CRAZY-TOP DISORDER OF COTTON 
15 
, 
stems with aborted or shortened fruiting branches and the absence 
of bolls on the upper half of the plants. In part of the field previ- 
ously in alfalfa about 14 per cent of the plants showed abnormal 
top-growth characters, but all produced a good crop of bolls on the 
lower fruiting branches. 
In field 6 a narrow road divided the two differently treated areas, 
and the rows nearest the road were not included in the count, owing 
to the stunted condition of the plants. The most common abnor- 
malities to be found in the plants on the area following alfalfa were 
aborted terminal buds and divided stalks, while more than half of 
the plants in the area cropped continuously to cotton bore distinct 
crazy-top symptoms and were unproductive. The affected plants 
occurred both in groups and as scattered individuals throughout the 
entire length of the 600-foot rows. 
In order to determine if there were noticeable differences in the 
extent of the disorder in fields of cotton the first year after alfalfa 
and the second year after alfalfa, a count was made in representative 
sections of two adjoining fields of Pima cotton that had been planted 
in this sequence. The data obtained are given in Table 4. 
Table 4. — Comparison of prevalence of crazy-top disorder in Pima cotton plants in 
100-foot quadrats taken from areas planted to cotton in the first and second years 
folio wing alfalfa, respectively 
Row Xo. 
Cotton first Cotton second 
year following year following 
alfalfa alfalfa 
Crazy- 
top 
plants 
Xormal 
plants 
Crazy- 
top 
plants 
1 3 
2 2 
3 1 
4 6 I 
5 3 
6 6 
7 2 j 
8 4 
9 1 
10 2 
11 3 
12 2 
13 12 
14 2 
15 2 
16 
17 2 i 
X ormal 
plants 
Row Xo. 
30 I 
24 I 
29 
25 i 
21 
s 
55 
46 
48 I 
40 
7 
59 
33 
14 
50 
42 
14 
57 
25 
9 
63 
27 
13 
63 
S9 
16 
59 
43 
4 
42 
31 
9 
51 
28 
18 
33 
36 
11 
45 
33 
13 
53 
31 
23 
54 
Total 
Percentage 
Cotton first Cotton second 
year following year following 
alfalfa alfalfa 
C t r o7" i*°nn"l 
plants ! P lants 
75 
7.2 
. 35 
40 
29 
27 
26 
36 
30 
28 
35 
26 
21 
30 
30 
Crazy- 
top 
plants 
963 
20.1 
Xormal 
plants 
1,499 
It will be noted from Table 4 that only 7 per cent of the plants 
were affected in the area in cotton the first year after alfalfa, 
whereas approximately 20 per cent were affected in th^ area planted 
to cotton the second year after alfalfa. 
In order to determine the extent of the disorder in fields planted 
to cotton for the first time after several years in an uncultivated 
state, a count was made in a field of Acala cotton that had not been 
cropped since 1920, when a part of it was in Pima cotton. A corre- 
sponding area 75 feet away, in a field of Acala which had shown the 
disease for three years, was examined and the number of diseased 
and normal plants recorded. The results are shown in Table 5. 
