This pest affects crops in the southern United States. The larvae -- 1/3-inch-long, legless white grubs with dark heads -- tunnel through sweet potato roots and vines. The adult weevil is 1/4 inch long with a pronounced snout. Adults feed on the tops of the plant, but usually do little damage. They lay eggs in cavities in the potato or on the vine near the soil surface. Weevils overwinter in stored sweet potatoes or on nearby weeds such as wild morning glory. There can be as many as eight generations per year.
When buying slips or seed potatoes, make sure they are certified weevil-free. Mound soil around the base of stems to make it difficult for larvae to enter roots. Clean up all weeds and leftover sweet potatoes at the end of the season. Rotate crops.
Photography by Scott Bauer, USDA Agricultural Research Service, Bugwood.org