Distribution of aerosols, as indicated by the deposits on the glass 
slides, was poor. The heaviest deposit on the slides was nearest the point 
of introduction, and no deposit occurred in the most distant areas, It was 
visually observed that the aerosol failed to reach the far ends of the ware- 
houses. 
There was no indication of organophosphorus poisoning of any of the ex- 
posed rats. No lowering of the cholinesterase level in the blood of the rats 
was found 3 days after the end of their exposure in the warehouses. 
TESTS WITH DDVP APPLIED AS AN AEROSOL 
Procedure 
In this series of tests the DDVP was applied as an aerosol in three type 
A (semiclosed) warehouses. A constant amount of solution of 53 ml. per 1,000 
cubic feet of total warehouse space was applied in each warehouse, The con- 
centration of DDVP was varied to give dosage rates of 1, 2.1, and 4.25 grams 
per 1,000 cubic feet. The warehouse temperatures averaged about 85°F, 
Sets of 30 cages of beetles were placed on top of the tobacco hogsheads 
at various levels and locations throughout each warehouse. Each cage con- 
tained 25 adult beetles and a l-inch section of midrib bearing eggs. Cages 
were placed 16 hours after aerosols were applied. Lots of cages were removed 
after exposure periods of , 12, 18, and 2) hours. An additional set of 6 
cages was placed in each warehouse 7 days after the application, and exposed 
for 2) hours. 
Before the application, test spikes were inserted in selected hogsheads 
so that samples of adults were placed 1, 3, and 5 inches deep, and samples of 
larvae 1, 3, 5, 7, and 9 inches deep. One spike of each stage was removed 
after exposures of 2), 8, and 72 hours. 
Results 
The insect mortality results are given in table 2. All adult beetles 
were killed when exposed in the free air spaces for ) hours or more, 16 hours 
after application, at dosages of 1 gram per 1,000 cubic feet or above. 
Adults exposed for 2); hours, 1 week (168 hours) after application, at a dos- 
age rate of 1 gram, showed 13 percent mortality; at a rate of 2.1 grams, 65 
percent mortality; and at a rate of ).25 grams, 83 percent mortality. How- 
ever, eggs hatched normally when exposed in the free air space to all appli- 
cation rates tried and with exposures up to 2); hours. There was no signif- 
icant mortality of either adults or larvae at any depth in the tobacco 
hogsheads. 
