PRESS BULLETIN 198
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
THE SOUTHERN GRASS WORM, OR FALL ARMY WORM
By J. R. Watson
The northern and western sections of Florida, together with the gulf
coast of Alabama, ha'e been seriously troubled this season by an outbreak
of the fall army worm. It is exceptional for this early brood to appear in
such large numbers, and the destructive armies usually belong to the later
brood (which comes during late July and in August), or to still later ones.
It is this that has given rise to the name of "fall army worm."
The unusually large numbers of the early brood this year may possibly
result in an even more disastrous outbreak in August. Such a consequence
is, however, by no means certain, as enemies or weather conditions may
bring the pest under control by that time. Nevertheless it will be prudent
for the farmers in the infested areas and neighboring localities to be on
the lookout for the caterpillars, and to prepare to fight them on their first
Methods of Control
On field crops one can best use some of the arsenical compounds. These
can be applied either with water as a spray, or dry as a dust; or 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 gal-
lons 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 one 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
July 6, 1912
paste is intended for use with water as a spray, and three or four pounds
should be used to 150 gallons of water.
The newer insecticide, arsenite of zinc, will probably prove most satis-
factory of all if it can be obtained. It is less liable to burn plants than
even arsenate of lead, is cheap, sticks better, and is not very poisonous to
man or domestic animals. However, plants sprayed with any of these, and
especially Paris green, should not be fed to stock until they have been
exposed to one or two good rains.
In a garden, or even in a small corn patch, perhaps the most practical
way to combat this pest is by hand-picking. In the early morning, or about
sunset, one can go into the garden with a wide-mouthed dish containing a
little water with a film of kerosene, and knock all the caterpillars that can
be found into this. The kerosene will kill the worms. Three or four
pickings will usually rid the garden of the pest.
On forage crops it is usually best to mow the field'at once, and save
the forage. When the hay becomes dry the caterpillars will not trouble it.
Description and Life History
This insect is also known as the Southern army worm. Its scientific
name is Laphygma frugiperda. The caterpillars are nearly full-grown before
they collect in armies and attract attention. They are then about one and
a quarter inches long; and are brown, with a yellowish-gray stripe down
the back and a narrower brownish-black one along each side. On the head
there is a conspicuous V-shaped white mark. The body is covered with
small black prominences, from each of which a short stiff black hair arises.
When full-grown, the caterpillars go into the ground, and change just
beneath the surface into pupae which are about half an inch long. The in-
sects of the last fall brood remain in the ground all winter, but in summer
the moths emerge in about a week. They have yellowish-gray fore-wings,
and white, almost transparent, hind-wings. They measure about one and a
quarter inches across. The moths 'fly by night. The females may lay their
eggs upon a large number of different plants, but seem to prefer grasses.
Grasses and small cereal grains also form the first choice of the larvae,
and corn comes next. The large armies of caterpillars, when food is scarce,
devour nearly all green succulent plants. The eggs are placed in masses of
fifty or more, and are covered with the mouse-colored hair from the body
of the female. They hatch in about ten days.
State papers please copy.