Brown to black water-soaked spots on leaves and stems. Foliage will turn black, a gray mold grows on the undersides of the leaves and tubers will rot. Avoid overcrowding of plants. Dispose of infected plants in the garbage immediately. Especially the undersides of the leaves.
Foliage is eaten.
Long, slender, black or grayish beetles, or black beetles with narrow yellow or gray stripes cause this damage. They have a distinct head and their abdomen sticks out from under the wing covers at the back. This Beetle is a problem in northern Ontario. After blooming, lower leaves wilt. When cut a creamy yellow to light brown rot shows just beneath the skin.