 
cotton fields. 
Table 21. — Percentage of nonpickable cotton, 1921, in unirrigated fields, with ref- 
erence to distance from 1920 cotton fields 
Num- 
ber of 
points 
Distance from 1920 
fields (meters) 
Percentage of cotton 
nonpickable 
Average 
Range 
Average Range 
4,730 
250-1, 500 
2, 750-6, 250 
11.5 3 to 32 
10. 6 I 7 to 16 
Here again only a slight advantage is shown in favor of the more 
distant fields. Comparisons of individual fields in each group bear 
