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.
Affected Plants
Besides sweet potatoes, this weevil also eats members of the
morning glory family in the wild but no other vegetable
crops.
Damage
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.
Predator Insects
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.
Natural Insecticides
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.
