Ornamental sweet potato vines (Ipomoea batatas) are fast plants which produce lobed leaves, fleshy roots and tubular flowers that resemble morning glories. Unlike edible crop varieties, “Tricolor” and other ornamental cultivars produce roots that lack taste. Hardy at U.S. Department of Agriculture plant hardiness zones 9 through 11, sweet potato vines thrive in well-drained, moist soil and full sunlight or shade. Beetles, caterpillars and other insect pests may bother these plants. Always follow label directions and precautions when you use pesticides to control insects.
Beetles
You may see adult beetles feeding on sweet potato vine leaves. Examples include cucumber beetles, which quantify 1/4 inch long and have green bodies with dark spots or green bands, and miniature flea beetles, which quantify 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 which expand and disfigure the roots. Natural predators, like tachinid flies, and pesticides, such as pyrethrum, help control beetles.
Caterpillars
The leaf miner is a moth caterpillar that feeds on the delicate green tissue within the leaves. The grayish adult moth steps 1/5 inch long and sets greenish white eggs on the leaf surface. Infested leaves develop silvery monitors or mines and turn brown as the 1/4-inch-long, segmented caterpillar travels and feeds on plant tissues. The 1/10-inch-long, brown pupae could be visible within webbing on the undersides of their 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 control caterpillars.
Sucking Insects
Aphids and silverleaf whitefly nymphs step less than 1/10 inch long and feed on the juices of sweet potato stems and leaves. 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. Because honeydew covers the leaves, black sooty mould grows and interferes with photosynthesis. Infested sweet potato vines develop yellow, curled leaves and become stunted. Remove the bugs by hand and allow woman beetles and other natural predators to control whitefly and aphid infestations.
Sweet Potato Weevil
The sweet potato weevil is among the most dangerous sweet potato vine insects, notes the International Potato Center. The white, legless larvae have brown heads and quantify 1/4 inch long, and an adult steps 1/4 to 1/3 inch long and has an orange body and metallic blue head. Adult weevils feed on all plant parts, however, the larvae tunnel through the roots, in which they produce 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 in previous plantings, and destroy daytime glory weeds, which are alternate hosts.