Evening star., 1935-05-19

Certain species are responsible for
crop diseases which cut our food
producing capacity to an extent which
| if it could be measured would be star
| ting and discouraging. One species,
the gall nema, attacks about 500 diff
| ferent kinds of plants, making gals or
knots on the roots which frequently
prevent the plant from producing a
profitable crop. Very few plants are
free from such attack, not even weeds,
which are often thought to be blessed
with immunity from enemies. Fortu-
nately the grasses, including the small
grains and corn, are less subject to
devastation than most of the other
growing things. BY using these resis-
tant crops in rotation it Is possible to
keep down the number Of pests in the
soil as the nemaS will die out in large
numbers if a crop, undesirable from
their standpoint, is grown on the
ground for a year or two.
Now here's the most astonishing
fact of all: Allowing two months
to each generation, pair of gall nemas
will have five to ten million descend
ants in six months, should all survive
Among the many crops attacked by
the destructive root knot nema. the
most important are alfalfa, clover,
cotton, COW peas, field peas. fax, fig,
grape, peach, soy beans, sugarcane,
sweet potatoes, tobacco. ornamental
plants and trees
Probably not one person in so re-
alizes that there are certain species OF
nema that infest different animals,
insects and man. The hookworm Is a
nema and there is one that infests
foxes that is blood red in color and
attains length of several feet. Micro
scope wizards are seeking to learn If
any of these peculiar parasites can be
used to combat certain insects of
economic Importance. Already 1t has
been found that certain nema has
prediction for grasshoppers and Fed
eral scientists believe that it is this
enemy in some cases which causes the
hopper" scourge to rise and subside
in great waves. This nema, which
attains length of 20 inches or more
and is about the thickness of a coarse
thread, makes the host insect sterile
and in that way enormously reduces
the grasshopper increase.
While studying the willy mosquito
under high-powered microscope, DIR.
T. j. Headlee, Federal entomologist,
thought up a unique idea for outwit-
ting the pesky stingers. This was a
trap consisting of an iron cylinder at
the front of which is mounted an elec-
trio light bulb, with reflector behind
and an electric fan back of that. A
| fine wire screen closes the rear of the
| cylinder. A cyanide collecting jar fits
into the cylinder just below and in
front of the screen. The cylinder is
equipped with a wind vane and is
mounted on a ball-bearing device, so
that always it faces the wind. An
ordinary 110-volt circuit supplies the
current for its operation. A clock
and switch device will turn the ma
chine on or of whenever desired.
COME 20 of these traps were OPP
- Grated under the general direction
of Federal entomoligists in the Chesa-
peake Bay region during the "stinger"
season. In a single night 5000 mosqui-
toes were caught. The traps were
used, the scientists say, not to control
the pest, but to obtain true picture
of It's prevalence. The Chesapeake
Bay survey discovered 28 different
species of mosquitoes varying widely
in habits and abundance. This insect
Sampling was the important prelfmi-
nary step in systematic control by
drainage, oiling and other means.
Certain microscope wizards of the
Department of Agriculture have been
having lot of fun lately watching
the fantastic maneuvers Of tiny worms.
They found that worm trying to
bore a hole through the hide Of an
animal needs something to push
against, just as a man does If he's
using an auger to bore a hole into
wall. If the mans footing Is slippery,
he cannot get along well with the work.
1t is the same with the kidney worm
that causes serious losses to swine
growers, particularly in the South,
parasitologists have found. The clean
skin of pig offers slippery footing for
the worm and he cannot bore In. But
just let the worm get on spot where
there is enough dirt so that he can
brace himself and he will find traction
enough to bore In and make plenty
of trouble.
Thanks in great measure to the
microscope, the screw-worm fly re-
sponsible for heavy live stock losses
in the Southwest, and more recently
in the Southeast, has been shown up