PRESS BULLETIN No. 304
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
J. R. WATSON
Brown, velvety caterpillars are sometimes very destructive
to sweet potato plants during late July, August, and early Septem-
ber. Often, they strip the leaves from an entire field of vines.
They usually appear first in spots in the field. If not checked, the
caterpillars will spread from these spots to the whole field, travel-
ing after the fashion of army worms to which they are closely
related. In fact one species is sometimes called the "semi-
tropical army worm".
] Altho the defoliated vines may put out new leaves and
continue to grow after the worms have passed, the yield of
tubers is always greatly reduced, and may be entirely destroyed
as a result of the attack.
CONTROL BY POISONED BAIT
The quickest, and for most farmers the cheapest, method of
controlling these caterpillars is by means of the "Kansas bait",
which has been used so successfully against cutworms as well
as grasshoppers for which it was originally made.
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 21/2 gal-
lons of water and add 2 quarts of molasses. Oranges or grape-
fruit will do, but lemons or limes are better. Dampen the dry
bran and paris green mixture 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.
This poisoned mash should be put out either in the evening or
early morning so that it will not dry too quickly. In the evening
would be better as the caterpillars would have longer to feed
upon it before it becomes dry. If properly sown it will fall in
February 22, 1919
such small flakes that there will be no danger to fowls or wild
birds picking it up.
Instead of the mixture of bran and cottonseed meal either
may be used alone, in which case 25 pounds are required. Bitter
molasses such as New Orleans, stale bran or meal, should not be
used in making this bait. The bait should be made up fresh each
day. The amount provided by this formula should be sufficient
for a field of four or five acres.
CONTROL BY SPRAYING
If one has a good power spraying machine he can economi-
cally spray the vines with lead arsenate, using 1 pound of the
powder to 2 pounds of the paste, mixed with 50 gallons of water.
It is well to add to the mixture the milk obtained by slaking 2
pounds of quick lime in hot water and then straining it. This will
prevent any burning of the leaves, otherwise possible, by the
CONTROL BY DUSTING
A cheaper method of control is to dust the plants in the
early morning when they are wet with dew, using a mixture of
powdered arsenate of lead and thoroly air-slaked or hydrated
lime. Use from two to four times as much lime as arsenate.
This mixture can be applied by means of a coarse burlap bag,
shaken over the vines, but a better method is to use a dusting
machine designed for such work.
Fall army worms also sometimes strip sweet potato vines.
The foregoing measures will serve to control them as well as
grasshoppers which always do more or less damage to this crop.
Birds are important enemies of nearly all caterpillars. The
insect-eating wild birds on the farm should be carefully protected
from hunters and cats. Domestic fowls, especially turkeys, eat
many caterpillars and will quickly check an outbreak of these
insects if given the run of the field. If fowls are housed in
portable' colony houses, the houses may be moved to the edge
of the infested field. The caterpillars make a good poultry food,
materially reducing the feed bill.
State papers please copy.