STUDIES OF THE PINK BOLLWOKM IN MEXICO 
51 
ately before and one immediately after the sample for examination 
was taken, and determining the temperature of the seed in these 
buckets. The difference between the two temperatures in most of the 
tests can likewise be ascribed to differences in feeding and to varia- 
tions in steam pressure. The temperature readings should more or 
less represent the minimum and maximum for each sample examined. 
Next, a series of tests was conducted in which the period of ex- 
posure was decreased by lowering the discharge end of the machine. 
Otherwise the method of operation was identical with that in the 
first set of tests. The results are given in Table 43. 
Table 43. — Tests conducted with a dry-heat disinfecting machine for destruction of 
• the pink bollworm in cotton seed 
[Time of exposure ranging from 1 minute to V-A minutes] 
Test 
No. 
Steam 
pressure 
Time of 
exposure 
Number 
of larvae 
in test 
Temperature 
of seed on dis- 
charge 
Mortality 
Pounds 
Minutes 
Degrees F. 
Per cent 
256 
33-36 
1X-2M 
0) 
130 -132.5 
0) 
255 
37 
VA-VM. 
17 
139 -138 
70.6 
257 
39-39 
V/t-Wt 
20 
141 -140.5 
100 
252 
26-26 
iX-®i 
19 
141. 5-144 
100 
258 
47-45 
1M-2M 
26 
146. 5-143 
96.1 
254 
40-38 
l -2V 2 
14 
148 -143.5 
100 
259 
49-48 
1M-2M 
36 
148 -145 
100 
253 
35-37 
i -m 
32 
147 -151 
100 
1 No examination. 
The result shown in these two tables tends to substantiate the con- 
clusion, drawn by McDonald and Scholl, 17 that seed exposed to dry 
heat so that it attains a temperature of 145° F. in a period of 3J^> 
minutes is effectively disinfected. 18 That 100 per cent mortality 
is not obtained by snorter exposures, even though a temperature of 
145° is recorded, is no doubt due to the fact that the interior of 
individual seeds, when immediately cooled, does not attain the 
temperature recorded by the seed if bulked for a short time after 
exposure. 
LIVE-STEAM PROCESS 
The type of machine just discussed, although found to be effective, 
heats the seed rather slowly. Also, a machine of greater capacity 
was desired to meet the needs of large gins 19 where the installation 
of machines of the first type with proper capacity would be an 
expensive item. To meet these requirements a machine was de- 
veloped in which the seed is heated by injecting live steam into the 
seed mass. Much more rapid heating is brought about in this 
manner. A machine of this type was sent to Tlahualilo and tested 
by J. C. Woodward. 
The machine consisted of three inclosed 10-inch screw conveyors. 
The seed is fed into one end of the top conveyor and is discharged 
at the opposite end of the bottom conveyor. Immediately under- 
neath each conveyor is a partly inclosed steam pipe. In the upper 
side of this pipe are a number of small perforations through which 
" R. E. McDonald, and G. J. Scholl. Op. cit. 
18 In experiment No. 258, a temperature of 145° F. was reached, but the mortality was less than 100 per 
cent. It will be noted, however, that the exposure was only 2M mihutes. 
18 Later experiments have shown that the capacity of the machine can be increased indefinitely by in- 
creasing its size. 
