SWEETPOTATO WEEVIL 
( Cylas formicarius elegantulus (Sum.)) 
Life History and Injury 
The sweetpotato weevil is the most destructive insect pest attacking the 
sweetpotato crop. The adult weevil lays its eggs in small holes, which it punc- 
tures in the plant stems near the surface of the soil, or directly in the potatoes 
when it can reach them. In about a week the eggs hatch into small, white 
grubs, which feed and grow in the vines or in the potatoes. In 2 or 3 
weeks the grub is fully grown and about three-eighths of an inch long. While 
in the stem or potato, the grub changes into the pupa, or resting stage, which 
is white and slightly smaller than the grub. After 7 or 8 days the adult weevil 
crawls out of its pupal skin and emerges from the sweetpotato plant to feed 
and mate. The females are then ready to lay eggs for another generation. 
The weevils are about one-fourth of an inch long and, because of their long legs 
and slim body, look like large ants. If the weather is favorable, the weevil may 
live for several months. 
The adult weevils injure the sweetpotato plant by feeding on the leaves, vines, 
and roots, and the grubs by feeding within the stems, roots, and potatoes. Small 
holes in groups on the surface of the potatoes are either feeding marks or holes 
made by females in laying their eggs. Larger holes are made by newly devel- 
oped weevils when they emerge from the sweetpotatoes. If weevily potatoes 
are cut open, the grub-made tunnels can be seen, often with grubs or pupae in 
them. Infested sweetpotatoes have a bitter taste and are unfit for food. 
The weevil is known to exist in sections of Alabama, Florida, Georgia, 
Louisiana, Mississippi, South Carolina, and Texas. 
Prevention, Eradication, anti Control 
Most infestations of the sweetpotato weevil are established in new areas when 
sweetpotato plants, seed, or table potatoes are brought in from infested areas. 
Quarantines are maintained in the principal sweetpotato-growing States to 
prevent introduction of the weevil, and by States in which it is present to pre- 
vent further spread and to assist in its eradication and control. Most States 
maintaining quarantines permit entry of commercial sweetpotatoes from 
infested areas only when the stock has been fumigated with the prescribed 
dosage of methyl bromide. The United States Department of Agriculture is 
cooperating with the States in the control and prevention of spread of this 
weevil. 
In areas where infestations are light the pest can be eradicated if it is 
deprived of its food for about one year. The procedures are as follows: 
1. Plant no sweetpotatoes for one year in a zone extending Vz to 1 mile 
from any known infestation. 
2. On infested farms: (a) Dispose of all remaining sweetpotatoes by 
February 1 or earlier by dehydration, feeding to livestock, or burning. 
(b) Immediately after cleaning up the storage place, treat it with a 
DDT spray. Use either an emulsion concentrate or a wettable powder, 
diluted with water to contain the equivalent of Vz pound of technical 
DDT in each IVz gallons of spray. Apply the spray to all surface areas, 
stopping before it begins to run off. (c) At harvesttime remove all 
sweetpotatoes from the field and do not store infested potatoes. Destroy 
all roots, crowns, small sweetpotatoes, scraps, and volunteer plants. 
Graze livestock on the field after harvest if possible. Plow old sweet- 
potato fields at least twice during the winter. 
In commercial areas where fields are generally infested with the weevil, 
effective control may be had by the following practices: 
1. Use State-certified seed sweetpotatoes. If seed is selected locally at 
harvesttime, treat it thoroughly with 10-percent DDT dust at the rate 
of 1 pound to 6 to 8 bushels of seed and store the seed away from any 
food products for man or animals. 
2. Follow clean-up practices given for light infestations (2, b and c ) . 
3. Destroy plants and tubers in seedbeds as soon as sufficient plants have 
been produced. 
4. Rotate field plantings. Do not follow sweetpotatoes with sweetpotatoes. 
Plant the new crop as far as possible from the sweetpotato crop of the 
previous year. 
CAUTION. Do not let DDT sprays and dusts reach any food products for 
man or animals. DDT is poisonous and should be handled with care. Store 
it in a dry place where children and animals will not have access to it. 
July 1949 U. S. Government Printing Office 
For sale by the Superintendent of Documents, Washington 25, D. C. Price 5 cents 
"it U. S. GOVERNMENT PRINTING OFFICE : 1949 838907 
