Evening star., 1953-02-11
Fly Swutter Is Still Best
OfWeopons in Bug War
Immunity to Single Poison
Aids Resistance to All Others
By Thomos R. Henry

BY Thomos R. Henry
High hopes Of winning mans war
against insects-which, 1t has been pre-
dicted. someday may destroy all higher
animals and inherit the earth-by
means Of poisons may prove quite futile.
The bugs everywhere are turning the
tables on the bug killers.
Describing Department of Agriculture
experiments with such diverse insects
as houseflieS and cockroacheS at o Ma.
tional Research Council conference, DR..
Frank H. Babers Of the Bureau Of En-
tomology said:
"Since resistance has been developed
by laboratory methods for all insecti-
cides for which the attempt has been
made, it seems probable that under the
proper exposure conditions in the field.
resistance may be expected to develop
to any inSecticide or mixture Of in
'secticides. It seems that chemicals no
longer can be relied upon for the main
line Of defense against insects for which
the residual type Of insecticides are
currently failing. Further research
should be aimed at determining the
physiological method by which resist
ance Is developed and at the same time
exploring all possible methods Of nom
chemical control"
Snowballing Immunity.
A disturbing fact, it was brought out
at the conference, is that once an in
sect race has developed relative i'm
munity to one kind Of poison they are
quicker to develop the same kind Of
immunity against all other kinds. Even
tually, races may develop immunity to
any poisonS.
The nature of the resistance mechan-
ism and how it develops, it was brought
cut at the conference, remains a good
deal of mystery. At first it was pre-
sumed to be merely manifestation Of
the survival of the f1ttest and the
elimination of the unfit-the ordinary
mechanism of evolution. In any ag-
gregation of houseflies, for example.
there will be some that will be less
susceptible to any particular poison
like DDT than the majority. The ma
jority will be killed. These few At in
dividuals will survive. Some Of them
will pass on their resistance to their
descendants. The rate Of multiplication
Of insects. Of course, is astronomical
and few pair in few years will pro-
duce an immune race. This, it was
stressed, undoubtedly is part Of the
story, but it is far from explaining the
whole phenomenon.
Another way to build up immunities
to some poisons is to start with ex-
tremely minute amounts and work up
to larger and larger doses. This is IL
lustrated by the relative immunity to
arsenic which can be acquired by some
humans. It might be another factor
in insect resistance. This acquired i'm.
munity, however, would not be con.
sidered hereditary.
Research Seeks Answer.
Neither explanation accounts for the
apparent hereditary resistance to all
poisons. Research, under National Re-
search Council direction, now is In
progress in several universities to de-
termine exactly what physiological
changes take place.
"At present." said DR.. Babers. I'VE
have dose Of what 10 years ago would
have been unheard-of chemicals. Ten
years ago we had lead arsenate and
pyrethrum. One could 60 out and get
some control lin the barn with pyre-
thrum, but there really was no adequate
control. Then along came DDT. It
lasted less than five years. Now q good
95 per cent of the effort is being di-
rected toward the search for new and
better chemicals. can't see It. In
five years all these good chemicals have
gone down the drain.
ely swatters are still good. We can't
kill our flies with DDT but we can still
kill them with fly swatters. We have to
catch them, Of course"
The impression left by the Depart
ment of Agriculture work, DR.. Babers
said, is that resistance develops rather
slowly to the first insecticide used.
After resistance to that poison 10
developed, immunity to future inSecti-
cides appears more and more rapidly.
This apparently is a manifestation Of
a hitherto unknown law Of nature
which physiologists still must deter
mine.