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 
serious.

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.