These plants develop dark green, water-soaked spots that turn tan, dark brown, or black with a yellow border. Spots can enlarge enough to cover an entire leaf. Stems and petioles can also be infected. Nematodes are tiny roundworms that live in and feed on plant tissues, especially roots. Infected plants are often stunted, have leaves with brown lesions, and roots with nodules.
Good sanitation including soil sterilizations helps to control nematodes.
Stunting can also be seen. There is no control except to eliminate diseased plants. Spread of these diseases from one plant to another is unlikely. Powdery Mildews Powdery mildews are often found on grape ivy, kalanchoe, begonias, or pileas. A white growth appears on leaves, flowers, or stems that does not usually kill the plant, but reduces its quality.