DDT AND OTHER NEW INSECTICIDES 
During the past growing season we used DDT spray, experimentally, on dahlias 
under the supervision of Drs. L. J. Alexander and R. B. Neiswander of the Ohio 
Experiment Station and in conjunction with a fact finding survey by the E. |. duPont 
De Nemours & Co., Inc. of Wilmington, Del. Results and observations of our program 
have been forwarded to the DuPont Co., at their request, to be used as a part of the 
basis for their recommendations to appear on their product. 
The material used here was a DuPont product called DEENATE 25-W containing 
25% wettable DDT. This is a powder (talc) into which DDT (Dichloro-Diphenyl- 
Trichloroethene) has been incorporated and which readily mixes with water to form a 
suspension (not a solution). DDT in solution (in oils), as sold for household pest 
extermination as a liquid, is quite toxic, or injurious, to plants and more dangerous 
to the user. In the extremely fine microscopic particles, as in the powders prepared 
for plant application which form suspensions in water, it does not injure plants at the 
recommended concentrations and does not seem to effect the skin and can easily be 
washed off the hands and face. 
Several concentrations of the material were tested here with check rows and in 
comparison with other materials. In a very short time it was evident that DDT was 
far superior. Comparison sprays and check rows were discontinued in favor of DDT. 
A .75°%, {three quarters of one per cent) spray was used over all during the latter part 
of the season with remarkable control of the insects prevalent, with the exception 
of red spider and aphids. However, it is likely that where corn borers and Jap 
Beetles are serious a 1% spray would be better. Our present recommendations for 
each insect appear under the name of the insect on pages 39 to 41. We suggest 
that the manufacturer's recommendations for control of the particular insect, or insects, 
be used instead of those we recommend as their recommendations will be based on 
many other tests besides ours. 
DDT is compatable with: most other insecticides, except those containing lime, 
and can safely be combined with them for a ''one application" spray. 
Former insecticides killed by contact, paralysis, or as stomach poisons. A few 
combined two of these actions. DDT combines all three, hence one reason for it's 
greater effectiveness. Also it is toxic for a longer period than most other insecticides. 
It is not as rapid in it's effect as some of the others but is definitely more certain. It 
is not necessary that the insect be present at the time of application, as is the case 
with. most insecticides. An insect walking across sprayed foliage long after application 
is doomed to almost certain death. Spraying once every two weeks is usually sufficient 
for good control, although we preferred an application at ten day intervals. Rain 
shortly after applying does not reduce it's effectiveness noticeably. Thoroughness of 
application is less important, although preferable, so that the need for high powered 
sprayers is less important than for many other insecticides. Spraying may be done at 
any time of the day or evening and it doesn't matter whether it is warm or cool at 
the time. Cost of the material is low. 
To prepare a 1% spray would require four pounds of a 25% powder to 100 
gallons of water. If a 50% powder is used only two pounds of it are required. In 
other words, it requires one pound of actual DDT to 100 gallons for a 1% spray. If your 
powder contains 25% DDT (or a one fourth of each pound) it will require four 
pounds to equal one full pound of actual DDT. 
Experiments have shown DDT to be nearly as effective on most insects when 
used as a dust, in which case a 3% dust seems to be about the equivalent of a 1% 
spray. A 3% dust can be prepared by using !2 pounds of the 25% powder in 100 
pounds of finished dust, which would be 12 pcunds of the powder to 88 pounds of 
talc. DDT should be mixed with talc or sulphur, not lime. If dust is used it is likely 
that it should be applied oftener than the spray, possibly at weekly intervals. 
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