74 BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE [July-Sept. 
fruitfly quarantine, and of providing authorization for the low-temperature 
method of sterilization for the Mexican fruitfly for those in the citrus-fruit 
industry in Texas who desire to employ that method. Of the two heat-treat- 
ment methods authorized in the previous issue of the circular, only one is in 
current use, and authorization for this treatment as specified below is therefore 
continued with no change in method, other than the recommendation that in 
the use of wax or paraffine, applications of such material be made only after 
sterilization. ■ 
§ 301.64-4a Administrative instructions — Treatment of grapefruit and oranges 
for the Mexican fruitfly. Pursuant to the authority conferred upon the Chief 
of the Bureau of Entomology and Plant Quarantine by subsection (e) of 
§ 301.64-4, Chapter III, Title 7, Code of Federal Regulations [regulation 4 of 
the regulations (third revision) supplemental to Notice of Quarantine No. 64, 
the Mexican fruitfly quarantine] , the methods of sterilization specified below are 
hereby authorized, effective September 25, 1941, as a condition of the issuance 
of permits for interstate movement of grapefruit and oranges. 
• (a) Vapor-heat method. — Heating the fruit for a period of not less than 14 
hours during which time the fruit shall be raised to a temperature of 110° F. 
at the approximate center of the fruit and shall be maintained at or above that 
temperature for the last 6 hours of such treatment. 
While no specifications as to the exact methods and equipment for obtaining 
these conditions are prescribed, the air within the room shall be maintained at 
the temperature and under the humidity conditions required by the supervising 
inspector. Available information clearly indicates that by the application of 
dry heat the required temperatures cannot be reached without injury to the 
fruit. To prevent such injury it is necessary to maintain a very high humidity 
throughout the period of treatment. In the tests where successful performance 
was obtained, live steam as the source of heat was applied in such a way as to 
secure as nearly as possible a uniform distribution of steam-heated air so 
directed as not to discharge directly on the fruit. The air temperature ranged 
from 110° to 112° F. and the air was very moist. The fruit was held in field 
boxes stacked four boxes high and without special means of separating the 
boxes in each stack. The experiments indicate that the fruit should be steri- 
lized after coloring, if this is necessary, and before packing for shipment, and 
then cooled down to a temperature around 45° F. as soon as possible after 
sterilizing. Wax or paraffine, either dry or in solution, should not be applied 
to this fruit before sterilization. 
(b) Low-temperature method. — (1) Cooling until the approximate center of 
the fruit reaches a temperature of 33° F. and holding the fruit at or below that 
temperature for a period of 18 days. 
(2) Cooling until the approximate center of the fruit reaches a temperature 
of 34° F. and holding the fruit at or below that temperature for a period of 20 
days. 
(3) Cooling until the approximate center of the fruit reaches a temperature 
of 35° F. and holding the fruit at or below that temperature for a period of 
22 days. 
Such treatments as specified in (a) and (b) above are authorized in steriliza- 
tion or refrigeration plants in the regulated area which are approved by the 
Bureau of Entomology and Plant Quarantine. The Bureau will approve only 
those plants which are adequately equipped to handle and sterilize the fruit. 
Such sterilization will be done under the supervision of inspectors of the 
Bureau. These inspectors should at all times be given access to fruit while 
in process of sterilization. 
While the results of the experiments so far conducted have been successful, 
it should be emphasized that inexactness and carelessness in operation may 
result in injury to fruit. In authorizing the movement of fruit sterilized in 
accordance with the above requirements, it is understood that the Department 
does not accept responsibility for fruit injury. 
Done at Washington, D. C, this 19th day of September 1941. 
P. N. Annand, 
Chief. 
[Filed with the Division of the Federal Register September 25, 1941, 11 : 03 a. m. ; 
6 F. R. 4897.] 
