﻿STUDIES. OF THE PINK BOLLWOEM IN MEXICO 55 



pressure and feeding, however, it was difficult to obtain a certain 

 desired temperature in any one test, and the temperatures obtained 

 in any series were usually very irregular. To this same irregularity 

 in steam pressure and feeding can be ascribed the wide variations in 

 temperature indicated in some of the individual samples. 



In the tests recorded in series 1, 2, 3, and 4 steam was admitted 

 into the upper two conveyors of the machine only. The results in 

 these four series show the maximum temperatures that failed to give 

 100 per cent mortality for the respective periods of exposure to be as 

 follows : 



Series 1, 1 minute, 5 seconds, 1423^° F. 

 Series 2, 55 seconds, 143° F. to 142° F. 

 Series 3, 49 seconds, 152° F. to 148° F. 

 Series 4, 47 seconds, 144° F. to 145° F. 



In series 5 steam was admitted into the two lower conveyors only 

 and the seed required 1 minute and 8 seconds to pass through the 

 machine. This would of course be equivalent to a machine with two 

 conveyors only and an exposure of about 46 seconds. In series 6, 7, 

 and 8 steam was admitted into the top conveyor only. The results 

 in these series show the maximum temperatures that failed to give 

 100 per cent to be as follows: 



Series 5, 1 minute, 8 seconds (46 sec), 160° F. 

 Series 6, 1 minute, 8 seconds (all 100 per cent). 

 Series 7, 55 seconds, 140° F. to 138° F. 

 Series 8, 47 seconds, 143° F. to 145° F. 



These eight series throw considerable light upon the action of a 

 machine of this type. In series 1 and series 5 the time of exposure is 

 the same, or practically the same, and in each steam is admitted into 

 two sections of conveyor. Under equal pressure this .should heat the 

 seed equally. Yet series 5 shows a failure at 160° F., and in series 1 

 142 3/^° is the maximum that did not give 100 per cent mortality, 

 and it is a doubtful record. Other tests in series 5 compare with 

 those in series 1 in a similar way. This brings out the point already 

 mentioned, that the record obtained immediately after exposure does 

 not show the temperature attained by the inside of individual seeds. 



From this it may be concluded that, in the test in series 5, enough 

 steam had been injected into the seed mass to raise the seed to a 

 temperature sufficient to kill the pink bollworm, were it bulked 

 long enough to allow even heating throughout the mass by absorp- 

 tion. This at the same time explains the better results obtained 

 when steam was admitted into the upper conveyors only, giving 

 opportunity for absorption of heat while the seed was passing 

 through the lower dry conveyors. 



The results obtained in these tests warrant the conclusion that a 

 machine of this type will be successful if operated so that the seed 

 is discharged at a temperature of not less than 145° F. after an 

 exposure of at least one minute, during the first half of which it is 

 subjected to steam, the remaining time being allowed for penetra- 

 tion of the heat to the larva inside the seed. The temperature 

 record should be obtained at a point near the discharge end of the 

 machine. 



EFFECT OF LIVE-STEAM TREATMENT ON aEHMINATION 



A number of germination tests with samples taken from the series 

 of tests just discussed were madf;. The results are given in Table 45. 



