Evening star., 1952-03-24
New Drug Makes Plants
Deadly to Harmful Bugs
y. 5. Tests Two Insecticides
Which Won't Hurt Some Life
By Thomas r. Henry

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Two new Insecticides, products of Gers
man war science. which make plants
deadly to harmful bugs without injuring
beneficial ones, now are being subjected
to intensive tests ana are awaiting De-
partment Of Agriculture approval.
Both are Of the type Of chemicals
know as organic phosphates They are
taken up Ii the sap stream Of q plant,
making It toxic TO chewing and sucking
insects but harmless on contact with
others which may be beneficial.
Their potency Is such that an ap-
plication Of rs little ~ . quarter pound
an acre may be suficient. according to
report issued by Arthur d. Little Inc.
The first oficial approval may be lin
tied to ornamental plants, until the ef-
fects Of the poisons on higher animals
can be thoroughly determined.
Both materials. according to the re-
port. can be applied by spraying on the
foliage or through the roots by irrigation
or ground soaking. The insecticide moves
from the roots and stems to the leaves
more efiiciently than from leaf to leaf.
so that more material Is needed for leaf
spraying.
Toxicity Period Varies.
Eventually. according to the report,
chemical action within the plant renders
the poison ineffective. The period Of
toxicity varies with the insecticide and
the stage Of plant growth at the time
of application. On young, actively grow
ing plants the effective period for one Of
them. now available In experimental
quantities, may be from four TO six weeks.
In older plants 1t may be considerably
longer. This has the jaw-cracking name.
octamethyl pyrophosph The
other chemical dissipates faster initially
but retains q minimum insect killing
efficacy for g longer period.
Because Of the danger Of poisoning
human beings, Department Of Agricul-
ture regulations probably will demand
period Of at least six weeks between
the last spraying and harvesting.
Current use with commercial crops Is
limited to experimentation.
In spite Of q, lot Of new insecticides
developed within the past few years,
according to the bulletin, the bugs are
gaining ground. The loss last year was
estimated at about "a billion and It is
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to recent mild winters which allow the
pests to live to another spring. Also.
it Is claimed. conventional insecticides
often permit the pest population to
bounce back to new highs after each
treatment. Some Of the newer insecti-
cides kill not only harmful insects, but
also other insects which prey upon
them.
When large proportion Of best pest
and beneficial insects is killed. the re-
naming beneficials may migrate to
seek another food source. The field is
left clear for the surviving pests and
their relatives to multiply faster than
ever.
Il Natures Balance Necessary.
Another drawback in recent years
mas been the development Of insect
strains resistant to poisons. 81
Many experts believe" says the bul-
letin, .tthat attempts to achieve 100 per
cent destruction are futile and prohibi-
lively expensive and that, by seeking TO
restore the balance OF nature, losses to
insects can beskept tAt a reasonable level
at reasonable cost. Y il9as q
sIn areas where methods Of agricul-
tlire have not interfered with the normal
predator-prey relationship. the problem
Of insect pests Is less serious. But when
large areas are devoted to single crop,
the rich food supply calls forth an un-
usually large pest population. Deliberate
steps must be taken to hasten the ap-
pearance of natural enemies. BY using
selective insecticides. the pest popula-
ton is kept down and control may be
aided by beneficial insects"
The new materials. II says, appear
especially good from this point OF view.
One Of them, for example, kills high
percentage Of aphids but has little effect
on ladybugs which feed on them.
One application kept q crop free OF
cabbage aphids all summer. Recent ex.
periments with the other show excel
lent control Of sucking insects. Neither
appears to have any bad effect ON birds
or bees.