Plant Health Problems
Diseases caused by Fungi:

Fusarium root and stem rot, Fusarium spp.
The disease is caused by fungi that persist in the soil for long periods of time. Symptoms include a dark tan rot that extends into the root and usually has a sharp line separating the rot from the healthy portion of the root. Stem infections appear as swollen areas at the base of the stem that have internal vascular discoloration.

The disease can be avoided by practicing two-year rotations out of sweet potatoes and by using clean planting material.

Black rot, Ceratocystis fimbriatum.
Tubers with this disease show irregular sunken spots, dark brown to black in color. Very often black dots are scattered across the spots. These black dots contain the spores of the fungus causing the disease. Pink masses of the spores are sometimes seen oozing from the black dots. The disease is not very troublesome on sweet potatoes grown in Connecticut.

To avoid the disease, choose healthy sprouts or tubers for planting, practice crop rotation, and use extra care in storage.

Soft rot, Rhizopus nigricans.
Sweet potatoes in storage are commonly infected with the bread mold fungus, which causes a watery soft rot of part or all of the tuber. The fungus may be seen as a fluffy, white growth, with black dots supported on threads.

Throw out any tubers which show soft rot, and air out the rest of the sweet potatoes in a warm room.

Insect Problems:

Aphids.
The green peach aphid sometimes infests sweet potatoes. See Aphid fact sheet.

Blister beetles. Family Meloidae.
Several species of blister beetles occasionally feed upon the leaves of sweet potatoes. Several species of large, active, slender, soft-bodied beetles may occasionally feed on the greens. They are usually dark colored and may have thin white lines on their wingcovers. The larvae live in the soil where they feed entirely upon grasshopper eggs. Control is not usually necessary.

Tortoise beetles.
Several species of tortoise beetles and their larvae feed upon sweet potato. These insects are shaped like a tortoise shell with a protruding edge. The more common species in Connecticut are all small colorful beetles with prominent markings or bright, iridescent color. They are generally not abundant, and do not need control.