By Barbara Fahs, Garden Guides Contributor
Introduction to Sweet Potato Weevils
If you grow sweet potatoes, you might encounter this destructive insect having lunch on your plants. The sweet potato weevil lives in warm climates, such as the Gulf Coast, Hawai'i and Puerto Rico. The larva is the most destructive phase: it is white, legless and about 1/3 inch long. Adults are colorful, with blue wing covers and orange or red bodies. Less than 1/3 inch long, they have a long, thin head and body, resembling an ant.
Prevention and Control
Buy only certified weevil-free slips or seed potatoes. Mound soil around stems, which deters larvae from entering the roots. Clean up the garden area at the end of the season, and then rotate where you plant them the following year.
Besides sweet potatoes, this weevil also eats members of the morning glory family in the wild but no other vegetable crops.
Sweet potato weevils are the most serious pest of the plant after which it is named. If your vines are infested, you'll begin seeing yellowing of the plant. They're easy to overlook, so pay attention to any changes in your plants, because the tuber, once harvested, will be spongy looking and ruined with holes due to the larvae tunneling into the edible roots.
Ants and several species of parasitic wasps show promise as natural enemies of the sweet potato weevil. Studies have shown that a type of nematode penetrates the soil and underground tubers and kill larvae.
Pheromones have been used to decrease adult populations of the weevil, as this type of control disrupts mating.
Other Methods of Control
After harvest, crops can be treated with chemical fumigants or irradiation to prevent damage in storage. When potatoes are stored in atmospheres with low oxygen and high carbon dioxide, the weevils will perish.