er umeoesleWen ON BULL ETON 9 
PESTICIDES AND ECOLOGY 
By Mrs. Arthur M. Jens, Jr. 
To many thinking people, it is becoming increasingly obvious that pest control 
is an ecological problem of pest population management. Highly toxic, per- 
sistent, non-selective chemical pesticides are a phenomenon of our century. 
They have been used copiously in spite of evident side effects (which are 
often major effects), and without full knowledge of other possible hazards. 
Although pesticides have been applied to a relatively small part of our land 
area, their residues are being found far away from the points of application. 
Persistent poisons have become a part of our environment, unfortunately an 
unmonitored part. 
Monoculture, with acre upon acre of the same crop, furthers simplification of 
the ecosystem and invites pests. (Courtesy Illinois Natural History Survey). 
While there is encouraging evidence of planned reduction in the amounts 
and persistence of the poisons used in many programs, there are still hazards. 
“It is often asserted—quite accurately—that rates of application are too low 
to cause direct wildlife mortality,’’ writes Dr. Thomas G. Scott, Oregon State 
University. “But valuable wildlife may be forced to contend with a reduc- 
tion of primary food sources. It has also been shown that chemical residues 
can be concentrated through food chains. Insects and other food organisms 
may develop resistance to a chemical or naturally tolerate high levels. Thus, 
birds, mammals, and fish which feed upon these organ’sms receive an ex- 
posure to pesticides at higher concentrations than would otherwise be avail- 
able in their environment. Contaminated food chains hold the added danger 
of exposure to more than one kind of pesticide, and combinations may be 
more toxic than the sum of the toxic potentials of each component. As a 
consequence, persistent pesticides applied at low levels may produce delayed 
effects on many forms of wildlife.’ (9) 
