More About DDT
Nature Bulletin No. 37 October 20, 1945
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Supt. of Conservation
MORE ABORT DDT
Since issuing the previous bulletin on DDT, the Forest Preserve District
has received numerous reports on this subject from several government
agencies which are conducting experiments with DDT, and from
individual scientists also studying its effects upon other insects, birds,
mammals and plants.
It appears that mosquitoes and flies are more sensitive than most other
insects but that no field tests have been carried out which did not also
result in killing other kinds, due to excessive local dosages, This is
Many of our fruits, vegetables and flowers are cross-pollinated by
insects, and were such insects destroyed these crops would be greatly
reduced with disastrous results. Further, insects and their allies, such as
the countless mites which live in the litter of decaying leaves and other
vegetable matter carpeting a forest floor, play a vital role in the
production of a mature soil and the health of the forest.
All experiments on spraying forest areas with DDT which have
included careful biological studies, confirm the opinion that such
operations are potentially dangerous to most insects and their allies as
well as to mammals, birds, reptiles, fish, amphibians and even some
plants. Sometimes it kills birds and sometimes not. It has not been
proven whether the birds die from eating the insects or from direct
effects. The dosage, denseness of foliage, latitude, temperature, etc.
seem to be the important factors.
In water its effects are deadly to fish, mussels, aquatic insects and even
some plants unless the dosage is very light.
The consensus of opinion is that DDT should not be used other than in
buildings, on dumps, etc., unless under the direction of competent
scientists, and that it should not be used at all in the forest preserves
until more is known about it.
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Update: June 2012