SWEETPOTATO WEEVIL

A, Weevil infested sweetpotato and crown of plant; a, adults; b, larva; c, pupa; d, larval injury; e, exit holes; f, feeding and egg punctures. B. Developmental stages. (A, about natural size; B, about five times natural size.)

SWEETPOTATO WEEVIL

The sweetpotato weevil lays its eggs in small holes that it makes in the stems of sweetpotato plants or directly in the potatoes. 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 reaches its full growth.

While in the stem or potato, the grub changes into the pupa, or resting stage, which lasts 7 or 8 days before the weevil emerges.

The adult weevils injure the sweetpotato plant by feeding on the leaves, vines, and roots. The grubs do damage 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 developed weevils when they emerge from the sweet-potatoes. 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 Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina, and Texas.

Control: If infestations are light, the pest can be eradicated if it is deprived of its food for about 1 year. The procedures are:

1. Plant no sweetpotatoes for 1 year in a zone extending 1/2 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, dust it with 10 percent DDT dust at the rate of 1 pound to each 1,600 square feet of surface area. If a spray is desired, add 8 pounds of 50 percent DDT wettable powder to 100 gallons of water. Apply the spray at the rate of 1 1/2 gallons to each 1,000 square feet. (c) At harvest remove all sweet-potatoes 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 sweetpotato fields at least twice during the winter.

In commercial areas where fields are generally infested with the weevil, effective control may be bad by the following practices:

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.

Follow clean-up practices given for light infestations (2, b and c).

Destroy plants and tubers in seedbeds as soon as you have produced enough plants. Rotate field plantings. Do not follow sweetpotatoes with sweetpotatoes.

Plant the new crop as far away as possible from the crop of the previous year.