Evening star., 1933-07-23

IN our struggle Tor an a0equaCe 1OOQ supply.
We can't go into the fields with squirt guns
and insecticides to destroy our food crop enc
mics. So we have had to evolve newer and
more wholesale method of destruction. This
new method is based on knowledge Of their
life cycles-intimate studies Of their habits.
associations and the effect Of weather condl-
tofls on their populations
"Viewed from this standpoint the man in
the field with his tall poles and cone bags on
top ceases to be an individual and becomes
Q giant symbol of science defending the food
frontiers of the world against insect destroy
ers"
During certain periods Of their lives insects
present greater vunerability to death than at
other periods. BY determining just what these
periods are science is able to concentrate on
the enemy hosts at this particular time and
Wreak destruction. These periods OF vulnera-
bility are based on the development and
growth Of the insect. This life cycle Is marked
by three or more divisions. With some insects
the stages are egg nymph and adult. With
okhers-those that undergo complete metamor-
phosis or change-fodr divisions are evident
egg. larva, chrysalis and adult.
For illustration let us take the sugar beet
leaf hopper Of the West, destroyer Of sugar beet
crops. This insect carries with it . poison in
its feeding that is destructive to the sugar beet
after the manner Of the poison Of the malarial
mosquito to man. This hopper has three
stages Of development-the egg. nympy and
adult. It lives through the Winter on wild
host plants in the desert area Of the West and
when Spring comes, along the latter part OF
May, it begins to move on the cultivated beet
fields, having exhausted the food possibilities
of the host plant The peak Of its population
b in June or July
In the beet areas determination of what hap
pens during the Winter as regards this hopper
Is followed up, and upon the basis Of this
Information sugar beet growers are advised as
to planting crops. Cone bags are suspended
from tall poles during the late Summer migra-
ton period, and the hoppers caught are sexed-
sex determined counted. Intensity, di-
rection and other physical factors in the life
Of the migrants such as temperature and wind
velOcities, are recorded.
Sugar beet insectaries, or bug houses" are
now employed to bring the hoppers through
the Winter specially adapted for their propa-
CATION Here the migratory croSS-Secnon feeds
upon the tender, succulent leaves Of the sugar
beet, hibernates and in the Spring breeds and
multiplies. The Springtime augmented brood,
like the Fall brood, is counted and sexed. This
cycle of observation gives the scientist the rate
OF increase, the proportion Of each sex, the
mortality rate Of the migrants and such other
data as go to make complete record Of the
Life history Of this plant enemy.
With this information in hand the leaf
hopper is at the mercy of the scientist 1t Is
only necessary now for him to determine the
"lethal gas" that will obliterate this pest from
the scene, designate the time Of its applica-
tlon and apply it.
I Ultimate control appears to be chemical
~ control-more than likely from the air in
the form Of sprays as great sweeps OF terrain
can be reached and covered by this means in
relatively short periods of time.
In the moth family four stages af develop
nent are recorded-egg, 1arva Caterpillar or
Warm), pupa or chrysalis and adult. This in
sect does its feeding and growing in the
larval stage. Poison therefore. just about
Matching time destroys it. Or the cocoon on
t1he ground can be buried
Checking upon the life history Of the great
berry moth, q moth ravishingly damaging to
grapes, presents again the interesting man.
ner In which science Is fighting our food
bastles, this time with q different foe in
kind With different habits Of living and de-
velopment.
large number Of wormy grapes are clipped
from vines at the beginning Of the study. These
ass put in cages with grape leaves, called
our familiar bug houses" or insectaries.
These are cylindrical wire baskets which hold
from one to one and one-hah quarts each.
These baskets are now placed in glass battery
jars, which have been supplied with about
one-haf inch Of sand In the bottom. This
sand absorbs the juice from the infested grapes
and maintains a fairly constant humidity in
the jars. The Jars are now closed with cloth
0overs.
When the larvae pupates or enters the CO.
coon stage of development the leaves bearing
ths cocoons are removed each day and fresh
Qpss supplied The cocoons are placed In small
~ glasses until the moths emerge. The