Dec. i, 1923 
Habits of the Cotton Rootrot Fungus 
409 
EFFECT OF SOIL CONDITIONS ON THE PRODUCTION OF FRUITING 
BODIES 
The production of the fruiting bodies in rootrot spots seems to be 
somewhat dependent on the soil conditions. In the Salt River Valley 
no fruiting bodies were observed in infected cotton fields of a sandy 
nature, no matter how favorable the weather conditions. In 1918, 
however, fruiting bodies were observed in two instances in infected 
alfalfa fields in soils of a sandy character. Although found in abundance 
during the seasons of 1921 and 1922 in the alfalfa fields near Sacaton, 
where the soils are composed largely of fine sand and silt, fruiting bodies 
were never seen in infected cotton fields of that region, although diligent 
search was made during the fruiting periods. The promptness with 
which the surface of sandy soils dries out after rains, when not covered 
by some dense crop such as alfalfa, probably explains the absence of the 
conidial mats in sandy areas. With the exception of one field the sandy 
areas at the time surveyed did not appear to be seriously infected. Soil 
samples taken from one of the spots in this badly infected field gave a 
moisture equivalent of only 3.8, while the soils typical of the largest 
and most severely infected areas in the Salt River Valley gave a moisture 
equivalent of 20 to 24. In Table I is given a list of infected fields under 
the writer’s observation in 1918, with their soil type and estimates as to 
the number of fruiting bodies observed during the summer. The fields 
varied in area from 2 to 16 hectares, and the infected portions were 
roughly estimated. It will be observed that there appears to be a fairly 
close correlation between the presence of the fruiting bodies and heavy, 
finely divided soils. 
Table I.— Location of fields with crops and areas infected with rootrot in iqi 8, and the 
type of soil and estimated number of fruiting bodies observed 
Field No. 
Crop infected. 
I . 
Alfalfa. 
2 . 
.do. 
3 . 
.do. 
4 . 
.do. 
.do. 
6 . 
.do. 
7. 
Cotton. .. 
8. 
Alfalfa. 
.do. 
10. 
Cotton. 
II. 
.do. 
12. 
.do. 
.do. 
14 . 
.do. 
IC . 
.do. 
16 . 
.do. 
17 . 
.do. 
18. .. 
.do. 
10 . 
Alfalfa. 
20 . 
Cotton. 
21 . 
.do. 
22 . 
.do. 
.do. 
24 . 
.do. 
4 
Estimated 
area of 
field 
infected. 
Estimated 
fruiting 
bodies per 
100 square 
meters. 
Ares a 
202.3 
5 
44 - 5 
80.8 
12. 1 
202. 3 
202. 3 
3 
161. 8 
18 
20. 2 
80. 9 
2 3 
121. 4 
6 
202. 3 
80. 9 
5 
40 - 5 
13 
80. 9 
7 
121. 4 
11 
16. 2 
3 
202.3 
21 
20. 2 
60. 6 
80. 9 
40. 5 
12. 1 
5 
20. 2 
16 
40. 5 
3 
Kind of soil. 
Silt loam. 
Sand. 
Do. 
Do. 
Sandy loam. 
Clay loam. 
Clay loam—stony subsoil. 
Clay loam. 
Do. 
Adobe—calcareous subsoil. 
Clay loam. 
Adobe. 
Clay loam. 
Adobe. 
Clay loam. 
Sandy loam. 
Sandy loam—stony subsoil. 
Sand (coarse). 
Clay. 
Clay loam. 
Do. 
Adobe. 
Adobe—stony subsoil. 
Adobe—loamy subsoil. 
a An are is ioo square meters. 
