12 
BULLETIN 1484, U. 3. DEPARTMENT OF AGRICULTURE 
RELATION OF CROP SEQUENCE TO PREVALENCE AND SEVERITY 
OF THE DISORDER 
In comparing the prevalence of the crazy-top disorder in areas 
cropped to cotton for several years with adjoining areas in which 
cotton followed a crop of alfalfa, it was noted that there were marked 
differences in the extent of the disease and the character of the mal- 
formations. In eight cases where the writers were able to find both 
conditions within the same field, the disease was found in every 
instance to be more prevalent and to have more pronounced symp- 
toms in the areas cropped continuously to cotton than in the areas 
following alfalfa. In six of these fields, three of Pima and three of 
upland cotton, conditions were favorable for obtaining statistical 
material from a study of the plants at the immediate junction of the 
two areas. In four of the fields a squa.ce area 100 by 100 feet was 
selected at random and staked out on one side within a few feet of 
the dividing line, and a similar area was staked out on the other side 
of the line. In the other two fields, where the rows of the differently 
treated cotton plants lay parallel, the plats measured were also 10,000 
square feet in area but were oblong rectangular instead of square. 
A count was made of the distorted and of the normal plants in these 
areas and the results tabulated. The data obtained from three fields 
of Pima cotton where both conditions existed are given in Table 2. 
Table 2. — Number of normal and crazy-toy Pima cotton plants in contiguous 100- 
foot quadrats from areas cropped to cotton continuously and adjoining areas 
following alfalfa 
Field No. 1 
Field No. 2 
Field No. 3 
Cotton con- Following 
Cotton con- Following 
Cotton con- 
Following 
Row No. 
tinuously j alfalfa 
tinuously | alfalfa 
tinuously 
alfalfa 
Crazy- 
Nor- Crazy - 
Nor- 
Crazy- 
! 
Nor- Crazv- 
Nor- 
Crazy-! Nor- 
1 
Crazy-j Nor- 
top 
mal top 
mal 
top 
mal j top 
mal 
top mal 
top 1 mal 
plants 
plants 
plants 
plants 
plants 
plants j plants 
plants 
plants 
plants plants 
plants 
1. 
32 
24 
26 
19 
19 
10 
9 


37 
44 
44 
38 
32 
16 
37 
42 
58 
1 
g 
3 
28 
30 
37 
11 
13 
10 
17 
17 
8 
8 
4 
5 
28 
2. 
19 
3 
29 
4. 
30 
45 
49 
32 
40 
10 
6 
7 
12 





39 
39 
41 
35 
36 
22 
23 
24 
2 
15 
54 
2 
48 
29 
39 
34 
46 
16 
35 
51 
47 
51 
11 
10 
4 
12 
7 
3 
14 
57 i 6 
49 3 
53 1 
50 6 
21 
6. 
12 ; 13 
7. 
12 
8. 
26 
20 
9. 
37 
29 
32 
24 
28 
35 
41 
10 

47 
43 
41 
41 
40 
40 
47 
28 
28 
34 
15 
24 
22 
24 
51 
34 
22 
53 
48 
55 
41 
1 
4 
4 
2 
3 
3 
5 
43 
45 
37 
54 
35 
50 
39 
42 
29 
36 
29 
10 
13 
9 
IS 
10 
14 
13 
25 
10.. 
10 ; 
17 
24 
18 
11 
31 
12.. 
19 j 25 
13 
18 
8 
10 



40 16 
16 10 
29 10 
12 30 
14 
15 26 
15 
15 i 33 
16 
28 
32 
18 
14 
11 
12 
13 
31 
43 
44 
2 
1 



41 
62 
54 
49 
64 
17 
14 
22 
22 
19 
39 
33 
42 
26 
26 
3 

1 
2 
35 
35 
30 
36 
32 
24 6 
14 18 
20 20 
29 16 
11 12 
12 ' 23 
17 
12 
18 
17 
21 
17 
31 
19 
26 
20 
43 
21 
14 
40 

55 
27 
36 
51 
30 
18 
9 
34 
22.. 
12 
47 

52 
15 
36 
37 
13 
4 
11 
40 
23 
10 
42 

81 
33 
27 
53 
35 
4 
10 
41 
24- 
13 
44 

81 
32 
24 
45 
49 
7 
17 
41 
25 
9 
42 

51 
41 
40 
2 
47 
26 
4 
15 33 
26 
9 
44 

51 
25 
53 

59 
43 
2 
11 32 
27 
9 
41 

65 
10 
46 
4 
32 
26 

5 24 
28 
10 
46 

70 
21 
53 
2 
41 
46 
12 
9 38 
Total. 
693 
674 
3 
1,390 
645 
1.185 
69 
1,127 
821 
300 
341 800 
Percentage. .. 
50.7 
0.2 
35.2 
5.8 
73.2 
29.9 
