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individuals have natural immunity. In ‘this instance, such adapted indi- 
viduals survive after D.D.T. application and produce resistant progeny. 
Larger doses may be required to kill individuals of this new generation. In 
an ecological community, reproductive success of the survivors would be 
greatly increased by the removal of some biological controls (e.g., pre- 
daceous insects, birds, etc.). 
When we consider all factors together and see how little is known about 
insecticidal control measures in relation to development, habits, and func- 
tion of the target animals, we realize that we are using ecological communi- 
ties as extensive experimental areas. The resulting effects on wildlife, and 
the potential threat to humans, definitely makes such practices unwar- 
ranted. The usual experimental work carried on in chemical laboratories 
does not indicate the long-range effects of pesticides, especially upon non- 
target organisms. 
With a sanitation program we can possibly reduce the population of bark 
beetles to a level controllable by biological elements (birds, other insects, 
etc.) which are now also being destroyed by the pesticides. With Dutch elm 
disease we have an opportunity which is seldom offered in other diseases 
transmitted by insects: we can locate and remove most of the potential 
breeding sites. If we are not willing to pursue such an extensive program 
we should not, in the light of the evidence available, pursue a program in- 
cluding insecticides because thereby we imperil other organisms that are 
equally valuable to man. We must consider all of the ecological inter- 
relationships interrupted by the removal of birds, beneficial insects, mam- 
mals, and other organisms. Through entomological studies it should be pos- 
sible to find control measures that could be directed to a particular species. 
Perhaps application of such chemicals would be more expensive, but econo- 
my should not govern such extensive programs. Insecticides have played an 
important role in agricultural production and in many aspects of public 
health. However, it is only sensible to consider the overall situation before 
proceeding with a program involving an entire community and not just a 
tilled field. 
In view of the evidence available it appears that the best control measure 
for Dutch elm disease, at the present time, is complete sanitation. If such a 
program is not in effect in your area, the following procedures set up by 
the Illinois Natural History Survey are recommended: 
An Outline of Organization for Control of Dutch E!m Disease 
1. Call the problem of Dutch elm disease to the attention of local municipal 
officials and civic organizations. 
2. Arrange through civic organizations to hold a public meeting to acquaint 
the local public with the nature of the disease and the possibilities for 
its control. 
3. Form an elm tree committee to work for a control program, including 
representatives from civic and municipal organizations. 
4. Obtain the services of a professional forester or aborist to evaluate, 
design, and supervise a control program. Such a consultant should have 
no commercial interest in the project. 
5. Survey the elm population in the community to estimate the value of 
the trees to be protected and the costs of suitable control. 
6. Review all available information on control of the disease in order to 
design a program suitable for your community. 
