The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
COOPERATIVE EXTENSION WORK
AGRICULTURE AND HOME ECONOMICS
UNIVERSITY OF FLORIDA DIVISION OF AGRICULTURAL
EXTENSION AND UNITED STATES DEPARTMENT
OF AGRICULTURE COOPERATING
P. H. ROLFS, Director
KILL CORN WEEVILS
By A. P. SPENCER
1. A crib of corn will be entirely destroyed, if left to the
2. Of the 12,600,000 bushels produced in 1916, it is esti-
mated that 10 percent or more of it was destroyed by weevils,
or about 1,260,000 bushels.
3. Weevils begin their work in the field. The eggs are
laid in the soft kernels, which may hatch in 6 to 10 days or
may not hatch for 6 weeks if cool weather prevails. A new
generation is produced about every 3 or 4 weeks, so by spring
several generations will have been hatched, unless the first
brood is killed. By these successive hatchings a large number
of weevils is produced even tho there were only a few when the
corn was gathered.
4. In order to get weevil-resistant corn, select the seed in
the field from heavy ears having shucks that fit closely over the
end of the ears. A closely fitting shuck keeps many weevils out.
5. The crib should be cleaned of all damaged and weevil-
eaten corn before storing the new crop. This old corn is a
source of infection.
BULLETIN 10 COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
One Sound Ear of Corn Is Worth Two Weevil-Eaten Ones
TREATED AGAINST NWEEVILS
HUSK I IRN- u
Corn weevils lay their eggs in the grain before the
corn is mature in the field. Varieties of corn having an
open shuck usually have more weevils than those with
a heavy shuck that comes well over the end of the ear.
The corn should be shucked in the field; this will leave
most of the weevils in the shuck instead of bringing
them into the crib with the corn. The shuck is no pro-
tection to the grain after it is placed in the crib, but
rather, it interferes with successful fumigation.
PREPARING TO FUMIGATE
Carbon bisulphide is the only material required for
fumigation. Be sure that the room, or crib, is tight-
the nearer air-tight the better. The gas given off by the
chemical kills the weevils, and this must not be allowed
to escape. The crib should be ceiled, have a tight floor,
and closely fitting windows and doors. The amount of
carbon bisulphide to use depends on the size of the crib,
and not on the number of weevils or the amount of corn
in the crib. The material evaporates readily and forms
a heavy gas which penetrates downward thru the corn,
killing all insect life. There must be sufficient gas
formed to fill the room, otherwise the air will dilute the
gas and the weevils will not be killed. They must be in
contact with the gas for 30 minutes or more.
APPLYING THE CHEMICAL
Use 2 pounds of carbon bisulphide for every 100
cubic feet of space in the crib; that is, if the inside di-
mensions of the crib are 8x10x5 ft., or 400 cubic feet,
8 lbs. of carbon bisulphide will be needed. If the crib is
not tight, increase the dose accordingly. The carbon
"u no.pndisli es aLu hope-ndnd these placed
on top of the pile of corn. Repeat the dose every four
to six weeks. One fumigation is usually not sufficient, as
weevils will continue to hatch from eggs not destroyed.
FUMIGATE IN WARM WEATHER
Carbon bisulphide is most effective in warm air.
For fumigating, choose a warm day when the tempera-
ture is 75 degrees F., or higher. Begin the fumigation
in the morning so that the full effect of the gas will be
TREATING SMALL GRAINS
Peas, oats, millet, sorghum seed, etc., can be suc-
cessfully treated against insects with carbon bisulphide.
Small quantities of seed can be best treated in barrels.
Fill the barrels within six inches of the top, place one-
half teacupful of carbon bisulphide in a saucer on top
of the seed, cover the barrel with heavy paper, and
fasten down the top, making it air-tight. After 24 hours
the barrel may be opened.
EFFECT ON GERMINATION
If the grain is thoroly dry and mature, this fumiga-
tion will not injure germination even if used much
stronger than is here recommended. But if the grain is
moist or soft the germ may be injured.
When corn is placed in a tight crib it passes thru
a sweat, causing some heat which forms a vapor. The
treatment should not be applied until after this heating
stage is passed, as the two gases combined may injure
Caution.-Carbon bisulphide gas is inflammable.
Keep lights and fires away.
FOR FURTHER DETAILS ASK YOUR COUNTY AGENT
Or Write, Extension Division, University of Florida, Gainesville