exposed 7 days or to human volunteers exposed the equivalent of 2 working 
days. However, a definite effect was noted on the cholinesterase level of 
monkeys at the 2- and 10-gram dosage rates. Cholinesterase effects on the 
human volunteers were borderline and of questionable significance. Depression 
of the cholinesterase rate would have indicated a toxic effect. 
INTRODUCTION 
The problem of controlling the cigarette beetle in open (ventilated) and 
semi-closed tobacco warehouses which cannot be fumigated is particularly a- 
cute. A new insecticide has been developed which has proved unusually effec- 
tive against certain insects. This insecticide, Q, 0 dimethyl 2, 2-dichloro- 
vinyl dimethyl phosphate, is known as DDVP (2). 2/ Preliminary laboratory 
tests by the manufacturer (1) and by a cigarette manufacturer indicate that 
this material is effective against the cigarette beetle and does not impart 
an objectionable flavor or aroma to the tobacco. Studies on the mammalian 
toxicology of DDVP also have been reported (1). 
In preliminary tests, at an industrial laboratory, a solution containing 
100 parts per million of DDVP was sprayed directly on flue-cured tobacco, 
Cigarettes were made from this tobacco after 3 weeks, 6 weeks, and 3 months. 
Tests showed no change in the aroma or smoking quality of the tobacco. Cut 
cigarette tobacco was exposed for 6 months to an atmosphere saturated with 
DDVP vapor. Cigarettes made of this tobacco had normal smoking flavor. 
During the summer of 1956, 3 series of tests with DDVP were conducted, 
2 at Winston-Salem, N. Ce, and 1 at Charleston, S.C. The tests were de- 
signed to explore the usefulness of DDVP in controlling the cigarette beetle. 
They were carried out in commercial tobacco storage warehouses containing 
a total of 35 to 0 million dollars' worth of tobacco. The insecticide was 
applied by entomologists or by trained personnel under the supervision of 
entomologists. 
TECHNIQUES 
Warehouses 
Three types of warehouses were used: Type A, semiclosed; -type B, ven- 
tilated; and type C, closed. The type A warehouses were of corrugated iron 
construction, with wooden floors and composition roofs. These buildings were 
two stories high. Tests were made only in the second story, because insect 
infestation is usually higher there. Such storages had no windows or venti- 
lators, but were not tight enough for fumigation because of numerous small 
cracks where the sheets of corrugated metal overlapped. However, they were 
tight enough to prevent rapid movement of air through the building. 
37 Underlined figures in parenthesis refer to Literature Cited, pagel7. 
aeons 
