Evening star., 1935-11-03
Magazine Section
The Price of Pests
Continued from page fWo

PSyCu oii tilC ilOtIiSp uttl 81 kept tIleu
numbers down. Eventually some of
the European parasites were brought
in and used in the fight against tfie
rampant gypsies
But the most important outcome of
the Commissions inquiry was the
development of the practice of spray
ing. Its investigators experimental
with methods, devised and tried
various types of apparatus, pumps,
mixers, nozzles, and, above all, they
explored the chemists list of poisons.
All the familiar poisons we're tried.
and for one reason or another failed.
Most of them washed off during a
rain. But at last the Commission
found the object of its search in
compound known to chemists as ar
senate of lead. Though the stuff was
not expensive to make, it was so COM
mercially useless at that time that
only few ounces of it we're in ex-
istence. Today there are chemical
works that turn it out by the ton,
and many millions of pounds are con-
sumed every year. Not only the
gypsy-moth, but the worm of the
codling moth, the caterpillar and
score of other leaf-eating enemies are
overcome when they take lead arse
nate into their stomachs.
Late developments are insecticides
which kill merely by contact. and two
potent products of this kind have
recently been introduced - one dis
covered in the East Indies, the other
an introduction from Dalmatia and
Japan.
Years ago explorers came back from
the East Indies with stories of the
tuba fishing of Borneo. 1t seems that
the native fishermen dispense with
hooks and lines. Instead of digging
bait, they dig up the DOT of the tuba
plant. grind it and pound it into a
juicy pulp. and scatter this milky
mass into the river. Within a few min
utes stupefied fish rise to the surface,
and are scooped out Wholesale with a
hand net. Though the tuba juice kills
the fish. it does not harm the men who
eat the fish - and this selective
action of the poison amazed the
explorers.
Chemists analysed the tuba pulp
and isolated the poison in a white
crystalline substance which they
named "rotenone." When rotenone
was tried on various animals, it was
found that the poison killed cold
blooded creatures only, and was not
injurious to man or his warm -blooded
pets.
Closely paralleling rotenone in
many of its effects is ''pyrethrum."
This is substance extracted from the
dried flowers of "a small chrysan-
themum, a blossom which closely
resembles the white daisy of our
American fields. According to one
story. a woman in Dalmatia noticed
many dead flies surrounding dis
crded bouquet of pyrethrum bios
SONS. She was led to investigate, and
finally was convinced that the flowers
contained some chemical that was
deadly to insects. Whatever its origin
may be, considerable pyrethrum
industry developed in Dalmatia and in
Japan, and at present is in process of
developing in Africa.
Rotenone is both stomach poison
and contact poison. and might
prove the ideal substitute for lead
arsenate in spraying apples were it not
deteriorated by sunlight. Pyrethrum
kills solely by contact. and. like rote-
none, is injurious only to cold-blooded
creatures. Science has no experiment
to explain the action of rotenone, but
it has found that the effect of pyre-
thrum is paralysis.
Imports of both rotenone and pye-
thrum have increased during the
depression years, and we may expect
that with mounting demand there will