The Bugs on a Sweet Potato Vine
Ornamental sweet potato vines (Ipomoea batatas) are fast-growing plants that produce lobed leaves, fleshy tuberous roots and tubular flowers that resemble morning glories. Unlike edible crop varieties, Tricolor and other ornamental cultivars produce tubers that lack flavor. Hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11, sweet potato vines thrive in well-drained, moist soil and full sun or shade. Beetles, caterpillars and other sweet potato insect pests may bother these plants. Carefully follow label directions and precautions when you use pesticides to control insects.
Beetles and Their Larvae
You may see adult beetles feeding on sweet potato vine leaves. Examples include cucumber beetles, which measure 1/4 inch long and have yellow bodies with black spots or green bands, and tiny flea beetles, which measure 1/5 inch long and have long hind legs.
The larvae of these beetles cause more damage than the adults. White cucumber beetle and flea beetle larvae chew small holes that enlarge and disfigure the roots. Natural predators, such as tachinid flies, and pesticides, such as pyrethrum, help control beetles.
Sweet Potato Caterpillars
The leaf miner is a moth caterpillar that feeds on the soft green tissue inside the leaves. The grayish adult moth measures 1/5 inch long and lays greenish white eggs on the leaf surface. Infested leaves develop silvery tracks or mines and turn brown as the 1/4-inch-long, segmented caterpillar travels and feeds on plant tissue.
The 1/10-inch-long, brown pupae may be visible inside webbing on the undersides of the leaves. Reduced leaf surface results in fewer sweet potato roots. Other caterpillars that damage the vines include greenish black armyworms and greenish brown cutworms. Ants and other natural predators as well as the bacterium Bacillus thuringiensis (Bt) control caterpillars.
Sucking Sweet Potato Insects
Aphids and silverleaf whitefly nymphs measure less than 1/10 inch long and feed on the juices of sweet potato leaves and stems. Like other sucking insects, they gather in clusters on plant surfaces, drink the sap from plant tissue and excrete a clear, sugary substance called honeydew. As honeydew covers the leaves, black sooty mold develops and interferes with photosynthesis.
Infested sweet potato vines develop yellow, curled leaves and become stunted. University of California recommends that you remove the bugs by hand and allow lady beetles and other natural predators to control whiteflies on sweet potato vines, as well as aphid infestations.
Sweet Potato Weevil
Louisiana State University Agricultural Center advises that the sweet potato weevil is one of the most destructive sweet potato pests in the field, as well as in storage. The white, legless larvae have brown heads and measure 1/4 inch long, and an adult measures 1/4 to 1/3 inch long and has an orange body and metallic blue head. Adult weevils feed on all plant parts, but the larvae tunnel through the roots, where they create exit holes as adults.
As the larvae feed on the roots, the vine develops wilted leaves, dieback and stunted growth. Remove volunteer seedlings and debris from previous plantings, and destroy morning glory weeds, which are alternate hosts for these sweet potato pests.