They usually feed on plants in the nightshade or Solanaceae family, which includes Datura, Nicotiana, tomatoes,
eggplant, potatoes, peppers and those species considered weeds, such
as bittersweet nightshade (Solanum dulcamara). These plants are high in alkaloids that
make them toxic to animals, including people.
Leaves are stripped-off to mid-vein of the leaf
One of Penn State's doctoral candidates, Tim Morton, is doing
research on these insects. He has found that the alkaloid content of
their excrement is key to their survival. When he removed the
excrement from the larvae or fed them an innocuous diet of lettuce,
predators made short work of them. Those consuming their preferred
diet of nightshade were unharmed.
The adult beetles are reddish-yellow with three black stripes
running lengthwise down their wing covers. They become active when
tomato and potato plants (or other preferred crops) are planted out
in late spring or early summer. They lay clusters of small yellow
eggs on the underside of leaves. When the larvae hatch, they begin
feeding on the foliage. They are able to coat themselves with
excrement because their anus is in the middle of their backs. They
feed for about two weeks and then drop to the ground to pupate.
Control options include removing severely infested leaves and
crushing the insects or sealing them tightly in a plastic bag and
sending them out with the trash. You can also make insecticide
applications to control them. Rotenone, pyrethrins and Sevin (carbaryl)
are labeled to control three-lined potato beetle.