BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 9 
exposure to a heavy insect population. Uniform cloth was completely 
protected under similar conditions for 5 years. DDT-treated bags 
have protected raw wool stored in them for more than 18 months. 
Lindane, chlordane, and dieldrin are also giving long time protection 
in comparable tests. 
Method Developed for Forced Circulation of Fumigant in Loaded 
Grain Cars 
A method of providing forced circulation in the fumigation of 
loaded freight cars of shelled corn or grain sorghum was developed 
over the last two years in cooperative tests with the Western Plant 
Board. The first season's tests demonstrated that forced circulation 
was necessary to get effective distribution of the fumigant through 
the load mass. In the past year further studies developed a probe 
duct system that can be installed in loaded cars in a half hour or less. 
Air is drawn from the floor level through the perforated tips of the 
probes by a portable blower outside of the car, and returned to the 
space above the load to complete the cycle. When the fumigant is 
added to the air stream it is drawn down through the load of grain. 
Changes in State quarantine regulations to require this procedure 
were recommended to the Uniform Quarantine Committee of the 
Western Plant Board and were adopted by the Committee. 
Fortieth Ship Approved for Cold Treatment of Imported Fruit 
The fortieth ship was approved during the year to cold-treat fruit 
in accordance with the provisions of the fruit and vegetable import 
regulations. The requirements are that fruit originating in countries 
quarantined because of fruit flies be held below certain temperature 
levels in refrigerated compartments for designated periods while in 
transit. Continuous records of the fruit temperatures taken on auto- 
matic recorders during the voyage are the basis upon which the 
shipment is cleared upon arrival. From February to June 1953, in- 
coming shipments totaled 222,000 boxes of fruit from Argentina and 
190,000 boxes from South Africa. 
Electrical Apparatus Now Available To Determine Methyl Bromide 
Concentrations 
A unit for analyzing gas concentrations by thermal conductivity 
has been calibrated for methyl bromide and tested in the field. This 
unit is portable and will give readings as a sample of gas is drawn 
through it. It has great potentialities as a research tool as well as a 
practical instrument for commercial fumigators. The manufacturer 
of the unit is putting out special instructions for its use for methyl 
bromide determination. 
Approved Vacuum-Fumigation Facilities Rechecked 
All vacuum-fumigation facilities in Atlantic coast ports approved 
for the treatment of commodities regulated by quarantines have been 
examined. Gas distribution was checked for each fumigation cham- 
ber by analyzing gas samples withdrawn from representative locations 
