Table 6.-=Content of DDVP in air in tobacco warehouses at various times 
after treatment with the insecticide at different dosages 
Tntervalclatter DDVP content (micrograms per liter) at-- - 
treatment ~ Ll gram per: © grams per: 10 grams per 
: 1,000 ens fos: 1,000 CUls. ttie es 1,000 Culenericrs 
eo 28 8 
Dea-NOuUrs <s- 5 Me Mle Heer Ozta, moe DS Oise aunt -- 
PMGNOUNS! 4 -eldeme eons APL ee Alps a0) 0.9 
NGiOUnS o tayek vets fe ue (Lass aii ah 
BGaVSe se jelceneimelne’ ts =< == -- 
1 Gayse. siteceowe. cue <.0L, <.oh LOG. Ol eal 
distribution of DDVP aerosols in the exploratory series, the aerosols were 
not observable in some parts of each warehouse, and only a small part of each 
warehouse showed deposits on the slides. Yet complete kills of test insects 
occurred at all points in the air spaces in the buildings, Furthermore, in 
type A (semiclosed) warehouses, the vapors apparently permeated the entire 
air space and continued to kill all beetles for 3 days, This reaction was 
further demonstrated where the treatment with DDVP consisted of sprinkling 
a solution of the material on the floor of the aisle. In all test warehouses, 
the vapors quickly permeated the air space and killed insects 100 feet from 
the points of application. It is noteworthy that this action was not found 
to occur in ventilated buildings. Where there was air movement through the 
warehouse, apparently it was impossible to build up lethal concentration of 
Vap OF e 
This vapor movement is a matter of considerable importance. One of the 
greatest limitations in the use of aerosols and space sprays to control the 
cigarette beetle has been the difficulty of obtaining adequate distribution. 
Tobacco warehouses are usually very large and so designed and so filled with 
tobacco that satisfactory distribution of spray is frequently unobtainable, 
The use of DDVP might solve this problem. 
Another useful property of this insecticide is its short residual action. 
A deposit of DDVP in a tobacco warehouse will continue to liberate vapors for 
several days. However, it is sufficiently volatile that, at practical dos- 
ages, all or most of the material vanishes in about 2 weeks, as shown by the 
air concentration values, This gives some prolongation of insecticidal action, 
but seems to eliminate all fears of permanent insecticidal residues contami- 
nating the tobacco. 
UT 
