PRESS BULLETIN No. 293
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
THE FALL ARMY WORM, OR GRASS WORM
J. R. WATSON
Florida just now is experiencing a state-wide and serious
outbreak of the fall army worm. As usual, the damage is local;
crops on some farms suffering severely while others escape.
The caterpillars when full-grown are about 11/ inches long,
brownish-green in color with black and yellow stripes running
lengthwise of the body. A yellow line down the middle of the
back forks at the head and becomes quite white, making a con-
spicuous V-shaped mark. The body is covered with small black
elevations which bear short, stiff, black hairs.
When abundant the worms quickly consume all vegetation
where they hatched and then move on to fresh fields. It is these
crawling colonies that give the insect the name, "army worm,"
In these armies one may usually find worms ranging in size from
less than a fourth inch to full-grown.
The first choice of the worms for food is the tenderer
grasses, such as Bermuda and crab grass, but as food becomes
scarce they will attack almost any field crop. They are now
severely damaging cowpeas, peanuts, velvet beans, castor beans,
and late corn.
The quickest remedy to apply, and probably the cheapest
for most farmers, is the Kansas bait, which for several years has
been in successful use against grasshoppers and cut worms. In
tests at or near the Experiment Station the bait has been found
to work equally well against the sweet-potato caterpillar and
the fall army worm.
To make this bait, mix together thoroly 20 pounds of bran,
5 pounds of cottonseed meal, and 1 pound of paris green. Then
grate or chop finely, rind, pulp and all, 3 or 4 lemons into 21A/
gallons of water. Oranges or grapefruit will do, but lemons or
limes are better. Dampen the dry bran and paris green mix-
ture with this liquid until the whole mass is moist but not
sloppy. It should be of such consistency that it will fall in fine
flakes when sown broadcast over the vines. Last of all, knead
into the mixture 2 quarts of molasses or syrup. This should be
thoroly worked into the mash.
Instead of the mixture of bran and cottonseed meal, bran
alone may be used. If wheat bran can not be obtained barley
or rice bran may be substituted. Bitter molasses such as New
Orleans, stale bran or meal, should not be used in making this
July 25, 1918
bait.. Make up the bait fresh each day. The amount provided
by the foregoing formula should be sufficient for a field of four
or five acres.
Poisoned mash should be put out either in the evening or
early morning so that it will not dry too quickly. In the even-
ing would be better as the caterpillars would have longer to
feed upon it before it becomes dry. If properly sown it will fall
in such small flakes that there will be no danger to fowls or
wild birds picking it up.
SPRAYING OR DUSTING
If the farmer has a good spraying machine and water is
handy he may find it cheaper or more convenient to spray his
crops. For this purpose use one of the arsenical compounds.
Or the arsenical may be applied dry, as a dust, mixed with some
inert substance such as flour, cottonseed meal, road dust, ashes,
or perhaps best of all, air-slaked lime.
Paris green is the cheapest of these compounds. One pound
to 150 gallons of water is sufficient. Two pounds of lime should
be added to prevent burning. But even with the lime, paris
green will often seriously burn many plants, especially beans.
In the dry form, 1 pound is used with 50 pounds of flour or lime.
Arsenate of lead is less liable to burn plants than paris
green, but is somewhat more expensive, as it is necessary to use
double the amount. This and arsenite of zinc come in two forms
-a powder and a paste. The paste is intended for use with
water as a spray. Three or four pounds should be used to 100
gallons of water. One half of this weight of powder is sufficient.
The newest insecticide, calcium arsenite, if obtainable, will
probably prove satisfactory on grass and other hardy plants. It
is more liable to scorch plants than is arsenate of lead, but is
Plants sprayed or dusted with any of these arsenicals, and
especially paris green, should not be fed to stock until they have
been washed by one or two good rains and at least three weeks
Sometimes a crop toward which the army is moving can
be saved by digging a ditch with perpendicular sides between
the army and the crop. A log dragged along this ditch will
crush the worms.
When full-grown the caterpillars enter the soil and, just
beneath its surface, change into pupae which are about half an
inch long. In about a week the adult emerges. This is a moth
with yellowish-gray fore wings and white transparent hind
wings measuring about 11/4 inches across. The moths fly by
night. The females lay their eggs on a variety of plants, but
State papers please copy.