.- Everglades Station Mimeo Report 60-4 September 15, 1959
A Preliminary Report On
The Corn Stem Weevil And Its Control
By Emmett D. Harris, Jr.*
Young sweet corn plants were heavily infested last year by small white leg-
less grubs "boring" or "mining" within the stem near the ground level. Fifty
percent or more of the fields in this area were affected. In many fields nearly
100 percent of the plants were attacked. Many infested plants were stunted,
lodged in heavy winds, or wilted and died, but some showed no obvious evidence of
injury. Although it has not been completely shown in controlled experiments, the
grubs appear to cause this damage.
This insect, Hyperodes humilis (Gyll.) had not been known to damage crops
before and does not have a common name although it has been found in the United
States for many years. Because of its feeding habits "corn stem weevil" seems to
be a good name.
Eggs about 1/32 inch long are usually imbedded in the tissue of the sheath
of the lower leaves on young corn plants. They are more easily seen when the
leaf sheath is stripped from the plant and examined from the under surface. They
are creamish white when first laid but in a day or two change to dark brown.
They hatch in about three to six days.
The grubs are white with a light brown head and legless. They are about
1/32 inch long when first hatched and about 1/4 inch long when mature. They feed
about 20 to 25 days before they become pupae. The pupal stage is one in which
the insect is inactive and is changing from a larva&. to an adult.
The pupa is white and about 5/32 inch long. Pupae have not be ..
the field, but grubs reared in the laboratory pupated in corn sta ~ About four
nSE 29 1959
to nine days are spent in the pupal stage before the adult insect \jrges. A
SAssistant Entomologist, Everglads Experiment Station, Belle Glade
* Assistant Entomologist, Everglades Experiment Station, Belle Glade
The adult weevil is about 5/32 inch long and dark brown with white scales.
It has a long snout. Adults seem to be active at night and to spend the daylight
hours in the soil near the young corn plant.
Grubs also have been found attacking field corn and sorghum. Eggs have been
found on goosegrass, Elusine indica (L.) Gaertn., and nutgrass, Cyperus rotundus L.
Budworm control programs using toxaphene, DDT, heptachlor, or mixtures of
these chemicals with parathion have not controlled this pest. The best control
known at present is to apply one gallon of DDT 25 percent emulsifiable in 100
gallons of spray every four days, beginning on the day that the first young corn
seedling emerges. This schedule should be followed for about seven applications
or until the corn is about one month old. At this age the plants seem to be less
attractive to egg-laying weevils and less susceptible to grub damage. The first
three sprays can be applied at 50 gallons per acre using two overhead nozzles.
Thereafter, four nozzles should be used with the lower two aimed to hit the lower
part of the stem and the soil near the plant. At this time 100 gallons per acre
should be applied. Guthion at a dosage of one pound of actual toxicant per 100
gallons of spray has also been very effective but at present is not commercially
available for use on sweet corn. This program also should give excellent control
As these recommendations are the result of only one season's studies they
probably will be changed somewhat as more information is obtained about this pest
and its control.